This paper aims to review the nature and practice of earthquake reconnaissance missions since the earliest examples to today’s practice, and to try to show some of the ways in which the practice of earthquake engineering today has benefitted from field observations. To give some historical background, the nature of some of the earliest recorded field missions are reviewed, notably that of Mallet following the 1857 Neapolitan earthquake; the achievements of the UNESCO-supported missions of the period 1963–1980 are considered; and the nature and contributions made by several national earthquake reconnaissance teams (EERI based in the United States, EEFIT based in the UK, and more briefly the Japanese Society for Civil Engineering, the German Earthquake Task Force, and AFPS based in France) are reviewed. The paper then attempts to summarise what have been the most important contributions from the field observations to several aspects of earthquake engineering, particularly to understanding the performance of buildings, both engineered and non-engineered, including historical structures, to geotechnical effects, to gaining understanding of the social and economic consequences of earthquakes, and to loss estimation from future scenario events. The uses and limitations of remote sensing technologies to assess damage caused by an earthquake are considered. Finally, possible changes in earthquake field missions to meet anticipated future challenges and opportunities are discussed.
1.1 Introduction
Engineering progresses through innovation, through the development of theories to explain observed phenomena, and through testing of those theories in the laboratory and in the field. In the case of earthquake engineering, field observation assumes a particular importance, because the science which needs to be applied, both in estimating the ground motions to be designed for, and in predicting the performance of structures under these ground motions is still relatively poorly understood, and also because earthquakes occur in any one location so infrequently.
A decade ago, in his keynote address to the 12th European Conference on Earthquake Engineering (Ambraseys 2002), Nicholas Ambraseys quotes a colleague’s definition of the earthquake engineer as the professional who “designs structures whose shapes he cannot analyse, to resist forces he cannot predict, using materials the properties of which he does not understand, but in such a way that the client is not aware of it”. Ambraseys was pointing to the alarming fact that for all our scientific and technological achievements, earthquake losses keep increasing with time, stretching the credibility of the earthquake engineering profession: and over many years he strongly argued the need for more systematic learning of the lessons from past earthquakes to improve performance.
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The title of this talk is taken from the concluding remarks of Ambraseys’ Mallet-Milne Lecture (Ambraseys 1988), which emphasises the importance of field observation through post-earthquake reconnaissance missions, and identifies some of the most important roles of such missions:
It is increasingly apparent that the site of a damaging earthquake is undoubtedly a full-scale laboratory, in which significant discoveries can be made by keen observers - seismologists, geologists, engineers, sociologists and economists. As our knowledge of the complexity of earthquakes has increased we have become more and more aware of the limitations which nature has imposed on our capacity to predict, on purely theoretical grounds, the performance of engineering structures, of the ground itself or of a community. It is the long-term study of earthquakes and fieldwork that offers the unique opportunity to develop a knowledge of the actual situation created by an earthquake disaster… It is field observations and measurement that allow the interaction of ideas and the testing of theories….Much computer effort has been devoted to solving problems based on guessed parameters … more data from field observation and measurement are now required.
The major disasters which have occurred since those words were written have only served to demonstrate their validity, and there has, in the last 25 years, been a steady growth in the number and quality of field reconnaissance missions, and in the understanding gained from them of the essential aspects of earthquake actions, the behaviour of different types of structures, and the response of communities in different societies to large earthquakes. But many barriers to the achievement of effective post-event reconnaissance still exist, from organisational and funding difficulties to long delays in the implementation of field observations into design practice.
This paper aims to review the nature and practice of earthquake reconnaissance missions since the earliest examples to today’s practice, and to try to point out some of the ways in which the practice of earthquake engineering today has benefitted from field observations. To give some historical background, the nature of some of the earliest recorded field missions will be reviewed; the achievements of the UNESCO-supported missions of the period 1963–1980 will be considered; and the nature and contributions made by several national earthquake reconnaissance teams (EERI in the US, EEFIT in UK, the Japanese Society for Civil Engineering and others) will be reviewed. The paper will finally try to summarise what have been the most important contributions from the field observations to several aspects of earthquake engineering, particularly to understanding the performance of buildings, to geotechnical effects, to gaining understanding of the social and economic consequences of earthquakes, and to loss estimation from future scenario events. The future of earthquake field missions will be discussed.
The UNESCO field missions were interdisciplinary field missions in which engineers studied alongside geologists and seismologists, sciences which depend to a large degree on field observation and measurement, and much was gained from this collaboration. Since about 1980, such interdisciplinary missions have become less common, since the style and timing, as well as the funding of post-earthquake seismological investigations has become very different from that of earthquake engineering missions. A limitation of this paper is that it concentrates on lessons for earthquake engineering rather than seismology, which is a topic for another author.
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1.2 Early Field Investigations
Perhaps the earliest field investigation with a scientific purpose was that of De Poardi following the 1627 M = 6.8 earthquake in the Gargano Region on the Adriatic Coast of Southeastern Italy. The earthquake was destructive, with a maximum intensity Imax = X (MCS), and liquefaction along the coast; there was also a strong tsunami that inundated the low-lying coastland (De Martini et al. 2003). De Poardi’s map shows the towns and villages affected with different symbols to indicate the different levels of damage (Fig. 1.1). Fish are depicted being thrown out of the coastal Lesina Lake which was seriously affected by the tsunami, corresponding to contemporary eyewitness accounts which reported that the lake completely dried out for many hours after the shock and many fish were stranded. Thus Poardi’s map may claim to be the first macroseismic intensity map (De Martini et al. 2003, Musson, pers comm).
Fig. 1.1
De Poardi’s map of the damage caused by the 1627 Gargano earthquake (Based on De Martini et al. 2003, a forerunner of modern isoseismal maps)
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The 1755 Lisbon earthquake of course was the occasion for important studies of earthquake and tsunami effects, though since Lisbon, the primary focus of the disaster, was also the capital city these cannot properly be said to be the result of a reconnaissance mission. The Marques de Pombal, Prime Minister at the time, was given charge of the emergency management (as it would today be called), and reconstruction planning. One of his notable moves was the systematic collection of quantitative information on the degree of shaking and the effects it produced. His questionnaire, sent out to local officials and the clergy, included questions such as: How long did the earthquake last? How many shocks were felt? What damage was caused? Did animals behave strangely?, and was thus arguably the forerunner of today’s online Did You Feel It? questionnaires (Dewey et al. 2000). Another of Pombal’s actions was to order the reconstruction of the Baixa District, close to the Tagus, not in the closely-packed heavy masonry construction which had proved so vulnerable to the ground shaking, but with broad avenues and use of a braced timber frame construction (the gaiola system), which is still the main form of construction in that area today (Cardoso et al. 2013).
1.3 Mallet’s Investigation of the 1857 Neapolitan Earthquake
The most significant earthquake reconnaissance mission prior to the twentieth century was undoubtedly that of Robert Mallet, who investigated the effects of the 1857 Great Neapolitan Earthquake, and who in his subsequent report (Fig. 1.2) justifiably laid claim to have established the first principles of observational seismology (a term which Mallet was the first to use).
Fig. 1.2
Cover of Mallet’s report on the 1857 Neapolitan earthquake
×
Mallet, from Ireland, was by profession an engineer, having taken over his father’s Dublin foundry at the age of 21. Through involvement with the learned societies of the time, first the Royal Irish Academy and later the British Association, he became interested in earthquake mechanics, and wrote a paper in 1847 in which he set out a view (not in fact a new one, Musson 2013) that an earthquake consists in the transmission through the solid crust of the earth of a wave of elastic compression, and that this could explain the previously observed rotation of monuments in earthquakes. He was convinced that this theory could be used to locate the focus of an earthquake using the effects on buildings and objects at the surface, but he needed a large earthquake to test his hypothesis. This earthquake was to be the Neapolitan earthquake of 1857, a decade later; but before he undertook this field mission, he had made two other important contributions to seismology. The first of these was a large catalogue of over 7,000 historical earthquakes from 1606 BC to 1842, developed from a variety of sources, and accompanied by a map of global seismicity remarkable for its accuracy in identifying most of the earthquake belts known today (notably not the mid-ocean ridges). The second was a design for a seismograph; this was never built but may have influenced the design of Palmieri’s later working seismograph.
Mallet explains his purpose in undertaking the mission in the first chapter of his report (Mallet 1862), so elegantly expressed it is worth quoting at length:
An earthquake, like every other operation of natural forces, must be investigated by means of its phenomena or effects. Some of these are transient and momentary and leave no trace after the shock, and such must either be observed at the time, or had from testimony. But others are more or less permanent and from the terrible handwriting of overturned towns and buildings, may be deciphered, more or less clearly, the conditions under which the forces that overthrew them acted, the velocity with which the ground underneath moved, the extent of its oscillations, and ultimately the point can be found, in position and depth beneath the earth’s surface, from which the original blow was delivered, which, propagated through the elastic materials of the mass above and around, constituted the shock……
(There are) two distinct orders of seismic enquiry. By the first we seek to obtain information as to the depth beneath the surface of the earth at which those forces are in action whose throbbings are made known to us by the earthquake and thus to make one great and reliable step towards a knowledge of the nature of these forces themselves; and this is the great and hopeful aspect in which seismology must be chiefly viewed and valued. By the second order of enquiry we seek to determine the modifying and moulding power of earthquake on the surface of our world as we now find it; to trace its effects and estimate its power upon man’s habitation and upon himself.
Thus Mallet’s goals were both seismological and engineering; and the paragraph quoted can indeed be taken, as a statement of the general aims which have guided post-earthquake reconnaissance missions to the present day.
The arrangements made by Mallet for the field mission are instructive, and are set out clearly in the introductory Chapter of his report (Mallet 1862). The earthquake occurred on 16th December 1857, and began to be reported in England about 24th December. On 28th December Mallet wrote to the President of the Royal Society suggesting the importance to science of sending “a competent observer” and offering to undertake this himself, estimating the cost at £50. He received (with the support of Charles Lyell) approval on 21st January, spent the next 5 days getting letters of approval from the Royal Society, the Minister for Foreign Affairs and “some noble or eminent scientific persons” to assist his travel into the earthquake affected area, and departed on 27th January. He travelled overland through Paris and Dijon where he consulted with eminent geologists; arrived in Naples on 5th February, and had to wait for a further 5 days for approval from the King, setting off on 10th February, accompanied by “a trustworthy staff of persons”, including an interpreter, who he had recruited while waiting for permission.
