SCEC2021 Plenary Talk, Tectonic Geodesy

Characterizing the Deformation and Hazard of Fault Zones Using Geodetic Imaging Data

Chris Milliner, Jean-Philippe Avouac, Saif Aati, Rui Chen, Brian Chiou, Timothy Dawson, Andrea Donnellan, & James F. Dolan

Oral Presentation

2021 SCEC Annual Meeting, SCEC Contribution #11135
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 have unknown uncertainty and are typically spatially sparse along and across ruptures. Here we present a new geodetic-based PFDHA approach that is constrained using optical image correlation data of several past, large magnitude earthquakes (Mw > 7) that can resolve the full coseismic near-field deformation pattern. We will show results following an adaptation of the optical image correlation approach where we have implemented a ray-tracing approach that can now measure the full 3D surface deformation field using imagery acquired from different satellite sensors and viewing geometries. This gives the advantage of a larger number of available look vectors with which to constrain the 3D position and translation of pixels with time. Estimating the finite strain tensor from the 3D surface displacements maps allows us to assess the effect of several physical properties on the attenuation of inelastic deformation away from the primary surface rupture including rock type, sediment thickness, and amount of fault-zone compression and extension. For instance, along the 2019 Ridgecrest surface rupture, we find clear examples of wider zones of inelastic deformation in rupture segments that experience transtensional strain, indicating the type of fault geometry is an important parameter that should be considered in fault displacement prediction equations. An empirical geodetic-based PFDHA method constrained by data with known uncertainties and complete measurement of the spatial distribution of coseismic deformation has the potential to reduce the epistemic uncertainty of current probabilistic models of distributed rupture. This will ultimately provide more precise fault displacement hazard estimates that will aid engineers in designing more resilient infrastructure and place empirical uncertainties on geologic slip rates that are an important input for probabilistic seismic hazard assessment.