How is Coseismic Strain Released across Damage Zones and with Depth? Insights using Sub-pixel Optical Image Correlation

Chris Milliner

UC Berkeley

Date & Time
Building 3, Rambo Auditorium
Josie Nevitt

Surface deformation from large magnitude earthquakes provide vital insight into faulting mechanics and the rupture process at depth. However, our understanding of the surface deformation close to fault ruptures (< 2 km) remains limited. GPS data are commonly too sparse to capture complex surface motion, while Interferometric Synthetic Aperture Radar (InSAR) typically decorrelates in such regions due to high phase gradients, and traditional field surveys usually cannot constrain diffuse, off-fault deformation. Sub-pixel correlation of optical images taken before and after earthquakes, however, is well optimized to retrieve the full surface displacement close to the earthquake rupture, providing a complementary technique to other geodetic methods. In this talk I will present optical correlation results that reveal the near-field deformation pattern of the 1992 Mw 7.3 Landers and 1999 Mw 7.1 Hector Mine earthquakes in high spatial resolution. I will demonstrate how such measurements can deepen our understanding of fault zone deformation, from how the magnitude of distributed, inelastic strain may vary between fault systems to how fault slip is distributed with depth. These results have important implications for understanding the dynamics of rupture, diffuse deformation in continental regions, and reliably estimating geologic slip rates for our understanding of plate kinematics.

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