Once in the field, his method of working was to make use of detailed observations of the effects of the earthquake: cracks in masonry walls, fallen and overturned objects, the size, orientation and displacement of which he used to estimate the direction of the earthquake wave and also its angle of emergence, and even the velocity of the ground shaking. For this purpose he used a series of mechanical equations governing the movement of objects given an initial impulse, and some hypotheses about the position, size and direction of cracking in masonry walls under an emerging earthquake shock. By his own admission it was in many places extremely difficult to make any sense of the chaotic damage visible, but he learnt to make use of a subset of buildings which were typical, suitably oriented, and standing away from adjacent buildings. By plotting the direction and strength of shock in a total of 78 locations, he found a strong convergence and was able to determine a focus (at Caggiano), and plot a series of isoseismals (his own term) (Fig. 1.3) showing areas in four categories, essentially: those destroyed, those heavily damaged with fatalities, those slightly damaged, and those where the earthquake was felt (Musson 2013). He also estimated the focal depth from his estimates of the angle of emergence which had a mean value of 10.6 km.
Fig. 1.3
Mallet’s isoseismal map of the 1857 Neapolitan earthquake (Mallet 1862)
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All of these deductions look reasonable today, but given what we now know about the complexity of ground motion and its effects on buildings, the method of deducing not only direction but also angle of emergence of the earthquake waves is questionable. The chronology of the journey and what was observed at each location is exhaustively recorded in the report, which when finally produced had more than 700 pages. Mallet was also able to commission a photographer, Alphonse Bernoud, to travel the same route later, taking the first earthquake damage photos. Figure 1.4 is a drawn reproduction of one of several hundred also published with his Report, many of them designed to be viewed stereoscopically.
Fig. 1.4
Drawing, based on photograph, of damage in Polla from Mallet’s report on the 1857 Neapolitan earthquake (Mallet 1862)
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While the contribution to seismology, and the development of an approach which could be used by others, was the main aim of Mallet’s investigation, the report is full of important insights about the local construction techniques of the time and their failings. He makes the observation several times that where buildings are well-built, they were very little if at all damaged by the earthquake. The sketches and photos clearly demonstrate the principal mechanisms of failure of masonry structures, and the attempts to describe these in mathematical equations of equilibrium anticipate later important lines of enquiry about vulnerability and strengthening measures. So does his assembly of the available statistics on fatalities, which numbered more than 10,000. The concluding remarks in the report are striking:
All human difficulties to be dealt with must be understood: were understanding and skill applied to the future construction of houses and cities in Southern Italy, few if any human lives need ever again be lost by earthquakes; which must there recur in their times and seasons.
Unfortunately the reconstruction efforts following the 1857 earthquake substantially rebuilt the towns and villages of this area in the same manner as before; and when another major earthquake struck the same region in 1980, the destruction was just as severe and extremely similar in nature to that of 1857, and a further 3,000 deaths occurred. The town of Polla was affected by both earthquakes, and Figs. 1.5 and 1.6 show identical views of Polla following the two events, demonstrating the similarity of the damage, the former from the Mallet report, the later one taken by the author during a field reconnaissance there in 1981 (Spence et al. 1982).
Fig. 1.5
The damage to Polla, in Irpinia, in the 1857 earthquake (from frontispiece of Mallet 1862)
Fig. 1.6
Polla from the same location as Fig. 1.6 in 1981 after the Irpinia earthquake. Note similarity of building form and construction (Photo by author)
×
×
The methods proposed by Mallet did not find immediate scientific application, and his report (perhaps because of its severe criticism of Italian seismologists of the day) was little noticed in Italy until some 20 years after its publication (Ferrari 1987). Then first an Englishman (Johnson-Lavis), and subsequently the great seismologist Giuseppe Mercalli applied Mallet’s methods to the 1883 and 1885 earthquakes on the island of Ischia, then to the 1884 Andalusian earthquake and finally to the Ligurian earthquake of 1887, and in the process elaborated and extended them. The method was also taken up in India (Melville and Muir Wood 1987). However, within another 10 years instrumental seismology had arrived, and epicentres were in future to be located by instrumental means, a surer and less time-consuming approach. From the 1890s onwards, field investigations were concerned more with the determination of intensity, using the newly devised macroseismic intensity scale of Rossi and Forel (Melville and Muir Wood 1987). However, Omori (1908), after the 1908 Messina earthquake, used observations of overturned bodies to locate the point of origin of the event.
1.4 UNESCO Field Missions 1962–1980
Over period of nearly 20 years from 1962, UNESCO supported at least 23 post-earthquake reconnaissance missions. Nicholas Ambraseys was the leading figure in this programme: according to Michael Fournier d’Albe, then Head of the UNESCO Natural Hazards Programme, it was Ambraseys who was largely instrumental in persuading the UNESCO Secretariat in the early 1960s that “a useful purpose might be served by UNESCO sending international multidisciplinary teams to conduct field studies of damaging earthquakes as soon as possible after their occurrence”, and Ambraseys himself carried out the first of such studies of the Buyin-Zara earthquake in Iran in 1962. He subsequently participated in a further 12 of these studies; he gave a shape and a cohesion to the programme, and he made sure that the findings of the studies were properly recorded and made available to the governments of the countries concerned and to the wider research community.
An important element of the missions was their multi-disciplinarity: they all included seismologists, geologists and engineers. Many distinguished engineers and scientists participated in one or more of the missions, including J. Despeyroux, A Zatopek, A.A. Moinfar, S. Bubnov, T.P. Tassios and J.S Tchalenko. Indeed the 1964 Skopje Conference, at which the European Association for Earthquake Engineering was founded, took place as a direct result of the 1963 UNESCO mission to Skopje (Fig. 1.7).
Fig. 1.7
S.V. Medvedev, S. Bubnov and N.N. Ambraseys, founding members of EAEE, in Skopje in 1964
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A summary account of the programme was given by Ambraseys at the Intergovernmental Conference on the Assessment and Mitigation of Earthquake Risk organised by UNESCO in Paris in 1976. The general objective of the missions, simply stated, was “to investigate the cause and effects of such events for the purpose of adding to scientific and practical knowledge for the mitigation of their disastrous consequences” (Fournier-D’Albe 1986). More specifically Ambraseys (1976a) states that:
It is only through properly-run field studies that ground deformation or faulting associated with an earthquake can be discovered and studied and the bearing on local risk assessed. Existing building codes and regulations as well as the efficacy of their enforcement and implementation, can only be tested after an earthquake. It is only through well-designed and efficient field studies that the economic and social repercussions of an earthquake disaster can be identified so as to avoid undesirable results in future events.
The composition of the missions was dictated by the circumstances, whether the affected area was urban and small, rural and large, or not easily accessible. But a key aspect of the missions was that they were based on a small number of international experts, and drew in expertise from local organisations as far as possible. One further aim was to bring to the country and install a portable network of seismic stations, or at least a strong-motion accelerograph, although that proved possible in only a few cases. There was also a target that the mission should aim to arrive within 72 h of the earthquake’s occurrence, but this was never achieved, and the typical delay, mainly due to the waiting for permission from the host Government, was typically 3 weeks. However, once in place, the field studies typically lasted 3 or 4 weeks or more, much longer than is typical of many reconnaissance missions today.
Table 1.1 identifies the earthquakes for which the UNESCO Missions which took place between 1962 and 1980, and Figs. 1.10, 1.11 and 1.12 show the locations of the earthquakes studied. Reports on all these events were published by UNESCO. General features of all these reports are:
Information on the regional and local seismicity, including usually a detailed listing of all historical and instrumentally recorded damaging earthquakes.
An account of the actual earthquake and its overall effects, including foreshocks and aftershocks.
Details and analysis of any strong motion recordings available.
Detailed description of any surface faulting, and other geological or geotechnical features observed, with maps and photographs.
Description of typical forms of building construction found, and description, place by place of the extent and types of damage, with maps and photographs.
Description of notable civil engineering structures and any damage sustained.
Assessments of macroseismic intensity at the different locations visited, and where possible the preparation of preliminary intensity maps.
Recommendations for reconstruction.
Overall, this is an immense record of earthquake effects in more than 20 earthquake-prone locations, involving a huge individual research effort. Ambraseys said that he had himself spent, in total, more than 5 years of his life on such field investigations. A few of the more notable findings of specific missions are worth summarising.
Table 1.1
Summary of field missions, 1962–2013, undertaken by UNESCO, EERI, EEFIT, GTF, AFPS and JSCE
Year/Date
Earthquake
Country
Magnitude
EERI
EEFIT
German Taskforce
UNESCO
AFPS
JSCE
01/09/1962
Buyin-Zara
Iran
7.2
x
21/02/1963
Barce
Libya
5.6
x
26/07/1963
Skopje
Yugoslavia
6.0
x
20/03/1966
Toro
Uganda
6.4
x
19/08/1966
Varto
Turkey
6.8
x
17/10/1966
Lima
Peru
7.6
x
22/07/1967
Mudurnu
Turkey
7.1
x
29/07/1967
Caracas
Venezuela
6.5
x
10/12/1967
Koyna
India
6.5
x
01/08/1968
Luzon
Philippines
7.5
x
31/08/1968
Dasht-e-Bayaz
Iran
7.1
x
26/10/1969
Banja Luka
Yugoslavia
6.3
x
08/03/1970
Gediz
Turkey
7.1
x
07/04/1970
Luzon
Philippines
7.2
x
31/05/1970
Ancash-Chimbote
Peru
7.5
x
30/07/1970
Karnaveh
Iran
6.7
x
09/02/1971
San Fernando, California
USA
6.5
x
10/04/1972
Ghir
Iran
6.2
x
23/12/1972
Managua
Nicaragua
6.2
x
x
28/08/1973
Veracruz
Mexico
7.0
x
03/10/1974
Lima
Peru
7.2
x
28/12/1974
Pattan
Pakistan
6.4
x
01/08/1975
Oroville, California
USA
5.8
x
04/02/1976
Motaqua Fault
Guatemala
7.5
x
06/05/1976
Friuli
Italy
6.5
x
06/05/1976
Gemona
Italy
6.5
x
28/07/1976
Tangshan
China
7.8
x
17/08/1976
Mindanao
Philippines
7.9
x
04/03/1977
Vrancea
Romania
7.2
x
x
23/11/1977
Caucete and San Juan
Argentina
7.4
x
19/12/1977
Gisk
Iran
5.8
x
12/06/1978
Miyagi
Japan
7.5
x
20/06/1978
Salonica
Greece
6.4
x
29/11/1978
Oaxaca
Mexico
7.9
x
14/03/1979
Guerrero
Mexico
7.7
x
15/04/1979
Montenegro
Montenegro
7.2
x
15/10/1979
Imperial County, California
USA
6.4
x
24/01/1980
Greenville, California
USA
6.4
x
09/06/1980
Mexicali, Baja
Mexico
6.2
x
10/10/1980
El-Asnam
Algeria
7.3
x
x
08/11/1980
Offshore Trinidad, California
USA
7.0
x
23/11/1980
Campania-Basilicata
Italy
7.2
x
24/02/1981
Alcionides Isles
Greece
6.6, 6.3
x
09/01/1982
Miramichi, New Brunswick
Canada
5.7
x
19/06/1982
San Salvador
El Salvador
7.0
x
31/03/1983
Popayan
Colombia
5.5
x
02/05/1983
Coalinga, California
USA
6.5
x
26/05/1983
Nihan-Kai-Chubu
Japan
7.7
x
18/10/1983
Borah Peak, Idaho
USA
7.0
x
30/10/1983
Northeastern Turkey
Turkey
7.1
x
08/11/1983
Liege, Belgium
Belgium
5.0
x
16/11/1983
Kaoiki, Hawaii
USA
6.6
x
24/04/1984
Morgan Hill, California
USA
6.2
x
14/09/1984
Nagano-Ken Seibu
Japan
6.9
x
03/03/1985
Llolleo
Chile
7.5
x
x
19/09/1985
Guerrero-Michoacan (Mexico City)
Mexico
8.0
x
x
13/09/1986
Kalamata
Greece
6.2
x
10/10/1986
San Salvador
El Salvador
5.5
x
x
02/03/1987
Edgcumbe
New Zealand
6.3
x
01/10/1987
Whittier Narrows, California
USA
5.9
x
06/11/1988
Yunnan
China
7.6, 7.2
x
25/11/1988
Saguenay, Quebec
Canada
6.0
x
07/12/1988
Spitak
Armenia
6.8
x
x
17/10/1989
Loma Prieta, California
USA
6.9
x
x
x
27/12/1989
Newcastle, Australia
Australia
5.4
x
30/05/1990
Vrancea, Romania
Romania
7.0
x
16/07/1990
Luzon
Philippines
7.8
x
x
21/06/1990
Manjil
Iran
7.7
x
x
x
13/12/1990
Augusta, Sicily
Italy
5.6
x
22/04/1991
Valle de la Estrella
Costa Rica
7.7
x
20/10/1991
Garhwal
India
6.2
x
13/03/1992
Erzincan
Turkey
6.9
x
x
x
13/04/1992
Roermund
Netherlands
5.3
x
22/04/1992
Joshua Tree, California
USA
6.1
x
28/06/1992
Landers and Big Bear, California
USA
6.6
x
12/10/1992
Cairo
Egypt
5.9
x
25/03/1993
Scott Mills, Oregon
USA
5.6
x
12/07/1993
Hokkaido-Nansei-Oki
Japan
7.8
x
08/08/1993
South End of Island
Guam
8.1
x
20/09/1993
Klamath Falls, Oregon
USA
5.7
x
29/09/1993
Killari, Latur District, Maharashtra
India
6.2
x
x
17/01/1994
Northridge, California
USA
6.7
x
x
x
04/10/1994
Kuril Islands/Hokkaido Toho-oki
Japan
8.2
x
15/11/1994
Mindoro Island
Philippines
7.0
x
17/01/1995
Kobe
Japan
6.9
x
x
13/05/1995
Grevena (Central-North)
Greece
6.6
x
30/07/1995
Antofagasta, Chile
Chile
8.0
x
14/09/1995
Ometepec
Mexico
7.2
x
01/10/1995
Dinar
Turkey
6.0
x
07/10/1995
Sungaipenuh
Indonesia
7.0
x
09/10/1995
Manzanillo
Mexico
7.6
x
22/11/1995
Aqaba
Egypt
7.1
x
03/02/1996
Lijiang
China
6.2
x
17/02/1996
Irian Jaya Region
Indonesia
8.1
x
18/02/1996
St-Paul-de-Fenouillet
France
5.2
x
21/02/1996
Chimbote
Peru
7.4
x
12/11/1996
Nazca
Peru
7.5
x
10/05/1997
Ardekul
Iran
7.3
x
22/05/1997
Jabalpur
India
5.8
x
09/07/1997
Cariaco
Venezuela
6.9
x
x
x
26/09/1997
1997 Italy Series (Umbria-Marche)
Italy
5.5, 5.9, 5.3, 5.5, 5.7
x
x
27/06/1998
Adana-Ceyhan
Turkey
6.2
x
x
x
17/07/1998
Near North Coast
Papua New Guinea
7.0
x
25/01/1999
El Quindio
Colombia
6.2
x
x
x
x
29/03/1999
Chamoli
India
6.6
x
08/06/1999
Martinique
Martinique
5.6
x
15/06/1999
Tehuacan
Mexico
6.5
x
17/08/1999
Kocaeli
Turkey
7.6
x
x
x
31/08/1999
Izmit, Turkey
Turkey
5.1
x
x
07/09/1999
Athens
Greece
5.9
x
21/09/1999
Chi-Chi
Taiwan
7.7
x
x
x
x
12/11/1999
Duzce, Turkey
Turkey
7.2
x
13/01/2001
El Salvador
El Salvador
7.7
x
x
26/01/2001
Bhuj
India
7.7
x
x
x
x
28/02/2001
Nisqually, Washington
USA
6.8
x
23/06/2001
Southern Peru
Peru
8.4
x
x
03/02/2002
Sultandagi
Turkey
6.2
x
x
31/03/2002
Northeast Taiwan
Taiwan
7.1
x
22/06/2002
Ab garm-abhar-avaj-shirin su
Iran
6.5
x
31/10/2002
Molise
Italy
5.9
x
x
02/11/2002
Sumatra
Indonesia
7.4
x
03/11/2002
Denali, Alaska
USA
7.9
x
21/01/2003
Colima, Mexico
Mexico
7.6
x
01/05/2003
Bingöl
Turkey
6.4
x
x
21/05/2003
Boumerdes (Northern Algeria)
Algeria
6.8
x
x
x
x
26/05/2003
Minami Sanriku
Japan
7.0
x
26/07/2003
Northern Miyagi
Japan
5.1
x
22/09/2003
Puerto Plata
Dominican Republic
6.5
x
25/09/2003
Hokkaido
Japan
8.3
x
x
22/12/2003
San Simeon, California
USA
6.5
x
26/12/2003
Bam (Southeastern Iran)
Iran
6.6
x
x
x
24/02/2004
North Coast
Morocco
6.4
x
x
28/09/2004
Parkfield (Central California)
USA
6.0
x
23/10/2004
Niigata Ken Chuetsu
Japan
6.6
x
x
21/11/2004
Les Saintes
Guadeloupe
5.1
x
26/12/2004
Sumatra-Andaman Islands and Indian Ocean Tsunami
India, Indonesia, Maldives, Singapore, Sri Lanka, Thailand
9.0
x
x
x
20/03/2005
Kyushu
Japan
6.6
x
28/03/2005
Northern Sumatra
Indonesia
8.7
x
x
13/06/2005
Tarapaca
Chile
7.8
x
08/10/2005
Kashmir
India, Pakistan
7.6
x
x
x
x
08/01/2006
Kythira Island (Southwestern Greece)
Greece
6.9
x
26/05/2006
Java
Indonesia
6.3
x
x
x
17/07/2006
Java
Indonesia
7.7
x
26/12/2006
Taiwan
Taiwan
7.1
x
06/03/2007
Western Sumatra, Indonesia
Indonesia
6.4
x
x
25/03/2007
Noto Peninsula (offshore)
Japan
6.7
x
x
16/07/2007
Honshu (offshore)
Japan
6.6
x
x
x
15/08/2007
Near Central Coast, Peru
Peru
8.0
x
x
x
12/09/2007
Southern Sumatra
Indonesia
8.5
x
x
13/09/2007
Sumatra
Indonesia
7.9
x
14/11/2007
Antofagasta-Tocopilla, Chile
Chile
7.7
x
x
01/01/2008
Nura, Kygryzsta
Kygryzsta
5.6
x
12/05/2008
Wenchuan
China
7.9
x
x
x
08/06/2008
Offshore Greece
Greece
6.3
x
14/06/2008
Honshu
Japan
6.9
x
06/04/2009
L'Aquila, Italy
Italy
6.3
x
x
x
x
28/05/2009
Honduras (offshore)
Honduras
7.3
x
11/08/2009
Suraga Bay
Japan
6.5
x
02/09/2009
Java, Indonesia
Indonesia
7.0
x
29/09/2009
Samoan Islands
Samoa
8.0
x
x
30/09/2009
Padang, Indonesia
Indonesia
7.6
x
x
x
10/01/2010
Eureka
USA
6.5
x
12/01/2010
Haiti
Haiti
7.0
x
x
27/02/2010
Maule, Chile (offshore)
Chile
8.8
x
x
x
x
27/02/2010
Tori Shima
Japan
5.2
x
04/04/2010
Baja California, Mexico
Mexico, USA
7.2
x
04/09/2010
Canterbury, New Zealand
New Zealand
7.1
x
x
20/12/2010
Hosseinabad
Iran
6.5
x
22/02/2011
Christchurch, New Zealand
New Zealand
6.3
x
x
11/03/2011
Tohoku Japan
Japan
9.0
x
x
23/08/2011
Virginia
USA
5.8
x
18/09/2011
Sikkim
Bhutan, India, Nepal
6.9
x
23/10/2011
Eastern Turkey
Turkey
7.1
x
20/03/2012
Ometepec, Mexico
Mexico
7.4
x
11/08/2012
Varzaghan-Ahar, Iran
Iran
6.3, 6.4
x
07/11/2012
Champerico, Guatemala
Guatemala
7.4
x
11/11/2012
Shwebo, Myanmar
Myanmar
6.8
x
09/04/2013
Bushehr, Iran
Iran
6.4
x
20/04/2013
Lushan County, China
China
6.6
x
1.4.1 The M = 6.1 Skopje Earthquake of 26 July 1963
The earthquake, though not of great magnitude, was of shallow depth, and had its epicentre close to or within the city. The report concentrated on damage within Skopje itself, a city which had grown very rapidly from a population of 47,000 in 1947 to 220,000 in 1962. Damage was in some areas very severe, but much of the city’s infrastructure was left intact or repairable; the spatial damage distribution was difficult to understand. Varying soil conditions, marked variations in the standards of construction, particularly in reinforced concrete structures, and the effect of the 1962 Vardar floods on basements and subsoil conditions were all thought to have played a part. Flexible structures were found to have behaved far better than rigid ones (UNESCO 1963).
1.4.2 The M = 6.8 Varto-Üstükran Earthquake of 19 August 1966
Damage was over a wide, largely rural, area of Eastern Turkey, and many houses of traditional adobe or stone masonry construction collapsed. Some houses used reinforced concrete, but construction standards were very poor. It was impossible to assess macroseismic intensity above MMI VII + in rural areas, because in many places all buildings collapsed at this intensity; damage from a series of foreshocks in the months before the August earthquake probably contributed to this. The report concluded that, for this reason, past assessments of intensity in developing countries may have been systematically overestimated (Ambraseys and Zatopek 1967).
1.4.3 The M = 7.1 Mudurnu Valley Earthquake of 22 July 1967
This earthquake, on a section of the North Anatolian Fault with many previous recorded events, caused more than 80 km of surface rupture. The fault displacement was traced along the whole of this rupture length, with a maximum right lateral displacement of 1.9 and 1.2 m vertical; observations on power lines suggested that there was considerable additional displacement away from the immediate surface rupture. Damage was very severe over a wide area, but damage in the immediate vicinity of the fault break was no higher than that at distances as much as 10 km from the fault. As for the Varto earthquake, it was impossible to assess intensities above MMI VII because almost all adobe construction collapsed. There was a very large difference between the performance of adobe and timber-frame buildings, which survived well. There were significant ground displacements and associated liquefaction in and around Sapanca Lake (an observation which was to be repeated in the 1999 Kocaeli and Duzce earthquakes, which also affected this part of the fault zone) (Ambraseys et al. 1968).
1.4.4 The M = 6.4 Pattan Earthquake of 28 December 1974
The earthquake affected a mountainous region of Northern Pakistan characterised by steep slopes and deep valleys, with a relatively small seasonally migrant agricultural population. The focal depth, as deduced from the seismic array at the Tarbela Dam 130 km south, was relatively shallow, about 5 km, and the directionality of movement was in accordance with expected movement on the Himalayan thrust; however there was no observed surface faulting. Widespread rockfalls damaged roads; and the earthquake occurred in winter, making access to many of the affected places difficult. Nevertheless the UNESCO team were able to visit most of the worst damaged settlements, often on foot, and record the damage distribution. Stone masonry is a common material of construction in the area, and marked differences in level of damage were noted according to the form of construction. In many cases the roofs (flat packed earth on timber rafters), were supported independently of the timber-laced rubble-filled walls on separate timber columns (Fig. 1.8); in other cases the roofs were directly supported on the walls. The houses which had bearing walls were found to have suffered severely from the earthquake, but those with independent columns much less. (This observation was to be followed up in the 1980 International Karakoram Project, Spence et al. 1983). There were very few modern structures in the area. Brick masonry buildings with good quality mortar were little damaged, but others were damaged severely. Bridges generally survived intact, but the Karakoram Highway was seriously affected by rockfalls in many places (Ambraseys et al. 1975).
Fig. 1.8
Stone masonry buildings with roofs supported on timber columns independently of the walls, from UNESCO mission to 1974 Pattan earthquake (Ambraseys et al. 1975)
×
1.4.5 The M = 6.3 Gemona di Friuli Earthquake of 6 May 1976
The earthquake was the first visited by a UNESCO team to occur in an area with a large number of buildings of historical importance. The main objective of this mission was to study damage to structures, rather than investigate the geological and seismological aspects. The team accordingly consisted of two architects and an engineer (Ambraseys), and the report divides into three separate parts. The report notes the unusually large number of large aftershocks, associated with earthquakes in this region. The damage caused by this repeated activity compounded that resulting from the age and poor quality of much construction. Construction methods typical of the Friuli region of Italy are described in detail, and the many weaknesses in the stone masonry leading to damage and collapse are described; these were further compounded by improper repair, war damage and previous earthquakes; it is noted, though, that many houses were saved from collapse by the use of tie-rods in masonry walls which held walls together. A detailed listing of the historic churches and palazzi damaged by the earthquake is given, covering a very wide area but with a particular concentration in the historic towns of Gemona and Venzone. A section discusses the loss of life and injuries, and its demographic distribution, and analyses possible reasons for higher casualties among the young adult population in the older town centres, probably the first time this issue was considered in a field mission report (Ambraseys 1976b).
1.4.6 The M = 7.2 Romania Earthquake of 4 March 1977
This report, like that of Friuli, is also a compilation of separate reports, that of Ambraseys dealing with the earthquake and its principal effects, and that of Despeyroux dealing with the behaviour of buildings. The earthquake was deep (110 km); it occurred in the same area, with a very similar magnitude and depth as a previous one in 1940 (and, indeed a later one in 1990). Both earthquakes caused moderate damage over a wide area (around 80,000 km2), with a particular concentration of damage in Bucharest about 200 km away from the focus. Much of the damage was sustained by older reinforced concrete frame buildings which had either been damaged in 1940 or built without provision for earthquake loading (Fig. 1.9). By contrast, small brick bearing wall structures suffered relatively minor damage. The recording of a strong motion accelerograph from the Building Research Institute in Bucharest was analysed, and the response spectrum approximately extracted, showing a peak between 1.5 and 2 s. The concentration of damage in 6–12 storey RC frame buildings (with fundamental periods of 0.7–1.6 s (the ascending branch of the response spectrum) is thus explained. Over the whole affected area, intensity assessment was made very difficult because of the lack of damage caused by high-frequency ground motion. Earlier attempts to provide a microzonation of Romania and Bucharest are shown to have been ineffective for this event: the report notes that there was “not the slightest similarity in pattern between the predicted and observed damage pattern”. The importance of reconsidering the design codes to be able to deal with both long–period motions from distant earthquakes and local, shallow earthquakes is emphasised (Ambraseys and Despeyroux 1978).
Fig. 1.9
Damage to older reinforced concrete buildings in Bucharest in the 1977 Romania earthquake, recorded by the UNESCO mission (Ambraseys and Despeyroux 1978)
×
The 1980 El Asnam Mission was the last such UNESCO mission. While it lasted, the UNESCO programme made vital contributions to the understanding of earthquake effects across a wide area of the world. Fault systems were mapped, ground motion and response spectra and their distribution was reported and analysed where possible, the distribution of damage across the affected zone was explored, the effects of subsoil conditions investigated, and the performance of a variety of types of building, including historical structures in several cases, was also investigated. One particular aspect of this was demonstrating the relative performance of different traditional building types in a way which is today less common, as field missions nowadays concentrate more on engineered and modern structures. The style and contents of the UNESCO Reports was to become a template for those of later field missions.
But the inherent inter-disciplinarity of the UNESCO Missions was perhaps difficult to keep going as the field investigation techniques of the different disciplines matured and it also became more common to involve research students in the data collection. And as Fournier-D’Albe (1986) states in the Foreword to the compilation of field reports, the administrative obstacles that such UN-sponsored international missions had to overcome were steadily increasing. From 1980 onwards earthquake engineering reconnaissance missions organised by national societies, and supported by research councils and by industry began to become more common, while earth scientists have tended to conduct separate studies with different itineraries and timescales.
1.5 EERI Learning from Earthquakes Programme (1972–2014)
The Earthquake Engineering Research Institute, based in Oakland California, was founded in 1949, and has conducted post-earthquake field investigations, both of US and non-US earthquakes from its inception. However, until 1971 these missions were ad-hoc responses to the events, largely focussed on investigating damage to buildings. The 1971 San Fernando earthquake was the stimulus to establishing EERI’s Learning from Earthquakes (LFE) programme; it became clear from that event that advance planning and coordination would have been beneficial to achieve the maximum benefit in understanding the damage, and ensuring that all aspects of the event were examined, and avoiding the tendency of individual surveys to duplicate each others’ investigations. The LFE programme was formalised in 1973, with three principal activities: conducting field investigations; developing guidelines for conducting post-earthquake investigations that enable consistent data to be collected; and disseminating the lessons learned (EERI 1986, 1995a). For many years funding for the LFE programme has been provided by the US National Science Foundation.
Today, after mounting investigations of nearly 300 events, EERI has developed a highly professional approach to the mounting and management of field missions, and can claim to be the world’s leading earthquake field investigation organisation. With a large worldwide individual membership, EERI is in many respects an international organisation with a global outreach. As well as documenting each separate mission, EERI has also documented the overall learning from its field missions in a number of different publications (EERI 1986, 2004).
EERI is notified on a 24-h basis of all global earthquakes likely to have been damaging by the National Earthquake Information Service of USGS; the Executive Committee then has responsibility for deciding which earthquakes EERI will investigate. The level of response is determined by the location and extent of damage. In general terms for small earthquakes in the USA or for moderate earthquake abroad, EERI identifies members in the area who can be asked to conduct a short investigation and produce a brief report for the EERI newsletter. For earthquakes outside the USA which “hold potentially significant lessons for US practice”, a multidisciplinary reconnaissance team of 4–8 members is sent into the field for typically 1 week or more; EERI members from the affected country are often members, sometimes the leaders, of such reconnaissance teams. The aims of such reconnaissance teams (EERI 1995a) are:
1.
To collect the available perishable data in an effort to learn as much as possible about the nature and extent of damage and identify possible gaps in existing research or in the practical application of scientific, engineering and policy knowledge, and
2.
To make recommendations regarding the need for further research and suggest possible foci.
For significant earthquakes in the USA, similar reconnaissance teams may be mounted, but for US events EERI also works closely with local universities or companies which are mounting their own investigations to ensure that all available observations are assembled and reported.
Aspects normally investigated by EERI post-earthquake reconnaissance missions are very broad, but generally include the following:
Geosciences
Geotechnical engineering
Engineered buildings
Industrial facilities
Lifelines and transportation structures
Architectural and non-structural elements
Emergency management and response
Societal impacts
Urban planning and public policy implications
Each of these topics normally constitutes a chapter of the final report. Where appropriate a chapter on tsunami impacts may also be included. The level of geoscience investigation varies: but is usually primarily associated with the level of ground shaking and its distribution, with less attention to the investigation of the underlying faulting as was attempted by the earlier UNESCO mission teams.
An important feature of EERI’s programme are the detailed procedures laid down for the recruitment, briefing, activity in the field, and post-event debriefing of the reconnaissance team members, all of whom are volunteers. A balanced team membership whose members are experienced and capable to deal with all the above aspects is selected. For non-US earthquakes a team leader and team members able to speak the local language are sought. Advice is also given on dealing with the media, and the responsibility of all team members for contributing to the final reports is emphasised (EERI 1995a).
The total number of field missions of all types conducted by EERI since the 1971 San Fernando earthquake is 290, of which 138 have led to Reconnaissance Team Reports or Earthquake Spectra articles. Of these only 34 were in the USA, Canada or Mexico, the remaining 104 were elsewhere in the world. On average there have been about four such missions per year since 1990. Table 1.1 lists all of the 138 events reported in detail, and their locations are shown on the maps, Figs. 1.10, 1.11 and 1.12.
