SCEC2021 Plenary Talk, Tectonic Geodesy

Mapping faults from space with InSAR: Ridgecrest and beyond

Xiaohua Xu, David T. Sandwell, Lauren A. Ward, Chris Milliner, Bridget R. Smith-Konter, Peng Fang, & Yehuda Bock

Oral Presentation

2021 SCEC Annual Meeting, SCEC Contribution #11112 VIEW PDF
One of the most important objectives in tectonic geodesy is to estimate the magnitude of off-fault deformation, which relies heavily on an understanding of how strain is distributed in the crust and the ability to precisely detect mm-scale deformation over broad regions of active faulting. Satellite radar observations were able to reveal hundreds of previously unmapped linear strain concentrations (or fractures) surrounding the 2019 Ridgecrest earthquake sequence. One interesting finding from these observations is that, although many fractures are displaced in the direction of the prevailing tectonic stress, a significant number of them are displaced in the opposite (retrograde) direction. Later analysis proved that (1) these fractures were largely driven by the static stress release of the nearby earthquake sequence, (2)the prograding fractures are likely formed from real slip, either due to new failure or on-fault motion, and (3) the retrograding fractures are a result of elastic compliant fault motion, which requires pre-existing faults with damage zones. A major implication from these results is that much of the shallow tectonic strain is accommodated by frictional slip on many pre-existing faults. Beyond this analysis, we further document the widths of the damage zones for the retrograding fractures to explore the possible parameters of these faults, such as historic offsets, fault depths, degree of material compliance, etc. This approach provides a method to map faults from space that are unclear in field surveys and a means to better understand their mechanics. Applications could be made to a number of recent cases.