SCEC Award Number 15108 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Recovering vertical and time-dependent deformation near Coachella Valley, California with InSAR
Investigator(s)
Name Organization
David Schmidt University of Washington Xiaopeng Tong University of Washington Andrew Barbour United States Geological Survey David Sandwell University of California, San Diego
Other Participants
SCEC Priorities 1d, 4a, 5b SCEC Groups Geodesy, SDOT, Transient Detection
Report Due Date 03/15/2016 Date Report Submitted 03/13/2016
Project Abstract
 This study focuses on analyzing the SAR data in Southern California with the goal of resolving the surface deformation found along the Southern San Andreas fault. We present a refined methodology for recovering the time-dependent deformation that enhances the signal in regions of low coherence. Our InSAR time-series method incorporates pixel coherence into the covariance matrix, which performs better than the traditional Small Baseline Subset (SBAS) method. We analyzed ERS, ENVISAT and ALOS-1 data over the Coachella Valley region with this coherence-based SBAS method. The InSAR maps show many interesting deformation signals including (1) post-seismic transient from 1992 Landers and 1999 Hector Mine earthquakes, (2) aquifer deformation near the San Andreas Fault and the San Jacinto Fault, (3) the compliant fault zone of the Pinto Mountain fault. These results provide higher resolution images of these geodetic signals. Anomalies in the vertical deformation field, at the southwestern edge of the Coachella Valley, can be explained by fluid extraction from a poroelastic half-space model. To reduce the atmospheric noise in the InSAR measurements, we propose a new way to determine an optimal temporal smoothing factor. The choice of the smoothing can be determined by investigating the empirical trade-off between the RMS reduction of the phase of the interferograms and the smoothing weight. The results are in good agreement with vertical GPS time-series.
Intellectual Merit This research helps to resolve the interseismic deformation across the plate boundary, which is directly related to the strain accumulation on regional faults. We further developed an important geodetic method for producing InSAR time-series. Tests on multiple InSAR dataset have shown the capability of this approach to retrieve surface deformation, especially in the vertical direction. This research advances our understanding of time-varying geodetic signals in Southern California especially in the vertical component. A reliable vertical displacement field can help us to develop both the time-dependent and time-independent component of the CGM.
Broader Impacts The funding of the project has supported a postdoc at University of Washington and his collaborations with scientists from the University of California San Diego and the USGS. The development of the InSAR time-series method is implemented in an open source InSAR processing system. The results of this research have been presented at the SCEC annual meeting.
Exemplary Figure Figure 3. a) InSAR mean velocity from ENVISAT (2003-2011) over the Coachella Valley in Southern California. b) Comparison between the relative displacement time-series of GPS and InSAR at sites COTD and sites PSAP. c) Similar comparison as b) at sites CACT and sites TMAP. d) The subsidence observed by InSAR near COTD (left), a model of fluid extraction from a poroelastic half-space (middle), and residual displacements (right). The best-fitting extraction rates and depths for the five sources along the profile (at the dashed lines) are found by Simulated Annealing. (Figure credits: X. Tong, A. Barbour, D. Schmidt, D. Sandwell).
Linked Publications

Add missing publication or edit citation shown. Enter the SCEC project ID to link publication.