InSAR observations of accelerated shallow creep on California faults

Ekaterina Tymofyeyeva

Published August 15, 2020, SCEC Contribution #10771, 2020 SCEC Annual Meeting Talk on TBD

Advances in InSAR data acquisition allow the modern satellite missions to make surface displacement measurements at high spatial resolution and frequent repeat times in areas where data from other geodetic instruments may be sparse or unavailable. Thanks to these capabilities, InSAR allows for observations of transient and secular deformation in locations where it would not be detectable using other methods.

A number of active continental strike-slip faults are associated with shallow creep, while other faults (or other sections of the same fault) appear to be locked all the way to the surface over the interseismic period. Traditional interpretations predict that shallow creep should occur at a quasi-constant rate throughout much of the earthquake cycle. However, geodetic observations indicate that faults that exhibit shallow creep can also host episodic accelerated creep events, similar to the episodic slow slip in subduction zones. These events can occur spontaneously or be triggered by static or dynamic stress changes due to nearby or distant earthquakes. Because surface displacements due to shallow fault creep are highly localized near the fault trace, observations of these events require dense spatial coverage and high temporal sampling. I will present observations from the Sentinel-1 mission, focusing on two case studies of recent shallow slip events on California faults. First, I will discuss the southern San Andreas fault, where an accelerated shallow creep event was triggered by the 2017 Mw 8.2 Chiapas (Mexico) earthquake, which occurred about 3000km away. I will also show a 2017 event on the Concord fault, in the Eastern Bay area, which appears to have occurred spontaneously. High-resolution measurements of displacements resulting from both events provide constraints on the localization of the shear zone, variations in slip magnitude along the strike of the fault, and fault geometry.

Citation
Tymofyeyeva, E. (2020, 08). InSAR observations of accelerated shallow creep on California faults. Oral Presentation at 2020 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy