Doubly Stochastic Models for Volcanic Hazard Assessment at Campi Flegrei Caldera

verfasst von: Andrea Bevilacqua

Verlag: Scuola Normale Superiore

Buchreihe : CRM Series

Enthalten in: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik" , Springer Professional "Wirtschaft"

Einloggen, um Zugang zu erhalten

Über dieses Buch

This study provides innovative mathematical models for assessing the eruption probability and associated volcanic hazards, and applies them to the Campi Flegrei caldera in Italy. Throughout the book, significant attention is devoted to quantifying the sources of uncertainty affecting the forecast estimates.

The Campi Flegrei caldera is certainly one of the world’s highest-risk volcanoes, with more than 70 eruptions over the last 15,000 years, prevalently explosive ones of varying magnitude, intensity and vent location. In the second half of the twentieth century the volcano apparently once again entered a phase of unrest that continues to the present. Hundreds of thousands of people live inside the caldera and over a million more in the nearby city of Naples, making a future eruption of Campi Flegrei an event with potentially catastrophic consequences at the national and European levels.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introduction

Abstract

Volcanic eruptions are the surface discharges of gas and magma (e.g. [129, 30]), which is a mixture of molten rock, suspended crystals and dissolved gas; it sometimes includes also gas bubbles and rock fragments (see Figure 1.1). Magma has complex properties that reflect the changing proportions of its components and chemistry, and it is capable of intrusion into adjacent rocks forming dikes and sills, extrusion onto the surface as lava, and explosive ejection as tephra to form pyroclastic rock (see [73, 83, 84]). The widely accepted qualitative model for a volcanic system assumes the presence of one or more magma reservoirs below the surface (e.g. [103]), that may become over-pressurized because of the injection of new high temperature magma or because of a structural weakening of the surrounding rock, hence overcoming the critical pressure required for the propagation of magma to the surface, opening a vent (or fissure) and erupting (e.g. [146, 102, 149]). A volcano is any geographical feature built by volcanic eruptions (e.g. [144, 52]).

Andrea Bevilacqua

Chapter 2. Vent opening probability maps

Summary

Campi Flegrei is an active volcanic area situated in the Campanian Plain (Italy) and dominated by a resurgent caldera. The great majority of past eruptions have been explosive, variable in magnitude, intensity and in their vent locations. In this chapter we present a probabilistic analysis using a variety of volcanological datasets to map the background spatial probability of vent opening conditional on the occurrence of an event in the foreseeable future. The analysis focuses on the reconstruction of the location of past eruptive vents in the last 15 ka, including the distribution of faults and surface fractures as being representative of areas of crustal weakness (see Figure 2.1). One of the key objectives is to incorporate some of the main sources of epistemic uncertainty about the volcanic system through a structured expert elicitation, thereby quantifying uncertainties for certain important model parameters and allowing outcomes from different expert weighting models to be evaluated.

Andrea Bevilacqua

Chapter 3. Pyroclastic density current invasion maps

Summary

Campi Flegrei is an active caldera containing densely populated settlements at very high risk of pyroclastic density currents (PDCs). We present here an innovative method for assessing background spatial PDC hazard with probabilistic invasion maps conditional on the occurrence of an explosive event. The method encompasses the probabilistic assessment of potential vent opening positions, derived in the previous chapter, combined with inferences about the spatial density distribution of PDC invasion areas from a simplified flow model, informed by reconstruction of deposits from eruptions in the last 15 ka. The flow model describes the PDC kinematics and accounts for main effects of topography on flow propagation. Structured expert elicitation is used to incorporate certain sources of epistemic uncertainty, and a Monte Carlo approach is adopted to produce a set of probabilistic hazard maps for the whole Campi Flegrei area.

Andrea Bevilacqua

Chapter 4. Time-space model for the next eruption

Summary

The main objective of this chapter is developing a robust temporal model capable of producing a background (long-term) probability distribution for the time of the next explosive eruption at Campi Flegrei. In the last 15 ka, intense and mostly explosive volcanism has occurred within and along the boundaries of the caldera (see Chapter 2; e.g. [97]). Eruptions occurred closely spaced in time, over periods from a few centuries to a few millennia, and were alternated by periods of quiescence lasting even several millennia; sometimes events also occurred closely in space thus generating a cluster of events (e.g. [96]). As a consequence, activity has been generally subdivided into three distinct epochs, i.e. Epoch I, 15 – 10.6 ka; Epoch II, 9.6 – 9.1 ka, and Epoch III, 5.5 – 3.8 ka BP (e.g. [122, 145]). The most recent Monte Nuovo eruption (e.g. [56, 58, 79]) occurred in 1538 AD after more than 2.7 ka from the previous one. Unfortunately, there is a remarkable epistemic uncertainty on the eruptive record, affecting the time of eruptions, location of vents as well as the erupted volume estimates. Other studies including information about the time-space eruptive behaviour of Campi Flegrei are [133, 139, 57, 54].

Andrea Bevilacqua

Chapter 5. Addendum

Summary

In this Chapter are included three detailed digressions about important topics concerning the mathematical and physical background of the previous chapters. In particular is presented a general introduction to the expert elicitation theory, then the complete construction of the simplified model adopted for propagating pyroclastic density currents (box model), and at last a summary about Cox processes and Hawkes processes.

Andrea Bevilacqua

Chapter 6. Supporting information

Summary

In this chapter we include additional material concerning some technical details of the study. First it is reported the seed questionnaire that was adopted for obtaining the experts’ scores (from W.P Aspinall, personal communication), the list of the true values is available on request. Then there is the complete and anonymous response list given by each expert to the seed and the target questions, including some range graphs of the results. After that are reported all the most important computer codes that were implemented during this study: all of them have been developed in the R software environment (e.g. [135]) and are referred as R-codes. At last there is a list of the principal symbols adopted in this study.

Andrea Bevilacqua

Backmatter

Titel: Doubly Stochastic Models for Volcanic Hazard Assessment at Campi Flegrei Caldera
verfasst von: Andrea Bevilacqua
Verlag: Scuola Normale Superiore
Electronic ISBN: 978-88-7642-577-6
Print ISBN: 978-88-7642-556-1
DOI: https://doi.org/10.1007/978-88-7642-577-6