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Monitoring crustal deformation along the Xianshuihe fault in the eastern Tibetan margin area with ENVISAT ScanSAR interferometry

Liming JIANG(1), Hui LIN(1), Fang LIU(2) and Qing ZHAO(1)

(1) Institute of Space and Earth Information Science, RM615, ELB, Chinese University of Hong Kong, Hong Kong, China
(2) Seismological Bureau of Sichuan Province, Seismological Bureau of Sichuan Province, Chengdu, 610041, China

Abstract

The Xianshuihe fault of Sichuan province, southwest China, is a highly active strike-slip fault approximately 350 km long. The fault is located in the eastern margin area of the Tibetan plateau, and is a part of a larger-scale fault system whose slip motion releases strain that plays a key role in collision of the Indian and Eurasian plates. It maybe ranked as one of the world’s most active faults, having produced sixteen earthquakes of M ≥ 6.5 since 1700. Previous studies have described up to 10-17mm/a of left-lateral slip on the Xianshuihe fault during the last decades, as indicated from geological criteria and GPS observations. The satellite InSAR observation is an alternative technique effectively used to measure the crustal deformation of the Xianshuihe fault, since the lack of vegetation in this area allows a coherent signal, even in a long-interval interferogram. However, the ENVISAT ASAR Image Mode (IM) imagery covers a 100 km wide stripe and will therefore not be sufficient for such large-scale deformation study.

In this work, we have applied the enhanced method called Scan Synthetic Aperture Radar (ScanSAR) interferometry technique to measure active crustal deformation along the Xianshuihe fault. The ENVISAR ASAR Wide-Swath SLC (WSS) data that cover in generally an area of 400×400 km2 were used for this study. A selected six of phase-preserving ASAR WSS data were processed by using the GAMMA DIFF/GEO module. Specific processing steps of ScanSAR interferometry include: (1) refined coregistration using SRTM3 DEM, (2) common band filtering in range and azimuth, (3)burst interferograms generation aggregation, (3) subtraction of the simulated phase based on SRTM3 DEM, (4)full swath recomposition and mosaicking, and (5) terrain geocoding. Especially, an interferogram stacking analysis was performed to reduce the effect of atmospheric distortion on deformation estimation.

The crustal deformation rate of the Xianshuihe fault between year 2003 and 2007 was estimated by using ENVISAT ScanSAR interferometry. Preliminary results were compared to InSAR observations based on “normal” ASAR IM imagery and GPS measurement. The deformation spatial distribution between them showed a good agreement that demonstrates the potential to monitor such wide-stretched deformation using ENVISAT WSS data.

 

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry