SCEC Award Number 20016 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Postseismic deformation of the 2019 Ridgecrest earthquakes and its impact on the CGM
Name Organization
Roland B├╝rgmann University of California, Berkeley Kang Wang University of California, Berkeley Eric Fielding National Aeronautics and Space Administration Zhen Liu National Aeronautics and Space Administration
Other Participants
SCEC Priorities 1e, 3a, 3b SCEC Groups Geodesy, SDOT, CXM
Report Due Date 03/15/2021 Date Report Submitted 03/12/2021
Project Abstract
The primary goal of this project is to quantify the postseismic deformation in the first year following the 2019 Ridgecrest earthquake sequence and constrain postseismic relaxation models of this earthquake sequence. This information can eventually be used to correct for the postseismic transients of the 2019 Ridgecrest earthquake sequence when trying to characterize interseismic strain, which is one of the primary interests of the SCEC Community Geodetic Model (CGM). In the first year of this project, we have collected data from the Sentinel-1 and Cosmo-SkyMed (CSK) Synthetic Aperture Radar (SAR) missions and GNSS measurements to derive the postseismic deformation time series spanning ~1 year after the mainshock. The observed surface deformation reveals complex relaxation mechanisms following the 2019 Ridgecrest earthquake. Specifically, near-field InSAR LOS displacements from different looking directions constrain an afterslip model with most slip being concentrated at a relatively shallow depth around the mainshock hypocenter, while the far-field GNSS displacements are best explained by viscoelastic relaxation in the lower crust and upper mantle. In addition, clear evidence of poroelastic relaxation is found near complexities in the fault geometry and around the rupture tips. We show that the surface displacement time series in the area where postseismic relaxation is dominated by poroelastic rebound can be used to probe the in-situ hydrological properties (e.g. hydraulic diffusivity) of the fault zone.
Intellectual Merit This project characterizes the postseismic deformation following the 2019 Ridgecrest earthquake sequence, which directly contributes to establishing the Community Geodetic Model and crustal deformation in southern California. Postseismic deformation measurements derived from this effort provide essential constraints on the fault zone rheology, including the frictional properties of the fault plane, the effective viscosity of the lower crust and/or upper mantle, as well as the hydrological diffusivity of the near-fault crust and fault-zone rocks. The InSAR LOS velocity and displacement time series developed in this study complement the contributions of several other CGM groups focusing on the C-band Sentinel-1 InSAR data. The development of atmospheric noise correction methods in this study is also helpful to better utilize and interpret the InSAR data from various missions, such as the Sentinel-1, ALOS-2 and the planned NISAR mission.
Broader Impacts This project supported the intellectual development of a postdoc Kang Wang. Kang was supported to present his work at the 2020 SCEC meeting and interact with other members of the SCEC community. A research article summarizing the effort of this project is currently under preparation. The InSAR and GNSS velocity and displacement time series developed in this study will be integrated as part of the Community Geodetic Model, which will benefit a broader community.
Exemplary Figure Figure 2. Distribution of cumulative afterslip 0.9 years after the mainshock. Grey dots in panels to the right represent the aftershocks during ~2 weeks after the mainshock (Shelly, 2019). Blue contours represent the coseismic slip contours at 1 meter interval (from Wang et al., 2020). Red star represents the hypocenter of the mainshock. Green star denotes the approximate location of the Mw 5.5 aftershock on 06/30/2020.