Complementing CGM with surface deformation measurements from dense catalogs of SAR data

Ekaterina Tymofyeyeva, & Yuri Fialko

Published August 13, 2019, SCEC Contribution #9517, 2019 SCEC Annual Meeting Poster #320

The SCEC Community Geodetic Model (CGM) aims to describe surface deformation in Southern California at highest possible spatio-temporal resolution and accuracy. This requires an optimal integration of GPS and InSAR (Interferometric Synthetic Apreture Radar) data. Over the last five years, there has been a dramatic increase in the amount of InSAR data thanks to the current satellite missions such as Sentinel-1 (European Space Agency) and ALOS-2 (Japanese Space Agency).

Propagation artifacts (e.g., due to variability in the water content in the troposhere, or the electron content in the ionosphere) are the main limitations to measurements of small-amplitude long-wavelength surface displacements. Large volumes of InSAR acquisitions are expected to mitigate the problem of propagation artifacts by statistical averaging of the atmospheric/ionospheric contributions to the radar phase, resulting in an improved signal to noise ratio. However, an increasing number of radar interferograms used in the analysis of surface deformation is found to result in the accumulation of a high-frequency spatial noise. Such noise is introduced in the time series analysis due to filtering of the radar phase prior to phase unwrapping. We demonstrate this using the circuit closure test, i.e. computing the difference between the sum of the phase from sequential interferograms, and a direct interferogram spanning the entire time period between the first and last acquisitions. The circuit non-closure errors accumulate progressively as more interferograms are added. The same test using unfiltered wrapped interferograms yields a much better circuit closure. It is therefore desirable to avoid filtering of the radar phase in order to improve the accuracy of the InSAR time series. We propose a method for "unfiltering" the filtered unwrapped radar phase. We demonstrate the feasibility of the proposed method using Sentinel-1 InSAR and Global Positioning System (GPS) data from Southern California.

Citation
Tymofyeyeva, E., & Fialko, Y. (2019, 08). Complementing CGM with surface deformation measurements from dense catalogs of SAR data. Poster Presentation at 2019 SCEC Annual Meeting.

Related Projects & Working Groups
SCEC Community Models (CXM)