An Overview of the SIGMA Research Project: A European Approach to Seismic Hazard Analysis (Geotechnical, Geological and Earthquake Engineering (42))

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. Contents 7 Acronyms 11 Chapter 1: Introduction 12 1.1 Overview of the Project Organisation 12 1.2 Object of the Document 15 References 15 Chapter 2: General Concepts and PSHA Background 16 2.1 Development of a Seismotectonic Framework for PSHA 16 2.2 Development of Seismic Sources and Logic Trees for Source Definition 17 2.3 Site Specific vs. Regional Study 17 2.4 PSHA – A Framework for Seismic Source & Ground Motion & Site Response Characterization 19 2.5 Logic Tree Approach and Treatment of Uncertainties 23 2.5.1 Epistemic Uncertainty vs. Aleatory Variability 23 2.5.2 Logic Tree Methodology 24 2.5.3 Site Response 25 2.5.3.1 Methods for Implementing Site Response Effects 25 2.5.4 Use of Experts 27 2.5.4.1 Guidance Regarding Expert Elicitations 28 2.6 Interface Issues Between Work Packages 29 2.7 Common Required Outputs for Seismic Hazard Results 29 2.7.1 Basic Definitions and Requirements 30 2.7.1.1 Control Point 30 2.7.1.2 Components of Motion 30 2.7.1.3 Vibration Frequencies for Hazard Analysis 30 2.7.1.4 Lowest Annual Probability of Exceedance 31 2.7.2 Common Hazard Results 31 2.7.2.1 Seismic Hazard Curves for Reference Rock Site Condition 31 2.7.2.2 Seismic Hazard Curves for the Soil Site Condition 31 2.7.2.3 Epistemic Uncertainty in the Soil Hazard Curves 32 2.7.2.4 Uniform Hazard Spectra 32 2.7.2.5 Disaggregation 32 2.7.3 Additional Parameters 33 2.7.3.1 Ground Motion Duration 33 2.7.3.2 Peak Ground Velocity 33 2.7.3.3 Cumulative Absolute Velocity 33 References 34 Chapter 3: Seismic Source Characterization 35 3.1 Pre-requisites to Develop the SSC Models 36 3.2 Database, Earthquake Catalogue, Magnitude Conversions, Uncertainties on Metadata 38 3.3 Seismic Source Models 42 3.3.1 Diffuse Seismicity Versus Identified Seismogenic Structures 42 3.3.2 Seismic Source Characterization Framework 43 3.3.3 Area Source, Fault Sources, Gridded Seismicity 44 3.3.3.1 Area Sources 44 3.3.3.2 Fault Sources 45 3.3.3.3 Gridded/Smoothed Seismicity 48 3.3.4 Lessons Learned Related to Seismic Source Models 50 3.4 Occurrence Processes 51 3.4.1 Poisson Model 51 3.4.2 Characteristic Model 52 3.4.3 Time-Dependent Seismicity Models 52 3.5 Maximum Magnitude and Recurrence Parameters 52 3.5.1 Maximum Magnitude 52 3.5.2 Recurrence Parameters 54 3.5.3 Lessons Learned 55 3.6 Logic-Tree Implications 57 3.6.1 Logic Tree Approaches 57 3.6.2 Efficient Tools for the Logic Tree Conception and Weights Assignment 59 3.6.2.1 Pilot Model for an Interaction and Interface Management Between Components of the PSHA 59 3.6.2.2 Disaggregation 60 3.6.2.3 Sensitivity Analyses 60 3.6.2.4 Testing the Branches of the Logic Tree Using Data and Observations 62 3.6.3 Verification and Quality Assurance (QA) 63 References 63 Chapter 4: Rock Motion Characterization 66 4.1 Empirical Models and Point Source Stochastic Models 66 4.1.1 Empirical Ground Motion Attenuation Models 66 4.1.2 Point Source Stochastic Models 71 4.2 Model Selection and Criteria 72 4.2.1 Modelling Criteria 72 4.2.2 Tectonic Consistency 73 4.2.3 Site-Conditions Consistency 75 4.3 Corrections or Modifications of Published Models 75 4.3.1 κ-VS30 (Simulation-Based) Correction 76 4.3.2 Data-Based Predictions for Hard Rock 80 4.4 Standard Deviation