SCEC Award Number 19042 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title ALOS-2 InSAR Component for SCEC Community Geodetic Model
Investigator(s)
Name Organization
Roland Bürgmann University of California, Berkeley Paul Lundgren National Aeronautics and Space Administration
Other Participants Kang Wang, UC Berkeley postdoc
SCEC Priorities 1a, 2a, 3e SCEC Groups Geodesy
Report Due Date 03/15/2020 Date Report Submitted 03/31/2020
Project Abstract
 The primary goal of this project is to provide optimal InSAR data products from the ALOS-2 system for integration into the SCEC Community Geodetic Model (CGM) to characterize surface deformation in Southern California at the highest possible spatio-temporal resolution and accuracy. In this project, we analyze L-band ALOS-2 SAR data acquired from early 2015 to 2019 to derive interseismic velocity maps and time series over southern and central California. The InSAR processing is based on the processing flow of Liang et al., (2018). Using 24 scenes acquired from early 2015 to 2019 along the descending track D165 using ISCE, we generated 70 interferograms with high radar coherence and robust corrections for the ionospheric noises. One of the most significant limitations to InSAR measurements of a low-amplitude deformation, such as the interseismic deformation, is the variability of water vapor in the atmosphere. In this study, we developed a new method by combining the ERA-5 weather model with the Common-Scene-Stacking (CSS) to correct for tropospheric delays. We find that both the average velocity and time series match the GPS observations much more closely when the above mentioned atmospheric corrections are applied. Data derived in this study will complement the Sentinel-1 and GPS observations for developing a more complete and robust CGM over southern California.
Intellectual Merit This project directly contributes to establishing the Community Geodetic Model and helps characterize the crustal deformation kinematics in southern California. The ALOS-2 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 noises correction methods in this study is also helpful to better utilize and interpret the InSAR data from other missions, such as the Sentinel-1 and the planned NISAR.
Broader Impacts This project supported the intellectual development of a postdoc Kang Wang. Kang was supported to present his work at the 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 ALOS-2 InSAR 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 of earthquake hazard researchers.
Exemplary Figure Figure 3.
Comparison of average velocity between GPS and ALOS-2 observations. (a) color represents the ALOS-2 LOS velocity derived from SBAS analysis after ionospheric and tropospheric noise correction. Negative values correspond to ground motion away from the satellite. Black vectors are GPS velocities in the IGS14 reference frame, with the site P617 pinned to zero. (b) and (c) show the LOS velocities along a profile A-A’ shown in (a) before and after corrections for the atmospheric noises, respectively. Note that the velocity profile without atmospheric noise correction exhibits strong oscillations from -50 to 50 km distance, and significantly deviates from the GPS observations (red circles). The GPS data were not used in deriving the InSAR velocity field.
Figure credit: Kang Wang