Rapid-response GPS following the 2019 Ridgecrest Earthquake Sequence
Abstract
In response to the M6.4 July 4 Ridgecrest earthquake the USGS mobilized a rapid geodetic ground response comprising installation or reoccupation of 22 GPS sites. The response focused on the access-limited Naval Air Weapons Station China Lake (NAWSCL). On the evening of July 4th, we installed two GPS sites straddling the surface rupture crossing Highway 178 (RCRW&RCRE). Over the next several days we reoccupied another 6 sites distributed around the region that had been surveyed by the USGS for the past two decades. Of these, RCRW and RCRE, at an orthogonal distance of ~3.5km SW of the surface rupture, recorded the largest co-seismic GPS displacements for the M7.1 July 19 event (~ 75cm) that occurred at 20:19 local time. Roughly 1.5 hours after the M7.1 event, we installed two stations straddling its surface rupture crossing Highway 178. On July 6th at the M7.1 epicenter and ~ 5.5 km south of it, we installed another 2 pairs of fault-straddling stations and occupied a preexisting campaign site ~ 3.3 km orthogonal distance NE of the surface rupture. Subsequently, from July 26-29, for monitoring continued near- and intermediate-field post-seismic deformation, we installed an additional 9 sites closer than 10 km and 1 site ~ 15 km from the rupture trace. Near-field siting was aided by examination of Sentinel 1-A ascending and descending post-seismic interferograms and field-mapping that identified potential areas of rapid transient deformation associated with fault splays and step-overs. Preliminary processing suggests that shallow afterslip (< 500 meters depth) is likely minimal although slightly longer wavelength (few kms) deformation signals suggest deeper afterslip and/or poroelastic rebound effects. All CGPS and SGPS data were processed within one day of collection. Once they are cleared by NAWSCL as part of the overarching USGS on-base data collection effort, they will be archived for public access at UNAVCO.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.S31F0469S
- Keywords:
-
- 7299 General or miscellaneous;
- SEISMOLOGY