Understanding Seismic Hazard Needs for Infrastructure Risk Analysis: Lessons from SYNER-G

Transcription

1 Systemic Seismic Vulnerability and Risk Analysis for Buildings, Lifeline Networks and Infrastructures Safety Gain Understanding Seismic Hazard Needs for Infrastructure Risk Analysis: Lessons from SYNER-G Graeme Weatherill 1, Simona Esposito 2, Iunio Iervolino 2, Paolo Franchin 3 1 European Centre for Training & Research in Earthquake Engineering (EUCENTRE), Pavia, Italy 2 Università degli Studi di Napoli Federico II, Naples, Italy 3 University of Roma La Sapienza, Rome, Italy 1

2 The Conceptual Challenge 2

3 The Conceptual Challenge Susceptible to slope displacement Active Fault Susceptible to liquefaction 3

4 The Conceptual Challenge Susceptible to slope displacement Active Fault Susceptible to liquefaction 4

5 The Conceptual Challenge Susceptible to slope displacement Active Fault Susceptible to liquefaction 5

6 The Conceptual Challenge Active Fault Coseismic Displacement Slope Displacement Liquefaction System 1 = {{X 1, X 2, X N1 }, { }} System 2 = {{Y 1, Y 2, {X 1, X 4 }, Y N2 }, { }} Elements in both systems are typically heterogeneous. Fragility models may be dependent on different periods of ground motion and/or permanent ground deformation (d f ) 6

7 Uncertainty and Correlation Probabilistic system risk analysis must incorporate the aleatory uncertainty in the seismic hazard For a spatially distributed system(s) of heterogeneous elements need to consider correlations between ground motion intensity levels (IMs) at different sites: Spatial correlation: ρ 11 (h) IM to IM cross-correlation: ρ 12 (0) Spatial cross-correlation: ρ 12 (h) IMs also include geotechnical hazards ideally should consider aleatory uncertainty here too! Monte Carlo approach adopted 7

8 The Shakefield Approach Monte Carlo Simulation Generation of spatially correlated and crosscorrelated fields for ground motion intensity measures (IMs) i.e. PGA, PGV, Sa Multiple source typologies Area sources Simple Fault Sources Extension to geotechnical hazard 8

9 Spatial Correlation Each Shakefield samples a spatially correlated multivariate Gaussian field of ground motion residuals. log Y ij ( ) = f ( M i, R ij,q i1,i 2, in ) +e ij +h ij Sites can be distributed across a regular grid, or as a list of locations Spatial correlation model of Esposito & Iervolino (2010; 2011) using ground motion residuals referred to Akkar & Bommer (2010) 9

10 Spatial Cross-Correlation Spectral correlation model of Baker & Cornell (2006) preferred in this application Choice of spatial and of spectral correlation models could be explored within the epistemic uncertainty analysis 10

11 Site Amplification Possible Approaches Design code amplification factors NEHRP/IBC (2003/2006) Eurocode (2004), or adjusted (Pitilakis et al., 2012) factors Ground Motion on Rock Direct Calculation using Vs30 or GMPE site class Empirical Amplification Models Choi & Stewart (2005) Site-specific response analysis 11

12 Landsliding and Liquefaction HAZUS classifications retained for liquefaction and slope displacement susceptibility categories and for corresponding probability definitions - Slope displacement model replaced with Saygill & Rathje (2008) Landslide/Liquefaction occurrence probabilities sampled within stochastic framework 12

13 Coseismic Rupture Translation of Probabilistic Fault Displacement Hazard Assessment (PFDHA) (Youngs et al., 2003) methodology into stochastic framework: Earthquake rate and recurrence model P kn (s m,r) probability of slip at site, given magnitude and distance (1) P kn (D > d m, r, s) probability displacement exceeds D, given m, r, and slip at surface (2) Software samples (1) within the stochastically generated finite ruptures Displacements estimated from empirical models of principal and distributed fault rupture 13

14 Geotechnical Hazard Calculators Geotechnical calculators extend Shakefield to consider permanent ground displacement Some aleatory uncertainty is currently considered: Sampling probabilities of observing liquefaction/slope displacement Sampling aleatory uncertainy in empirical slope displacement model Full stochastic implementation of probabilistic fault displacement hazard Spatial correlations in geotechnical hazards not considered! 14

15 In Summary SYNER-G software (OOFIMS) includes a full stochastic seismic hazard calculator including: 1. Spatial Cross-Correlation in Ground Motions 2. Site amplification 3. Permanent ground deformation from landsliding and liquefaction 4. Permanent ground deformation from co-seismic rupture Despite objectives of practicality, considerable information is needed to implement some of the methods effectively Future work should focus on: Incorporating spatial elements of site-response analysis Exploring spatial correlations in geotechnical hazards 15