SCEC Award Number 22069 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Geodetic investigation of transient deformation following the 2019 Ridgecrest earthquake sequence in southern California
Investigator(s)
Name Organization
Eric Fielding National Aeronautics and Space Administration Roland Bürgmann University of California, Berkeley Zhen Liu National Aeronautics and Space Administration Kang Wang University of California, Berkeley
Other Participants
SCEC Priorities 2c, 3a, 3f SCEC Groups Geodesy, CXM, SDOT
Report Due Date 03/15/2023 Date Report Submitted 03/21/2023
Project Abstract
 This project extends our previous effort in quantifying the spatial and temporal distribution of postseismic deformation following the 2019 Ridgecrest earthquake sequence. We show that all three commonly considered mechanisms, i.e.,afterslip, viscoelastic relaxation and poroelastic rebound contributed to postseismic relaxation ~3.2 years after the 2019 mainshock. Specifically, the horizontal displacements in the near-to-medium field revealed by both InSAR and GNSS are dominantly controlled by afterslip that mainly occurs at the bottom of the coseismic rupture and in areas of the relatively low coseismic slip. The vertical deformation found mainly near the rupture tips and fault geometry complexities, on the other hand, is best explained by poroelastic rebound of the shallow crust. Lastly, GNSS displacements in the far field (>100 km from the mainshock epicenter) is qualitatively consistent with model predictions of viscoelastic relaxation, and the observed far-field deformation is indicative of lateral variation in rheology across the epicentral area. The other objective of this project is to explore the feasibility of using Multi-Aperture Interferometry (MAI) of Synthetic Aperture Radar (SAR) to image the tectonic motion along the satellite’s flying direction. Our initial tests with ALOS-2 ScanSAR data acquired over the Ridgecrest earthquake area do not reveal a clear pattern of surface motion based on MAI, likely because of the strong ionospheric perturbation and small displacements expected from the postseismic relaxation. We are still exploring how the ionospheric correction, e.g., range split-spectrum method, can be implemented more accurately in the MAI processing flow.
Intellectual Merit This project characterizes the spatial and temporal distributions of postseismic deformation following the 2019 Ridgecrest earthquake sequence in southern California. It is tightly related to severall SCEC research priorities and objectives. First, postseismic deformation models derived in this effort are of great importance to sharpen our understanding of the stress evolution after a large earthquake, and constrain the rheological properties of the fault zone and surrounding rocks. Second, the InSAR LOS velocity and displacement time series developed in this study can directly contribute to the development of the time-dependent CGM going beyond Ridgecrest. The postseismic deformation models derived in this study can be also used to correct for the postseismic transients of the 2019 Ridgecrest earthquake, should the long-term interseismic rate become the main interest of future CGM development and application. Lastly, the methods of correcting for the InSAR atmospheric noise developed in this study are also helpful to better utilize and interpret the InSAR data of other SAR missions, such as the ALOS-2 and the planned NISAR mission.
Broader Impacts This project supported the intellectual development of two postdoc researchers, Dr. Kang Wang at UCB and Niloufar Abolfathian at JPL. The postseismic deformation data and models developed in this project will contribute to the development of the Community Geodetic Model, which is expected to benefit a broader research community.
Exemplary Figure Figure 2. Postseismic line-of-sight (LOS) displacements derived from Sentinel-1 InSAR using data from the ascending track ASC64 (a) and descending tracking DES71 (b). Panels (c) and (d) show example line-of-sight (LOS) time series obtained with different approaches of atmospheric noise correction. Note that the LOS time series without atmospheric correction exhibit large scattering and apparent annual variation with a period of roughly 1 year, which is likely due to the seasonal variation of the tropospheric delay, as the amplitudes of such seasonal variation are significantly reduced when applying an atmospheric correction with either the ERA-5 weather model or the GNSS-based Zenith Total Delay products. The effect of the Common-Scene-Stacking (CSS) (Tymofyeyeva and Fialko, 2015) mainly reduces the high-frequency noise, and it preserves the relatively long-term deformation trend.
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