Fig. 1.10
Locations of all field investigations by different reconnaissance teams 1962–2013
Detail of Fig. 1.10 for USA and Central America region
×
×
×
The cumulative learning from all of these field missions is immense. An early review was made in the publication Reducing Earthquake Hazards (EERI 1986), and learning was more briefly reviewed in Learning from Earthquakes (EERI 2004). A selection of some of the most important contributions noted by these publications, many of which are now widely accepted generalisations, includes the following.
1.5.1 Contributions to Structural Engineering
It has consistently been found that well-designed, well detailed and well-constructed buildings resist earthquake-induced forces without excessive damage, though designing to code does not necessarily protect against severe damage; damage and collapse of buildings can often be attributed to poor construction practice and lack of quality control. Detailing for ductility and redundancy provide safety against collapse: a complete load path designed for seismic forces must be provided. The stiffness of the lateral load resisting system has a major effect on both structural and non-structural damage. Properly designed horizontal diaphragms are essential. Irregularities in both plan and elevation can have a very significant effect on earthquake performance, especially soft stories. Inadequate distance between buildings can result in pounding damage. Stiff elements not considered in the design can strongly affect the seismic response of a building (Fig. 1.13).
Fig. 1.13
Damage to precast concrete garage structure in the 1994 Northridge earthquake from the EERI photographic dataset for that earthquake (EERI 1995a)
×
The relative performance of structures with different load-resisting systems has shown that unreinforced masonry buildings have performed poorly, though better if strengthened with steel ties; by contrast reinforced and confined masonry buildings have performed well. Steel frame buildings have generally performed well, though investigations following the 1994 Northridge and 1995 Kobe earthquakes found unexpected levels of damage to welded connections. Performance of precast and pre-stressed concrete buildings depend critically on the connection of the elements; exterior panels and parapets need strong anchoring to protect life safety. Though timber frame structures often perform comparatively well, various recent forms of wood frame construction has been found to have serious weaknesses. Reinforced concrete frame buildings often demonstrate similar weaknesses, including the roles of a soft storey, nonductile elements, and irregularities in contributing to damage or collapse.
The importance of such observations consists not only in their occurrence and reporting in one earthquake, but in the repetition of the same observation in many earthquakes in different regions with differing patterns of ground motion, in building stocks designed to different codes and built according to differing local practices.
These and other observations derived from field studies have led, often through subsequent research programmes (such as that of Arnold and Reitherman 1982), to the progressive development of the building codes for earthquake-resistant construction in the USA, from ATC3-06 (ATC 1978) through to the current version of the International Building Code (International Code Council 2012). The US codes, in turn, have influenced earthquake construction codes in other countries of the world. Thus a direct link can be traced between the structural engineering findings of these EERI Field Reconnaissance Missions and today’s best practice in the structural design of buildings worldwide. Field mission experience has also led to the definition of a small number of Model Building Types (FEMA 2003; Jaiswal et al. 2011) used in loss estimation studies, and to the development of standards for the evaluation of existing buildings to assess whether they should be strengthened (ASCE 2003). Field investigations have also helped gain acceptance for new technologies such as seismic isolation and semi-active control (Booth, pers comm).
1.5.2 Contributions to Site Effects and Geotechnical Engineering
Field investigations of the distribution of damage, coupled with the increasing availability of strong ground motion recordings of the main shock and aftershocks, has led to a better understanding of the role played by site conditions on the amplification of ground motion and the types and distribution of damage to structures. Prior to 1999 there were only eight strong ground motion recordings worldwide within 20 km of the fault for earthquakes greater than M = 7 (EERI 2004). In the last 15 years this situation has been transformed by the much wider availability of such records which, coupled with field observation of damage, has enabled a much better understanding to be gained of the role played by soil amplification, topographical effects, location in relation to the fault, and the nature of the ground motion, on the damage to structures caused by earthquakes.
As a result of this, it is now widely recognised that no single parameter of ground motion can be used to define the damage capability of strong ground motion, and that features such as fault-rupture type, duration, frequency content, and the ratio of vertical to horizontal ground motion amplitudes have to be considered in different ways for different classes of structures. In some especially well-instrumented events such as 1994 Northridge, effects of ground motion directivity and of high vertical acceleration on damage distributions have been observed. For different regions, ground motion prediction equations have been developed through which it is possible to estimate the ground motion for locations where it has not been measured directly.
Liquefaction effects have been observed in reconnaissance missions following a number of earthquakes, notably 1989 Loma Prieta, 1995 Kobe, 1999 Kocaeli , 2004 Niigata 2010 Haiti and 2011 Christchurch events, which have enabled an extensive database of liquefaction effects to buildings, bridges, port structures and pipelines to be assembled, enabling improvements in the design of such structures in soils with a liquefaction potential. Field missions have enabled similar advances in understanding of the deformations caused by the displacement at surface fault ruptures and by landslides.
1.5.3 Contributions to Lifeline Engineering
Investigations into the performance of lifelines have been a crucial aspect of EERI reconnaissance missions. Bridges and highway structures, gas and water pipelines, and electrical power generation and transmission systems all suffered damage in recent earthquakes. The data assembled by field missions has included damage, lost service and needed repair. This has identified both systems that have performed well and those that failed; and has resulted in numerous changes to design practices including better characterisation of ground motion, better specification of materials, anchorage details and welding practices. Damage to the power supply system in the 1999 Taiwan earthquake demonstrated the importance of building redundancy into lifeline systems.
1.5.4 Contributions to Social Science (and Urban Planning)
Since 1977 social scientists have regularly contributed to field reconnaissance missions, studying aspects of mitigation, response and preparedness, and more recently post-earthquake recovery. These observations have been used in the design of disaster plans for areas of the US which have not experienced an earthquake. From such studies, conducted in many different societies, certain general conclusions have been reached. It is now widely understood that that the most effective search and rescue activity is neighbourhood-based, involving informal groups of individuals who are on the scene because they live or work there; this has been used in the US to develop training programmes for neighbourhood groups. It is also understood that self-protective practices applicable for well-designed structures do not work in poorly built or weak masonry structures. Observations of emergency response procedures adopted in different situations have demonstrated a need for a more integrated approach to building design, land-use planning and emergency response in many seismic hazard areas. Experience in communities affected by tsunamis has provided important lessons in the best way to manage the distribution of warnings to potentially affected communities. Strategies for providing temporary shelter in different societies have been observed and their effectiveness reviewed. More recent field missions have revisited areas affected by earthquakes after a lapse of some months or years, and a database is being assembled of longer-term recovery experiences, which will provide data on the relative success of, for example, centralised or decentralised approaches to recovery. In recent events, the availability of rapid post-event damage estimation (e.g. using the USGS PAGER, or QLARM approach, Jaiswal et al. 2011; Trendafilowski et al. 2011) has enabled an early assessment of recovery needs. The impact of such early warnings has been assessed in recent events.
1.5.5 Use of Information Technology
EERI has been involved in pioneering the use and development of new information technology tools for post-earthquake reconnaissance. High-resolution satellite imagery has now been available for more than 10 years, and was first used to examine damage after the 2001 Gujarat earthquake in India (Saito et al. 2004). More recently, the satellite image providers have been able to rapidly make available before-event and after-event images of the most badly affected areas at less than 1 m resolution, and these have been used to guide reconnaissance missions in the field. Field investigations (2003 Bam, 2010 Haiti) have experimented with the use of VIEWS, a satellite linked video camera for recording damage, enabling a large increase in the speed of capturing building-by-building damage data in ground surveys. In recent earthquakes EERI has, in conjunction with ImageCat, deployed the GEOCAN network, a method of obtaining a rapid building-by-building damage assessment directly from satellite imagery using crowd sourcing (this technology is further discussed in Sect. 1.7). After recent events EERI has established a web-based data assembly and dissemination tool, called the Virtual Clearinghouse, on the EERI website. This enables the field team, the researcher community and EERI to upload data and communicate rapidly. The Virtual Clearinghouse has been mounted for 12 events since 2009.
1.6 EEFIT (1982–2014)
The UK-based Earthquake Engineering Field Investigation Team (EEFIT) was founded in 1982. Its direct origin was a field investigation of the 1980 Irpinia Earthquake in Southern Italy by the author with several UK colleagues (Spence et al. 1982). Because of logistical difficulties, this field investigation did not take place until four months after the earthquake, and it was realised that for field missions to be most effective they should occur earlier; for this to be possible, a team should be ready to mobilise at short notice, with procedures and funding sources in place beforehand. In 1982 EEFIT was formed as “a UK-based group of engineers, architects and scientists who seek to collaborate with colleagues in earthquake-prone countries in the task of improving the seismic resistance of both traditional and engineered structures”. It was supported by both the Institution of Civil Engineers though SECED (the British national section of IAEE) and the Institution of Structural Engineers (IStructE). From the outset EEFIT was envisaged as a collaboration between academic institutions and the practising engineering profession.
EEFIT exists solely to facilitate the formation of investigation teams which are able to undertake, at short notice, field studies following major damaging earthquakes and to disseminate the findings to engineers, academics, researchers and extent the general public. The objectives are to collect data and make observations leading to improvements in design methods and techniques for strengthening and retrofit, and where appropriate to initiate longer-term studies. Field training for engineers involved in earthquake-resistant design practice and research is also one of its key objectives. Recently EEFIT has extended its activities by conducting two longitudinal studies, one to L’Aquila (Rossetto et al. 2014) and one to Tohoku, Japan; the objectives of these were to better understand the recovery process and how engineers can contribute to this. The observations and findings from these missions are published in detailed reports and usually include sections on:
Mission methodology
The earthquake affected region
Seismological aspects
Types of damage, including distribution and extent, on both engineered and non-engineered structures
For any major reported earthquake, the EEFIT management committee decides whether the event might merit an investigation; if so, EEFIT members are invited to express an interest in joining a mission; the management committee then decides whether a mission is justified, who should be invited to participate and who should be the team leader. The team leader, a person with experience of previous missions and if possible also with knowledge of the country affected, organises the logistics of the mission, including making local contacts and obtaining any permissions needed. Team members are briefed by the team leader including any necessary risk assessments, and asked to sign a form committing them, among other things, to contribute to the final report. Since the late 1980s IStructE has provided the secretarial support for EEFIT. The relatively small recurrent central office costs of running EEFIT are met by IStructE, as well as membership subscriptions and corporate sponsorship. The time and mission expenses of practising engineers are provided by their employers, while the expenses of academic participants is met by specific grants from the UK Engineering and Physical Sciences Research Council, using an accelerated application procedure. Since 2010 EPSRC has provided funding for a 5-year programme of work, which has ensured that reconnaissance missions can continue to be supported, and has enabled follow-up missions to take place (Rossetto et al. 2014; Booth et al. 2011a).
