Rupture models of the 2019 M6.4-7.1 Ridgecrest earthquakes constrained by space geodetic data and aftershock locations

Zeyu Jin, & Yuri Fialko

Submitted August 14, 2019, SCEC Contribution #9683, 2019 SCEC Annual Meeting Poster #275 (PDF)

Poster Image: 
The July 2019 Ridgecrest earthquake sequence includes two major events, the M6.4 foreshock and M7.1 main shock that ruptured the nearly orthogonal intersecting strike-slip faults within one day of each other. Analysis of space geodetic observations including InSAR data from Sentinel-1A/B and ALOS-2, and field mapping reveals a complex pattern of surface rupture with several sub-parallel fault strands with moderate variations in strike. The precisely relocated aftershock catalog (courtesy of E. Hauksson, Caltech) suggests a smaller variability in the rupture strike at the seismogenic depths. Because the resolution of geodetic inversions is decreasing with depth, we use the precisely located aftershocks to constrain the fault geometry below the depth of 3 km. The near surface fault geometry is defined by surface offsets derived from the space geodetic data and the assumption of rupture continuity as a function of depth. The resulting fault geometry indicates a significant near-surface complexity around the epicentral area involving variations in both strike and dip of the seismic rupture. We performed joint inversions of surface displacement data, including line of sight displacements from Sentinel-1 and ALOS-2, pixel tracking, GPS data, and fault geometry constrained by the aftershock and surface offsets to estimate the sub-surface slip distribution. Inversions are performed for both homogeneous and layered elastic half-space with elastic moduli derived from a local 1-D seismic velocity model. The seismic moments predicted by the finite slip models for each event are in good agreement with values reported in seismic catalogs. The along-strike averaged slip distribution suggests a moderate shallow slip deficit consistent with models of the dynamically triggered off-fault damage (Kaneko and Fialko, 2011). We also present 3-components models of co-seismic surface displacements derived from space geodetic data from various view geometries. The coseismic rupture model and slip distribution will be used in studies of time-dependent postseismic response of the July 2019 sequence.

Citation
Jin, Z., & Fialko, Y. (2019, 08). Rupture models of the 2019 M6.4-7.1 Ridgecrest earthquakes constrained by space geodetic data and aftershock locations. Poster Presentation at 2019 SCEC Annual Meeting.


Related Projects & Working Groups
Ridgecrest Earthquakes