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How Stressed Out Are Faults? Estimating Co-Seismic Stress Using Measurements of 3D Surface Deformation With Optical Image Correlation

Session: Crustal Stress and Strain and Implications for Fault Interaction and Slip II

Type: Oral

Date: 4/22/2021

Presentation Time: 02:00 PM Pacific

Description: 

Constraining the variation of stress throughout the crust and over time has importance for improving our understanding of the mechanics of faulting. However, estimating the orientation and amplitude of the stress state that drives coseismic fault slip is highly challenging, as slickenlines and offset geomorphic features, which are the only approach that can quantify the full coseismic slip vector, are either rare or spatially limited along ruptures. Here we use geodetic imaging based on multi-temporal and multi-sensor stereo-optical imagery to measure the full 3D coseismic surface deformation pattern in high spatial detail (at meter scale pixel resolution with decimeter accuracy) that can measure the full slip vector. Using this technique, we measure the 3D surface deformation and coseismic slip vectors every ~100 m along a number of surface rupturing, continental oblique strike-slip earthquakes including, the 2010 M_w 7.2 El-Mayor Cucapah, 2016 M_w 7.1 Kumamoto, 2016 M_w 7.8 Kaikoura and 2019 M_w 7.3 Ridgecrest earthquakes. From the coseismic surface slip vector data we then invert for the coseismic 3D stress tensor in a manner similar to that of inverting focal mechanisms to estimate the interseismic and postseismic stress orientations. With estimates of the co-seismic stress state for a number of surface rupturing events we will discuss how the strength of faults varies as a function of structural maturity, whether the stress orientation is spatially homogenous or varies significantly along the rupture length, whether stresses rotate from the far-field towards the fault-zone and if there are any significant temporal changes of stress between the inter-, co- and post-seismic periods.

Presenting Author: Christopher W. D. Milliner

Student Presenter: No

Authors