Between 1982 and 2014 EEFIT reconnaissance team have visited and produced reports on 29 separate earthquakes, including most of the significant events of the period, with two of these (2009 L’Aquila and 2011 Tohoku) having had follow-up missions. A list of these events is shown in Table 1.1, and the locations are shown in Figs. 1.10, 1.11 and 1.12. Eight of these events have been in the wider European area (in countries with EAEE membership, Fig. 1.11). Collaboration with other national teams has been an important feature of these missions where possible, and EEFIT has collaborated with teams from France, Italy, Turkey, USA, Chile, Peru and New Zealand.
The findings of EEFIT reports echo, in many respects, those of the EERI missions listed earlier. An important aspect of EEFIT’s mission is in the training of younger engineers and scientists, and this has been achieved by the participation of over 100 engineers and scientists in EEFIT missions, more or less equally divided between industry and academia. EEFIT members have been involved in the development of Eurocode 8, now governing the design of structures in most EU countries, helping to bring field observations into new code provisions. As in the USA, field mission findings have been the basis for a number of important subsequent research programmes (Booth et al. 2011a) including:
Development of guidelines for the post-earthquake investigation of historical structures and non-engineered buildings Fig. 1.14, and approaches for the repair and strengthening of masonry structures (Hughes and Lubkowski 1999; Patel et al. 2001).
Fig. 1.14
Damage to the Basilica of S. Francisco at Assisi in the 1997 Umbria-Marche Earthquake: investigation of performance of historical structures has been a regular feature of EEFIT missions (Spence 1998)
×
Development of vulnerability functions for masonry structures and historic centres (D’Ayala 2013) and the need for code provisions for vernacular structures (D’Ayala and Benzoni 2012); these are further discussed in Sect. 1.8.
The development of databases of earthquake damage data: in recent years these have been web-based searchable databases, which enable cross-event comparisons to be made, such as CEQID (Spence et al. 2011) and GEMECD (So et al. 2012); these are further discussed in Sect. 1.8.
Soil amplification and other effects following the Mexico earthquake of 1985 (Steedman et al. 1986; Heidebrecht et al. 1990).
Seismic hazard and risk in areas of low seismicity (Chandler et al. 1991; Pappin et al. 1994).
Modelling of tsunami impacts on structures (Allsop et al. 2008).
Mitigation of liquefaction effects on foundations (Brennan and Madabhushi 2002).
Performance of earth dams in earthquakes (Madabhushi and Haigh 2005).
Understanding human casualties associated with building damage in earthquakes (So et al. 2008); this is further discussed in Sect. 1.8.
Assessment and validation of damage estimates from satellite and aerial images (Booth et al. 2011b; Foulser-Piggott et al. 2014); this work is further discussed in Sect. 1.8.
Relationships between ground motions and observed damage (Goda et al. 2013)
These research programmes have in their turn, affected both engineering practice and design regulations in the country affected and elsewhere. Of equal importance, perhaps, have been the establishment of lasting collaborations with colleagues and research teams in the affected countries, which, particularly in the EU countries, have led to UK involvement in long-term funded collaborations such as RiskUE (2001–2004), LessLoss (2004–2008) and PERPETUATE (2009–2012).
1.7 Other Post-Earthquake Field Reconnaissance Teams
This discussion has emphasised the UNESCO, EERI and EEFIT missions primarily because these were deliberately set up to be international in scope, and also because these are the best documented archives of earthquake damage descriptions available in the English language. But post-earthquake reconnaissance missions and associated reports on damage have been made by many other organisations and by individual efforts; there are national teams in many countries set up to undertake post-earthquake reconnaissance, notably in Japan, France, Germany, Italy, Greece, Turkey and China. Many university groups have fielded reconnaissance missions to study particular aspects of earthquakes; consultancy, insurance and modelling companies have fielded their own reconnaissance missions to obtain data for their own purposes, some of which has been published; and the literature can yield many thousands of individual observations of earthquake damage, which can be of great value, particularly eyewitness accounts by acute observers such as that of Rev Charles Davy documenting his experiences of the 1755 Lisbon earthquake (Davy 1755), Swedish doctor Axel Munthe describing his experiences in the ruins of Messina in 1908 (Munthe 1929), or writer Jack London’s account of the 1906 San Francisco (London 1906). To conclude this section, the aims and achievements of three further teams with international scope will be briefly summarised.
1.7.1 Japanese Society for Civil Engineering (JSCE)
Since 1993 JSCE has had a programme of sending field investigation teams to all major events both in Japan and overseas. Multidisciplinary teams have investigated strong motion, engineering and post-disaster response aspects of the events, and reports from 1996 to 2010 are available on the JSCE website (www.jsce.or.jp/library/eq_repo/index.html). The 38 reports covering this period are listed in Table 1.1, and their locations are shown in Figs. 1.10, 1.11 and 1.12. Ten of these were in Japan, 12 of the others elsewhere in Asia. The joint JSCE team investigation with the Architectural Institute of Japan and the Japan Geotechnical Society after the 1999 Kocaeli earthquake in Turkey, involving a joint team of Japanese and Turkish scientists, was perhaps the most intensive investigation of that event, including a detailed building by building survey of more than 2000 buildings in the heavily damaged town of Gölcük (AIJ 2000).
1.7.2 German Task Force (GTF)
The German Task Force for Earthquakes is a multidisciplinary response team which was founded in 1993; it consists of scientists from geosciences, structural engineering, sociologists and rescue specialists. It has three subsections: geology and geophysics (the main core of the taskforce), building and underground studies, and economic and societal affairs (Eggert et al. 2014). An important aspect of GTF missions is the deployment of a network of strong motion instruments in the affected area, sometimes in collaboration with other scientific teams. Since 1993 GTF participated in 22 national and international rapid response actions after earthquakes. Eleven of these are listed in Eggert et al. (2014) of which seven had structural engineering participation in the team. Dates and locations of these are listed in Table 1.1 and shown in Figs. 1.10, 1.11 and 1.12. The seismological data acquired is stored within the GEOFON data archive at GFZ Potsdam (http://geofon.gfz-postadam.de/waveform/). The building-related reconnaissance mission reports are available online at http://www.edac.biz/field_missions/german_taskforce_for_earthquakes.html?L=1
1.7.3 AFPS (Association Francaise du Genie Parasismique)
AFPS is a French society set up in 1983 on the initiative of Jean Despeyroux to promote the study of earthquakes and their consequences, and to promote measures to mitigate their effects and to protect human life. One of its central activities has been to send field missions to areas affected by earthquakes, especially, but not exclusively in French speaking countries. The first of these field missions was to the 1988 Spitak Armenia earthquake, and the AFPS website lists reports on 22 earthquakes since that time which have been visited by AFPS teams. These are listed in Table 1.1, and shown in Figs. 1.10, 1.11 and 1.12. Reports on all these events are available through the AFPS website (www.afps-seisme.org). The 92-page Report on the 2003 Boumerdes Algeria earthquake (Mouroux 2003) is probably the most detailed available record of that event.
1.8 Some Contributions of Post-Earthquake Field Missions to Earthquake Engineering
1.8.1 Understanding Performance of Non-engineered Structures
From Mallet onwards, field reconnaissance missions have frequently found that a large proportion of the damage has been suffered by so-called “non-engineered” structures, mostly ordinary domestic buildings built according to the local vernacular, but also larger public buildings, churches, mosques etc which may be of historical importance. Sections discussing the performance of non-engineered or vernacular structures often form a part of the field reconnaissance reports, especially those of UNESCO and EEFIT, both of which organisations specifically set out to record such damage.
Performance of non-engineered and/or historical buildings are discussed in detail for example in the UNESCO reports on the 1966 Varto, 1967 Mudurnu (Ambraseys et al. 1968), 1974 Pattan (Ambraseys et al. 1975) and 1976 Friuli earthquake and in the EEFIT reports on the 1990 Romania, (Pomonis 1990), 1992 Erzincan (Williams 1992), 1997 Umbria-Marche (Spence 1998) and 2010 Maule, Chile (Lubkowski 2010) earthquakes. Additionally historical structures formed an important part also of the EEFIT report on the 2009 L’Aquila earthquake (Rossetto 2009). Other field investigators, notably Langenbach (2000), have focused exclusively on investigation of vernacular structures. In the 1997 Umbria-Marche and 2010 Maule earthquake it was possible to observe the performance of buildings which had been strengthened by relatively recent interventions specifically to improve their earthquake resistance (Fig. 1.15).
Fig. 1.15
Investigation of the performance of strengthened historical structures formed part of the EEFIT reconnaissance following the 2010 Maule Chile earthquake (Lubkowski 2010)
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The conclusions of such investigations reveal much of interest about the comparative performance of different forms of traditional construction, and also about the performance of traditional structures by comparison with more recent engineered ones. In a variety of field reports, it has been observed that lightweight structures, using timber frames, have had a surprisingly good performance. Local traditions such as quincha and bahareque in Central and South America, himis and baghdadi in Turkey, and also masonry-infilled timber frame construction dhajji diwari in Kashmir performed comparatively well (Spence 2007) (Fig. 1.16). In Pakistan, as noted earlier, the UNESCO mission following the 1974 Pattan earthquake observed much better performance in stone masonry buildings in which the flat roof was independently supported on timber columns than in those buildings in which the roof was directly supported by the walls (Ambraseys et al. 1974) (Fig. 1.8). However, conversely, many local traditional building types, especially those using field stone masonry or earthen construction, performed very poorly, and uniformly collapsed at relatively low levels of ground motion. Buildings with heavy mud roofs, or vaulted roofs, have been found to perform very poorly. But also certain forms of timber-frame structure, such as the traditional heavy-roof construction in Kobe, often performed badly (Chandler and Pomonis 1995).
Fig. 1.16
Dhajji Diwari construction in Kashmir, found to have performed much better than more recent forms of construction in Indian Kashmir following the 2005 Kashmir earthquake (Langenbach 2000)
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For historical structures, several studies have concentrated on identifying the particular mechanisms of damage using methods proposed by Lagomarsino et al. 1997. Common mechanisms of damage found in the 1997 Umbria-Marche, 2009 L’Aquila and 2010 Maule earthquakes include shear cracks in walls, separation of walls at corners, overturning of facades, collapse of masonry arches and vaults, and separation of roof trusses from supporting walls. Strengthening interventions intended to improve performance seem in some cases to have contributed to the failure, as for example in the case of the Basilica of S Francesco at Assisi in 1997 (Spence 1998), or more recent evidence of failure of several churches in L’Aquila (Cimellaro et al. 2011) and Maule Chile (D’Ayala and Benzoni 2012).
