SAR Imaging of the Coseismic and Postseismic Deformation From the 2019 M7.1 and M6.4 Ridgecrest Earthquakes in California

Session: Observations From the 2019 Ridgecrest Earthquake Sequence
Type: Oral
Date: 4/28/2020
Time: 02:45 PM
Room: 115
Description: 

We analyzed synthetic aperture radar (SAR) images from Copernicus Sentinel-1A and -1B satellites operated by the European Space Agency and the Advanced Land Observation Satellite-2 (ALOS-2) satellite operated by Japanese Aerospace Exploration Agency for the 4 July 2019 M_w 6.4 and 5 July M_w 7.1 Ridgecrest Earthquakes. We integrate geodetic measurements for the three-dimensional vector field of coseismic surface deformation for the two events and measure the early postseismic deformation, using SAR data from Sentinel-1 and ALOS-2 satellites. We combine less precise large-scale displacements from SAR images by pixel offset tracking or matching, including the along-track component, with the more precise SAR interferometry (InSAR) measurements in the radar line-of-sight direction and intermediate-precision along-track InSAR to estimate all three components of the surface displacement for the two events together. InSAR coherence and coherence change maps the surface disruptions due to fault ruptures reaching the surface. The combined measurements reveal large-scale deformation due to slip at depth and near-fault deformation. The NW-striking fault that was the main rupture in the Mw 7.1 earthquake has variations on the amount of slip reaching the surface. The Garlock fault had triggered slip of about 15 mm along a short section directly south of the main rupture. About 3 km NW of the Mw 7.1 epicenter, the surface fault separates into two strands that form a pull-apart with about 1 meter of down-drop.

We image postseismic deformation with InSAR data. Initial analysis of the first four months InSAR measurements indicates the pull-apart continued dropping. The main fault had substantial afterslip close to the epicenter just north of where the largest coseismic slip occurred. Sentinel-1 6-day repeats enable postseismic time-series analysis to reduce atmospheric effects. Slip on a NE-striking fault near the northern end of the main rupture in the first weeks, in the same zone as large and numerous aftershocks along NE-striking and NW-striking trends shows complex deformation.

Presenting Author: Eric J. Fielding

Authors