of Model Predictions; Truncation 82 4.4.1 Sigma Truncation 85 4.5 Approaches for the Vertical Ground Motion Component 87 4.6 Logic Tree Implications 88 4.7 Lessons Learned from the SIGMA Project 89 References 90 Chapter 5: Site Response Characterization 93 5.1 Soil Characterization 93 5.1.1 Determination of the Profile Natural Frequency f0 94 5.1.2 Determination of the Shear-Wave Velocity Profile and Site Class 94 5.1.3 Seismic Instrumentation 99 5.1.4 Characterization of Nonlinear Soil Properties 100 5.2 Hazard Assessment at the Ground Surface 101 5.2.1 Direct Evaluation from Ground Motion Prediction Equations (FpG) 104 5.2.2 Generic Site Specific Approaches (HyG) 105 5.2.2.1 Correction to Rock Spectrum 106 5.2.2.2 Correction to Ground Surface Spectrum 108 5.3 Completely Site Specific Approaches (HyS) 109 5.3.1 Linear Numerical Analyses 111 5.3.2 Equivalent Linear Numerical Analyses 112 5.3.3 Nonlinear Numerical Analyses 115 5.4 Treatment of Uncertainties 119 5.4.1 Fully Probabilistic Generic Site Approach (FpG) 119 5.4.2 Hybrid Site Specific Approach (HyS) 120 5.4.2.1 Uncertainty Related to Selection of Input Motions 121 5.4.2.2 Uncertainty in VS Profiles 121 5.4.2.3 Uncertainty in Soil Behaviour Modelling 121 5.4.2.4 Combination of Epistemic Uncertainties 122 5.5 Lessons Learned from the SIGMA Project 122 5.6 Additional Topics in Ground Surface Hazard Assessment 123 5.6.1 Vertical Ground Motion 123 5.6.2 Maximum Ground Motion: Truncation 124 References 125 Chapter 6: Seismic Hazard Computation 127 6.1 Basic Requirements 127 6.2 Interfaces and Boundary Conditions 128 6.3 Software Packages 128 6.3.1 PSHA Software 128 6.3.2 Site Response Analysis Codes 130 6.4 Sensitivity Analysis 131 6.5 Hazard Disaggregation 134 6.6 Additional Engineering Output Parameters 135 6.7 Selection of Time Histories 136 6.7.1 Selection Based on UHS 136 6.7.2 Selection Based on Conditional Spectra 137 References 138 Chapter 7: Interfaces Between Subprojects 141 7.1 SSC and GMC Interfaces 141 7.2 GMC and SRC Interfaces 143 7.3 Single-Station Sigma 145 7.4 V/H Models for Rock and Soil 146 References 147 Chapter 8: Probabilistic Seismic Testing and Updating of Seismic Hazard Results 148 8.1 PSHA Testing Using Acceleration and Macroseismic Intensity Data 149 8.2 Bayesian Update of PSHA 152 References 152 Chapter 9: Summary and Way Forward 154 9.1 Seismic Source Characterization 154 9.2 Ground Motion Characterization 155 9.3 Site Response Characterization 155 9.4 Hazard Calculation 156 9.5 Risk Assessment 156 Annexes 157 Annex 1: List of Committees Members 157 Steering Committee 157 Senior Hazard Analysis Review Panel-SHARP 157 Scientific Committee 157 SIGMA Work Package Leaders 158 SIGMA Partners 159 Annex 2: List of Publications 160 Publications in International Journals with Peer Review 160 Full Papers in Peer-Reviewed Conferences 164 PhD Theses 165 List of Deliverables 166 Bibliography 170 Index 174 Front Matter....Pages i-xi Introduction....Pages 1-4 General Concepts and PSHA Background....Pages 5-23 Seismic Source Characterization....Pages 25-55 Rock Motion Characterization....Pages 57-83 Site Response Characterization....Pages 85-118 Seismic Hazard Computation....Pages 119-132 Interfaces Between Subprojects....Pages 133-139 Probabilistic Seismic Testing and Updating of Seismic Hazard Results....Pages 141-146 Summary and Way Forward....Pages 147-149 Back Matter....Pages 151-172