It is worth considering what have been the benefits of such field investigations for earthquake engineering, given that these are structure types which are not designed by engineers. One benefit is in loss modelling: the accumulation of data on damage enables us to model the performance of these building types, some of which continue to be built in large numbers, and to estimate, for future events, what damage and attendant casualties will occur given any particular ground motion scenario. A second, more positive benefit is that the observation of relative damage enables good practice to be identified. Many “building for safety” programmes have been set up, in recent years (ASAG 1996; Schilderman 2004), which have had the aim of bringing good earthquake resistant design practice to the construction of small buildings in rural areas through builder training, for example in the application of timber or reinforced concrete ring-beams to masonry structures, improving masonry bonding, promoting improved quincha construction etc., and nowadays using grouting or reinforced masonry (NSET 2005). There have been to date still relatively few such programmes and most have been confined to areas which are in the process of reconstruction following an earthquake; but they will be important as long as housing in earthquake risk areas continues to be owner-built rather than engineered. And this will continue to be an important role, currently rather overlooked, for the engineering profession.
A further benefit is in the application to the protection of historical monuments. In countries such as Italy and Greece, protection of the national heritage of historical monuments has a high priority, and a huge number of valuable monuments are at risk from earthquakes and other hazards. The observation of damage from past earthquakes has enabled a number of common mechanisms of damage to be classified (Lagomarsino et al. 1997; D’Ayala 2013); and this enabled not only modelling of expected damage from future earthquakes, but also has led to development of techniques for improving the earthquake-resistance of such structures with minimal impact on the integrity of the ancient fabric of the monument. Such work has been the core of two recently completed EU-funded research programmes PERPETUATE (www.perpetuate.eu) and NIKER (www.niker.eu) (D’Ayala and Paganoni 2014). Thus earthquake field reconnaissance missions have fed directly and indirectly into important earthquake engineering work in the protection of Europe’s historic monuments.
1.8.2 Understanding Human Casualties
Understanding of the direct and indirect causes of casualties (deaths and injuries) in earthquakes is of importance to help formulate appropriate mitigation strategies, to develop public advice for self-protection, for the planning of search and rescue, and also to enable loss modelling to include estimates of potential numbers of people killed and injured in future earthquake scenarios. Most of what is currently understood about human casualties is derived from post-earthquake field investigations: although immediate post-earthquake reconnaissance missions have contributed important data on the most vulnerable locations and building types, much of the detailed understanding has come from a relatively small number of detailed surveys of earthquake survivors which have taken place in the months following earthquakes. The factors influencing the likely numbers of casualties in any future event are numerous. An epidemiological summary of the available studies by Petal (2011) has identified 5 classes of variables affecting casualty rates:
Building (construction type, level and type of damage)
Mitigation (household preparedness and first response skills)
Response (speed and effectiveness of search and rescue)
Alexander examined the casualty data following the 2009 L’Aquila earthquake, in which 308 people were killed, and related this to demographic factors and also to the nature of the damage and collapse of the local building stock (Alexander 2011), with a view to proposing better self-protective behavior.
Koyama et al. (2011) carried out an extensive questionnaire survey in Ojiya City following the 2004 Niigata earthquake in Japan to understand the relationship between location, types and severity of injuries and the arrangement of the building and its furniture, and the activity of the occupants at the time of the earthquake. The aim was to help in loss modelling and to develop strategies for a life-loss reduction strategy. So et al. (2008), with the help of local co-workers, carried out investigations using a survivor questionnaire following the 2005 Pakistan, 2006 Yogjakarta and 2007 Pisco earthquakes to identify the most important causal pathways of injuries and deaths, including examination of types level and causes of injuries, the form of construction and level of damage of the building occupied, and the extent of rescue and post-event treatment available. Figure 1.17 shows the interconnected set of factors found to affect the occurrence of deaths and injuries.
Fig. 1.17
Causes of human casualties in earthquakes: derived from post-earthquake reconnaissance studies by So et al. (2008)
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From such investigations it is clear that it is the level and type of building damage that is the predominant variable affecting death and injury rates, the bulk of casualties occurring when the building not only suffers catastrophic damage, but collapses with significant volume loss. However, many other variables such as time of day, the nature of the ground motion, and the behavior of the occupants can have an important modifying influence on these casualty rates. Working with the USGS PAGER, So (2014) has developed estimates for the likely range of fatality rates which will be associated with building collapse for different classes of building taking account of their likely collapse patterns, to improve casualty estimates provided in the PAGER early post-earthquake alerts, which are now widely used by humanitarian agencies in the planning of emergency response (Jaiswal et al. 2011).
1.8.3 Assembly of Data on Earthquake Consequences
A number of the post-earthquake field missions considered have acquired damage data in a statistical form, either from field surveys or compiled from local reports. This has indeed been a main aim of several EEFIT missions. In the past, the data were made available through the mission-specific publication reports and through the research articles that discuss the observed vulnerability of selected building classes or cross-event summaries (Coburn and Spence 2002). However with the advent of new tools that allow the creation and design of web-accessible data architecture, a much wider accessibility of the data is now possible. Moreover, the publication in 2009 of the USGS ShakeMap archive (http://earthquake.usgs.gov/shakemap), provides an estimate of the ground shaking at any location in any past event. This enables cross-event analyses against a consistent set of estimated ground motions and their variable impacts for the first time. The Cambridge Earthquake Impacts Database (CEQID) (Spence et al. 2011) has been designed and assembled to take advantage of these new tools.
CEQID (www.ceqid.org) is based on earthquake damage data assembled since the 1960s, complemented by other more recently published and some unpublished data. The database assembles the data into a single, organised, expandable and web-accessible format, with a direct access to event-specific shaking hazard maps. Analytical tools are available which enable cross-event relationships between casualty rates, building classes and ground motion parameters to be determined. The Database is freely accessible to all users, and uses a simple xml format suitable for data mining. Location maps and images of damage are provided for each earthquake event. The Database links to the USGS ShakeMap archive to add data on local intensities and on measured ground shaking.
Currently the database contains data on the performance of more than 1.3 million individual buildings, in over 600 surveys following 51 separate earthquakes, and the total is continuously increasing. The database also has a casualty element, which gives total recorded casualties (deaths, seriously and moderately injured), and casualty rates as a proportion of population with definitions of injury levels used, and information on dominant types of injury, age groups affected etc. Of the 51 events currently in the database, 23 were in Asia and the Pacific (12 of which were in Japan), 17 in Europe, Turkey and North Africa, and 11 in North or South America. Most of the surveys have been done in events since 1990; among these 51 events, 18 were prior to 1990, 21 between 1990 and 2000, and 14 since 2000. Of the 1.3 million buildings in the database, 0.45 million do not have a well-defined building or structural typology given; of the remainder, 78 % are of timber frame, 14 % masonry, 5 % reinforced concrete, and 3 % are of other structural types. Thus, in spite of its size, CEQID in its current state is patchy in global coverage, and in terms of building typologies.
The cross event analysis tools of CEQID allow the construction of charts of empirical damage data related to consistent measures of ground motion derived from the USGS Shakemap archive to be used to show the relationship between damage and any chosen measure of ground motion. Thus post-earthquake damage data can be used directly to enable empirical vulnerability relationships to be developed for any given building type, making an important contribution to loss modelling capability.
1.8.4 GEM Earthquake Consequences Database
A more substantial assembly of earthquake consequence data has, over the last 3 years, been taking place within the framework of GEM (the Global Earthquake Model), to complement a series of other hazard and risk components of the model (www.globalquakemodel.org). Like CEQID, GEMECD is also open-access, GIS-based and related to ground motion parameters derived from the USGS shakemap archive, but its scope and the number of events for which data are assembled is wider (So et al. 2012).
GEMECD assembles consequence data of five different categories as follows:
(a)
Ground shaking damage to standard buildings (67 events)
(b)
Human casualty studies and statistics (26 events)
(c)
Ground shaking consequences on non-standard buildings, critical facilities, important infrastructure and lifelines (22 events),
(d)
Consequences due to secondary, induced hazards (landslides, liquefaction, tsunami and fire following) to all types of inventory classes (24 events, 13 of which are related to landslides)
(e)
Socio-economic consequence and recovery data (18 events)
GEMECD has been designed in such a way as to be able to capture the full spectrum of earthquake consequences which can be visualised as a matrix of the interaction between the various inventory assets and the earthquake-related damage agents, as shown in Fig. 1.18. Like CEQID, GEMECD also has cross-event analysis tools which can be used to enable cross-event analyses to be derived for given inventory classes, and levels of ground motion, leading to more robust empirical vulnerability relationships. GEMECD can be accessed at http://www.globalquakemodel.org/what/physical-integrated-risk/consequences-database/
Fig. 1.18
Types of earthquake consequences considered in the GEM Earthquake Consequences database (So et al. 2012)
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1.8.5 Post-Earthquake Image Archives
Photographic images of geological impacts, damaged buildings and facilities have formed an important element of the record of field investigations from the earliest days, from Mallet’s field investigation onwards. Photographs of damage accompany all UNESCO Mission reports though they were not separately archived. Both EERI and EEFIT have compiled photographic datasets from all recent missions, including many images which were not included in mission reports, and these are now available in digital form. Since 2008, ImageCat, MCEER and UCL and several other collaborators have developed the Virtual Disaster Viewer (VDV) (www.virtualdisasterviewer.com) which links geolocated photos and other images with MS Virtual earth maps to provide an online tool for viewing damage and other earthquake effects from a particular event. Data from six earthquakes as well as several windstorm and tsunami events can be viewed.
EEPImap is a new tool, currently under development at Cambridge Architectural Research which forms the first searchable photographic archive of earthquake damage photographs (http://www.eepimap.com). It is based on a georeferenced photographic database containing attributes of individual buildings and other structures and the level of damage sustained. It can be searched online to provide cross-event datasets corresponding to a range of possible facility types and damage attributes. Currently it contains over 15,000 photographs from 40 events including most of those visited by EEFIT, and has facilities for easy uploading of additional data, so it is continually being expanded (Foulser-Piggott 2013). EEPImap is designed to be compatible with risk components of the Global Earthquake Model (GEM).
1.8.6 Use and Limitations of Remote Sensing
Aerial imagery for the identification of areas of serious damage in earthquakes has been used for some years (Saito et al. 2004), and an international consortium of research teams to promote this use has existed since 1994 (Eguchi and Massouri 2005). Since their first availability around 2000, high-resolution optical satellite images as well as aerial images have been increasingly employed for early post-earthquake damage assessments at a building-by-building and local level. The potential benefits of such deployments are considerable: large damaged areas can be surveyed rapidly without being hampered by the emergency operation on the ground; rescue services can be directed to areas or buildings of greatest need; and the extent of damage can be assessed, leading to a valuable early estimate of reconstruction costs or insurance payouts, of value to international aid organizations, bi-lateral/multi-lateral donors and to the insurance industry. Early work established that the human eye is better able to distinguish features of damage than computerised image analysis (Saito et al. 2004), and this has been the basis of much application since then. The Bam earthquake gave a strong spur to such work: 13 separate papers on aspects of remote sensing were submitted to the Earthquake Spectra special issue on that event (Eguchi and Massouri 2005).
