Geodetic and geologic observations of creep on the Southern San Andreas Fault triggered by the 2017 Chiapas (Mexico) earthquake

Ekaterina Tymofyeyeva, Yuri Fialko, Junle Jiang, Roger Bilham, David T. Sandwell, Thomas K. Rockwell, Chelsea M. Blanton, & Allen M. Gontz

Published August 14, 2018, SCEC Contribution #8597, 2018 SCEC Annual Meeting Poster #114

Observations of shallow fault creep reveal increasingly complex time-dependent slip histories that include quasi-steady creep and triggered as well as spontaneous accelerated slip events. We report a recent slow slip event on the southern San Andreas fault (SSAF) triggered by the 2017 Mw 8.2 Chiapas (Mexico) earthquake that occurred approximately 3000 km away. Geodetic and geologic measurements indicate that 4-12 mm of surface slip that occurred on a 40-km-long section of the SSAF between the Mecca Hills and Bombay Beach over 6 months following the Chiapas earthquake. Both the magnitude and the depth extent of creep vary along strike. We derive a high-resolution map of surface displacements by combining Sentinel-1 Interferometric Synthetic Aperture (InSAR) acquisitions from different lines of sight. InSAR-derived displacements are in good agreement with the creepmeter data and field mapping of surface offsets. In addition, we calculate InSAR time series at selected locations along the fault. Although InSAR acquisitions are too infrequent to pinpoint the exact timing of the event, we are able to capture the temporal history of the transient surface deformation due to triggered creep. Inversions of surface displacement data using dislocation models indicate that the highest amplitudes of surface slip are associated with shallow (<1 km) depth extent of transient slip.

Citation
Tymofyeyeva, E., Fialko, Y., Jiang, J., Bilham, R., Sandwell, D. T., Rockwell, T. K., Blanton, C. M., & Gontz, A. M. (2018, 08). Geodetic and geologic observations of creep on the Southern San Andreas Fault triggered by the 2017 Chiapas (Mexico) earthquake. Poster Presentation at 2018 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy