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Measurement of Interseismic Strain Accumulation and Post-seismic Relaxation along the Kunlun Fault by Radar Interferometry

Jianbao Sun(1), Xiwei Xu(2), Zhengkang Shen(2) and C├ęcile Lasserre(3)

(1) Graduate University of Chinese Academy of Sciences, Yuquan Rd 19A, Beijing, 100049, China
(2) China Earthquake Administration, PO Box 9803, 100029, China
(3) ENS, Paris, 24, rue Lhomond, Paris, 75231, France

Abstract

SAR interferometric technique shows great potential in detecting small tectonic signals in recent years. In this study, we mainly measure both of the interseismic deformation and post-seismic deformation across the Kunlun fault by multi-temporal INSAR methods using archived and planned ERS and ASAR radar data. This fault is one of the major left-lateral strike-slip systems in the northern Tibet. Two large earthquakes (Mw7.5 and Mw7.8) happened on its western end and middle part (namely the Mani segment and the Ku Saihu segment) in 1997 and 2001 respectively. In order to better constrain the present mechanical behavior of this fault system and investigate its stress field evolution, we use SAR interferometry to detect interseismic signals of these segments, which highlights the strain accumulation before the two important events. Many researches had also inverted the co-seismic radar data of them (Peltzer, 1999; Sun, 2007; Gareth, 2007; Lasserre, 2006). In the earthquake cycles, we also need to analysis the post-seismic activity of the earthquakes, so that we can better understand the rheology characteristics of this area and earthquake stress field evolution. Along the Mani segment, we processed 3 track ERS data before Nov. 1997, when the Mani earthquake happened. The data show good coherence across the fault, so that we can easily connect phase between the 2 sides of the fault. We use the simple data stacking technique with low atmospheric delay INSAR pairs. For comparison purpose, we also process the data with SBAS method. Preliminary results show ~ 10mm/yr slip rate of the segment with 18 km locking depth, which is consistent with our co-seismic inversion. Along the Dongdatan-Xidatan segment, we processed all of the ERS data along track 090, which show better correlation than the other 2 neighbor tracks. If we use the locking depth 18km as inverted by Laserre,2006, the inverted slip rate along this seismic gap would be 7~8 mm/yr. For the post-seismic of Kokoxili earthquake, we use INSAR data only after 2003 because there is no suitable ERS data for the time interval between the end of 2001 and 2007. In this interval we mainly use the SBAS technique to extract the time-series deformation with ASAR data. Because it had already been 2 years after the quake, we mainly model the deformation with relaxation models. The GPS data was also used in this study.

 

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