Developing Next Generation PFDHA and Confidence Limits on Geologic Slip Rates Using High-Resolution Geodetic Imaging Data

Date: 4/25/2019

Time: 08:30 AM

Room: Pike

Understanding how inelastic, co-seismic shear strain decreases with distance from the primary fault rupture is important for accurately characterizing the hazard it poses to the critical infrastructure and estimating the full geologic slip rate. Probabilistic Fault Displacement Hazard Analysis (PFDHA), estimates the exceedance probability of distributed faulting off the primary fault, and has so far been constrained solely from traditional field observations of surface ruptures. Here we assess how measurements of the near-field surface deformation pattern of several large magnitude earthquakes (M_w > 7), derived from different geodetic imaging techniques (optical image and radar amplitude correlation), can be used to better constrain the ‘fall-off’ of inelastic strain away from the primary fault. From the high-resolution displacement maps we can measure the full across-fault surface strain at multiple points along the surface rupture (n>1000 for each event), providing a more consistent and reliable estimate of the probability of occurrence of inelastic deformation and exceedance with distance from the fault, both key terms in the PFDHA hazard equation. From the correlation maps we also investigate how parts of the rupture undergoing compression and extension effects the distribution of inelastic strain across the surface rupture. We then discuss how our probability estimates of strain width derived from surface ruptures can characterize the probability a geologic slip rate measurement captures the full, across-fault geologic strain release. High-resolution geodetic measurements of near-field deformation from surface ruptures can help better quantify the aleatory variability and reduce the epistemic uncertainty in PFDHA models, providing more precise information to structural engineers, and place empirical uncertainties on geologic slip rates, an important input for Probabilistic Seismic Hazard Assessment.

Presenting Author: Christopher W. D. Milliner

Authors