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2017 | Book

Introduction Read chapter Read first chapter

An Overview of the SIGMA Research Project

A European Approach to Seismic Hazard Analysis

Authors: Alain Pecker, Ezio Faccioli, Aybars Gurpinar, Christophe Martin, Philippe Renault

Publisher: Springer International Publishing

Book Series : Geotechnical, Geological and Earthquake Engineering

Part of: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik" , Springer Professional "Wirtschaft"

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About this book

This book presents a summary of the important outcomes of the SIGMA project related to all aspects of Probabilistic Seismic Hazard Assessment: source characterization, rock motion characterization, site response characterization, and hazard calculations, with for all of them emphasis on the treatment of uncertainties.

In recent years, attempts have been made to identify and quantify uncertainties in seismic hazard estimations for regions with moderate seismicity. These uncertainties, for which no estimation standards exist, create major difficulties and can lead to different interpretations and divergent opinions among experts. To address this matter, an international research project was launched in January 2011, by an industrial consortium composed of French and Italian organizations. This program, named SIGMA (Seismic Ground Motion Assessment) lasted for five years and involved a large number of international institutions.

This book is intended for instructors running courses on engineering seismology, graduate students in the same field and practicing engineers involved in Probabilistic Seismic Hazard Analyses.

Table of Contents

Frontmatter
Chapter 1. Introduction
Abstract
In recent years, attempts have been made to identify and quantify uncertainties in seismic hazard estimations for regions with moderate seismicity. These studies have highlighted the lack of representative data, thereby resulting in predictions of seismic ground motion with large uncertainties. These uncertainties, for which no estimation standards exist, create major difficulties and can lead to different interpretations and divergent opinions among experts. There is a wide consensus among the scientific and technical community for the need to improve knowledge so as to better characterize and, ideally, reduce the uncertainties entering in the calculation of seismic ground motion hazard.
Alain Pecker, Ezio Faccioli, Aybars Gurpinar, Christophe Martin, Philippe Renault
Chapter 2. General Concepts and PSHA Background
Abstract
The first step in building the PSHA model is the collection of geological, geophysical, geotechnical and seismological data from published and unpublished documents, theses, and field investigations. These data are integrated to develop a coherent interpretation of a seismotectonic framework for the study region. Its size can vary depending on the purpose. The international practice for a site-specific study is to distinguish between the investigations at a regional, near regional and site vicinity level (e.g. 300 km, 25 km and 5 km radius in IAEA SSG-9, IAEA (2010)). In order to include all features and areas with significant potential contribution to the hazard, it may also be necessary to include information in a radius up to 500 km (e.g. for subduction zones). This framework provides the guiding philosophy for the identification of seismic sources. Furthermore, the framework should address the important issues that each expert expects to influence the identification and characterisation of seismic sources in the region. The main topics to be addressed in the seismotectonic framework include:
  • Use of pre-existing geological structures to provide a basis for defining the present and future seismicity.
  • Tectonic models that are applicable to contemporary processes, the observed seismicity, and are compatible with seismic sources.
  • Spatial distribution of the seismicity in three dimensions, and associated focal mechanisms and their relation to potential seismic sources.
  • Implications of contemporary stresses and strains (e.g. earthquake focal mechanisms, geodetics, other kinematic constraints) for defining sources.
  • Use of historical and instrumental seismicity and seismic source delineation to provide a basis for defining the locations of future earthquake activity.
Alain Pecker, Ezio Faccioli, Aybars Gurpinar, Christophe Martin, Philippe Renault
Chapter 3. Seismic Source Characterization
Abstract
Seismic sources characterization (SSC) relies on the interpretation and integration of a variety of parameters and data primarily collected in a geological, geophysical, geotechnical and seismological database (D4-41, Carbon et al. 2012). It has three fundamental objectives:
  • The identification (location and geometry) of all seismic sources contributing to the total hazard at the site of interest. According to the seismotectonic context of the site, and to the considered hazard return period, this involves developing the database within a radius of a few hundred kilometres around the site and to consider different scales of analysis especially when individual faults are considered.
  • The characterization of the seismic activity with a large number of uncertain parameters: the maximum magnitude of these seismic sources, their activity rate and the models for seismicity distribution.
