Development of a Geodetic-Based Probabilistic Fault Displacement Hazard Analysis Using Near-Field Geodetic Imaging Data: Examples from the 2019 Ridgecrest Earthquake Sequence

Session: Observations From the 2019 Ridgecrest Earthquake Sequence
Type: Oral
Date: 4/28/2020
Time: 03:15 PM
Room: 115
Description: 

Understanding how inelastic, co-seismic shear strain attenuates with distance away from the primary fault rupture is important for accurately characterizing the hazard it poses to critical infrastructure and estimating the full geologic slip rate. Probabilistic Fault Displacement Hazard Analysis (PFDHA), is a method that estimates the exceedance probability (or annual rate) of distributed rupture at some distance away from the primary fault. However, this empirical approach is currently constrained using traditional field survey observations of past surface ruptures which can be subjective, have unknown uncertainty and are typically spatially sparse. Here we present a new geodetic-based Probabilistic Fault Displacement Hazard Analysis (PFDHA) approach constrained by measurements of near-field deformation of several past, large magnitude (M_w > 7) from correlation of optical and radar amplitude images. The near-field surface disparity maps allow us to characterize several important properties that affect the attenuation of inelastic strain away from the primary surface rupture including the effect of rock type, sediment thickness and degree of fault-zone compression and extension. The 2D displacement maps allow us to calculate the strain tensor from which we can identify rupture segments that underwent horizontal dilation or compression. For segments of the 2019 Ridgecrest surface rupture, we find clear examples of wider zones of inelastic strain in regions of transtension, indicating the degree of extension is an important parameter that needs be considered in PFDHA. An empirical geodetic-based PFDHA method has the potential to reduce the epistemic uncertainty in current probabilistic models of distributed rupture, ultimately providing more precise hazard information to engineers to design more resilient infrastructure that cannot avoid crossing faults (such as, gas and water pipelines, communications and roads) and help place empirical uncertainties on geologic slip rates that are an important input for Probabilistic Seismic Hazard Assessment.

Presenting Author: Christopher W. D. Milliner

Authors