The development of web-based crowd-sourcing techniques in recent years has created a further boost to the potential of such methods, enabling a large team of experienced people to share the task of building-by-building assessment over a large damaged area, so that an overall assessment can be produced very rapidly. After the 2010 Haiti earthquake, a team of more than 600 people, the GEOCAN network, was assembled by EERI within a few days of the earthquake, and produced a first damage map of the urban area of Port-au-Prince within a week of the occurrence of the event; and within 3 weeks a second more extensive and detailed study was prepared by the same team, involving damage assessments of 107,000 buildings. The result of this was used for the validation of rapid sample ground-based assessment results carried out for the World Bank/UN/EU Post-Disaster Needs Assessment (Corbane et al. 2011). There are thus considerable financial implications for the accuracy of such estimates.
Following the 2010 Haiti earthquake GEOCAN deployment, an independent on the ground validation exercise took place. The EEFIT reconnaissance mission looked closely on the ground at a very small sample of 142 buildings in the GEOCAN dataset. A new aerial imagery technique, Pictometry, which involves multi-angle images of each location with a horizontal resolution of better than 25 cm, was also used to obtain a further damage dataset of 1241 buildings (Fig. 1.19) (Booth et al. 2011b). After the 2011 Christchurch earthquake, a further GEOCAN deployment took place, identifying damage levels for some 5000 buildings in affected area, and this was able to be assessed against Building Safety Evaluations for these same buildings conducted by the Christchurch City Council (Foulser-Piggott et al. 2014).
Fig. 1.19
Pictometry images of damage in the 2010 Haiti earthquake (Booth et al. 2011a)
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These two studies, though complicated by many methodological difficulties, were able to establish that, although most of the buildings identified by interpretation of the remotely sensed image as being seriously damaged were in reality seriously damaged, much of the heavy damage on the ground, including building collapses, were missed in the remote assessments. Heavy damage and collapse was obscured by vegetation, by proximity to other buildings, because the lower floor of a building collapsed, leaving upper stories and roofs intact, or because major damage ultimately leading to demolition was simply invisible from outside the building. Typically no more than around 40 % of the buildings which ground surveys identified as heavily damaged or collapsed were identified as such in the aerial imagery. The extent of underestimate depended on the resolution of the image, the level of experience of the image analyst, the construction typology of the building, and the type of damage. Damage to masonry buildings was easier to identify than that to either timber frame or reinforced concrete buildings; damage caused by foundation failure or subsoil liquefaction (a very important class of damage in the Christchurch earthquake) proved particularly difficult to identify (Foulser-Piggott et al. 2014).
Many recommendations were made as a result of these studies to improve the results of future remotely-sensed damage assessments; and improvements in the quality of the available imagery will certainly continue to be made. Indeed it is probable that photography from low-level pilotless aircraft will in the near future be able to augment substantially the remotely sensed data available. But remote sensing cannot in the near future be expected to become a substitute for post-earthquake field reconnaissance. Assessments from remote sensing can be very useful to identify areas where damage is concentrated; to identify blocked roads and collapsed bridges; to identify areas of liquefaction (especially where these are associated with sand boils), and major landslides. They can also be used to make an approximate assessment of overall damage if enough is known about the likely omission errors in such assessments. But the detail of damage, the performance of different construction typologies, and the relationship of damage to quality of construction will continue to need investigations by experienced observers on the ground, at close quarters to, and where possible inside, the damaged buildings. Future remote sensing assessments should be planned to be coupled with field deployments to validate the results and to provide more of the detail which remote sensing cannot supply.
1.9 The Future of Earthquake Field Missions
Over the last 30 years there has been a huge change in the technology available to support earthquake field missions. Digital photography, GPS positioning, the internet, mobile phone networks, high resolution satellite reconnaissance, social media have all arrived and made their mark on the way earthquake reconnaissance missions are conducted. This is in contrast to the construction technologies whose performance is being investigated, which have changed comparatively little in that time. Technology will continue to evolve at a rapid pace in both predictable and unpredicted ways, allowing improvements in speed of operation, in communication between team members and base, and in the capturing of detail: through photographic communication, some people will be able to contribute to the work of field missions without travelling to the affected area. For example, developments such as EEPI Map will allow for the crowdsourcing of photographs from general members of the public which can be assessed remotely and can help produce a rapid damage assessment of an area.
As discussed above, the development of higher-resolution and other forms of remote sensing is not likely to eliminate the need for investigators in the field to view damage from close range. But it will enable teams to organise their field operations with support from continuously updated and pre-analysed remote sensing images. The development of databases of the building stock inventory (already in development through the GEM project) will enable teams to have access to pre- event data and images of each damaged object. As a response to such changes field teams may in future be smaller, more focussed on special aspects and deployed at different times.
The collection of building-by-building data on damage has been an important feature of the work of some reconnaissance missions, and it is largely through such damage surveys that empirical fragility relationships for loss estimation have been developed. It is often assumed by reconnaissance teams that detailed building damage surveying will be done, over time, by national authorities and made available. But such official damage data often turns out to be inadequate for use in loss estimation, with damage levels and construction typologies poorly defined, and undamaged buildings often omitted. Assembling damage data through well-chosen local building-by-building sample datasets will continue to be of vital importance, and field surveys can now be supported through remote sensing to locate appropriate samples across a range of areas, not just those most heavily damaged.
There is still a need to improve the level of international collaboration between field mission teams. Table 1.1 shows that the sites of a number of the most important earthquakes in recent years have been visited by multiple teams, which usually work independently of each other. In many of the affected countries significant expertise in earthquake engineering now exists, and it is vital for visiting reconnaissance teams to work with local experts, to learn from them, and share their own knowledge. This already happens, but should be extended in future.
Recent events have shown that in many parts of the world, especially in poorer countries, there is an urgent need to improve the earthquake resistance of much of the existing building stock, as well as improve the standards of new buildings for the future. Thus future post-earthquake field missions are likely to be as much concerned with helping with developing resilience as recording damage: this will give rise to a need for a series of missions at different stages of the recovery cycle, and the involvement of more expertise from complementary disciplines such as sociology and urban planning. EEFIT and EERI already have funding in place permitting such operations. Given the probability of large urban disasters in the future it is important that field mission organisations make plans to be able to mount field missions in potentially challenging situations (such as that in Haiti in 2010). It may also be that established field mission teams, now already familiar with studying tsunami impacts, should consider mounting, or supporting, field investigations following non-earthquake disasters such as volcanic eruptions or major typhoons where there is a similar need for rapid deployment to assemble perishable data.
1.10 Conclusions
This paper set out to review the nature and practice of earthquake reconnaissance missions since the earliest examples to today’s practice, and to point out some of the ways in which the practice of earthquake engineering today has benefitted from field observations.
After a brief historical background the paper has concentrated on the missions of 5 separate groups, active in the last 50 years, those of UNESCO, EERI, EEFIT and more briefly the Japanese Society for Earthquake Engineering, AFPS in France and the German Task force, all of whom have been involved in multiple international missions in that time.
Between these teams, 258 post-earthquake reconnaissance missions have been mounted , and they have investigated, and have reported on, 178 separate events. Of these 37 were in the European area, 64 in Asia, 64 in the Americas, 7 in Africa, and 6 in Australasia and the Pacific. The style of mission has varied considerably, from the small expert interdisciplinary scientist/engineer teams of UNESCO spending several weeks in the field to today’s larger, more multidisciplinary teams with many specialists, but often on shorter initial missions sometimes backed by follow-up studies.
Reports on each mission have been prepared and those of current teams are available on their websites which have been referenced; often these have been accompanied by published papers.
The cumulative contribution of these field teams to earthquake engineering , seismology and to understanding the social and economic consequences of earthquakes has been considerable, leading to improved design codes and design practices, to better understanding of human behaviour and guidance to inhabitants of earthquake zones, and the accumulation of data on earthquake consequences enabling estimation of possible losses in future events to be made.
An important benefit to recent field studies has been the increasing availability of strong motion records of earthquakes, making it possible to link damage observations to the level and characteristics of the causative ground motion.
For engineered buildings, repeated observations of the same types of damage in many earthquakes has driven the development of the current generation of design codes; buildings designed and built to these codes have largely performed well in subsequent earthquakes.
Field investigations of the distribution of damage coupled with the increasing availability of strong ground motion recordings of the main shock and aftershocks, has led to a better understanding of the role played by site conditions on the amplification of ground motion and the types and distribution of damage to structures.
The data on performance of lifelines assembled by field missions has identified both systems that have performed well and those that failed; and has resulted in numerous changes to design practices.
Studies of the behaviour of people and communities has made numerous contributions to preparedness planning, to organisation of search and rescue and to the improved planning of longer-term recovery.
The differences in the performance of domestic scale non-engineered structures of different forms of construction has become better understood, enabling guidelines to be developed for safer reconstruction in especially rural areas, and leading to effective building for safety programmes in reconstruction.
The likely mechanisms of collapse of historical masonry buildings have been identified, and some inappropriate earlier attempts at strengthening measures identified, leading to the development of appropriate techniques for strengthening and protecting historical monuments.
The causes of human casualties resulting from building damage in earthquakes have become better understood, enabling better early estimation of likely losses, better design of effective measures for self-protection of the population, and better planning for early search and rescue activity.
The data acquired from past field missions has in recent years become more systematically documented and archived using web-based database technology, so that data can easily be accessed and retrieved, and so that cross-event analysis of damage and other impacts to particular components of the built environment , social and economic activities can be conducted.
Remote sensing technology has begun to make a contribution to the recording of earthquake damage, making possible early assessments of likely impacts. Much remains to be done to realise the full potential of these technologies, but their application will enhance rather than replace field investigations.
Future field missions will make use of rapidly developing technology for viewing, recording and communicating mission activities. They will be more interdisciplinary, carry out repeat missions, and concerned increasingly with developing resilience. They should not abandon collection of building-by-building damage data through local surveys.
Acknowledgements
The author is greatly indebted to contributions from a numbers of colleagues who have reviewed parts of this paper and provided additional background material, notably Roger Musson, James Jackson, Edmund Booth, Marjorie Greene, Antonios Pomonis, Dina D’Ayala, John Douglas, Vicki Kouskouna, Roxane Foulser-Piggott, Emily So, Sean Wilkinson, Göcke Tonuk and Sebastian Hainzl. The maps and tables of mission locations were prepared by Hannah Baker.