  • The consideration of all inherent epistemic and aleatory uncertainties and the influence of the different uncertainties in the hazard results.
Alain Pecker, Ezio Faccioli, Aybars Gurpinar, Christophe Martin, Philippe Renault
Chapter 4. Rock Motion Characterization
Abstract
As stated in Chap. 2, rock (as well as soil) ground motion characterization for PSHA requires that both the median response spectral acceleration and its standard deviation (aleatory variability) be estimated by appropriate algorithms, such as GMPEs or stochastic models. In Sect. 2.​5 of Chap. 2 the logic tree approach was introduced for handling epistemic uncertainty, pointing out that the dynamic characteristics of the earthquake source and wave propagation near the site are typical sources of uncertainty in ground-motion prediction. Some implications for the logic tree treatment of epistemic uncertainty of rock ground motion will be discussed at the end of this chapter.
Alain Pecker, Ezio Faccioli, Aybars Gurpinar, Christophe Martin, Philippe Renault
Chapter 5. Site Response Characterization
Abstract
It is well recognized that the seismic response of a site is strongly dependent on the local geological and geotechnical features of the ground profile. Several approaches are available to include site response effects in the hazard assessment. They are detailed in the following paragraphs but all of them require more or less in-depth knowledge of the geotechnical characteristics. Such knowledge can only be acquired through sit investigations. Therefore, a considerable amount of efforts has been devoted in SIGMA to investigating the reliability of several site investigation techniques, whose level of complexity depends on the choice of the site effect evaluation method; characterization is also mandatory to get the minimum information to choose the method itself.
Alain Pecker, Ezio Faccioli, Aybars Gurpinar, Christophe Martin, Philippe Renault
Chapter 6. Seismic Hazard Computation
Abstract
This section deals with the seismic hazard computation process. It should be noted that, in cases where the seismic hazard to be calculated includes site-specific soil amplifications, this process may include two steps: hazard calculation for reference rock conditions and subsequent site response analysis to combine the local soil response with the rock hazard (see Sect. 5.​2).
Alain Pecker, Ezio Faccioli, Aybars Gurpinar, Christophe Martin, Philippe Renault
Chapter 7. Interfaces Between Subprojects
Abstract
Interface issues between the seismic source characterization and the ground motion characterization are usually implicitly handled by the hazard computation. Nevertheless, the most relevant interface topics, for example the depth distribution and the distance metric, should be discussed among experts from both sides of the interface. In the following sections, the interface issues identified as the most important for the hazard are discussed briefly.
Alain Pecker, Ezio Faccioli, Aybars Gurpinar, Christophe Martin, Philippe Renault
Chapter 8. Probabilistic Seismic Testing and Updating of Seismic Hazard Results
Abstract
Considering the high uncertainties in PSHA and the importance of PSHA results for seismic design and retrofit, it is pertinent to focus on the issue of consistency checking of the PSHA results. In the last decade several approaches to test PSHA results have been published (e.g. Stirling and Petersen 2006; Stirling and Gerstenberger 2009, 2010; Stirling 2012; Mucciarelli et al. 2008; Humbert and Viallet 2008; Labbé 2010; Anderson et al. 2011; Mezcua et al. 2013; Selva and Sandri 2013; Gribovszki et al. 2013). In addition, several recent opinion papers are encouraging hazard analysts to carry out tests of PSHA results (e.g. Stein et al. 2011). During the SIGMA period an international workshop was held in Pavia (NEA 2015) on “Testing PSHA results and Benefit from Bayesian Techniques for Seismic Hazard Assessment” which concluded that a state-of-the-art PSHA should include a testing phase against any available observation, including any kind of observation and any period of observation, including instrumental seismicity, historical seismicity and paleoseismicity data if available. It should include testing not only against its median hazard estimates but also against their entire distribution (percentiles).
Alain Pecker, Ezio Faccioli, Aybars Gurpinar, Christophe Martin, Philippe Renault
Chapter 9. Summary and Way Forward
Abstract
During 5 years SIGMA has not only achieved significant steps forward in the methods for evaluating seismic hazard at a site, but it also contributed to establishing a strong network of academic institutions, researchers and engineering companies that will survive after the project ends. The overall organisation of the project fostered very lively and fruitful discussions between all participants, including with the members of the Scientific and Steering Committees.
Alain Pecker, Ezio Faccioli, Aybars Gurpinar, Christophe Martin, Philippe Renault
Backmatter
Metadata
Title
An Overview of the SIGMA Research Project
Authors
Alain Pecker
Ezio Faccioli
Aybars Gurpinar
Christophe Martin
Philippe Renault
Copyright Year
2017
Electronic ISBN
978-3-319-58154-5
Print ISBN
978-3-319-58153-8
DOI
https://doi.org/10.1007/978-3-319-58154-5