Astudy On Coseismic Deformation Field Extracting By Using D-InSAR And Offset_Tracking Methods

Extracting the coseismic surface deformation field of earthquake has great significance for positioning the macro-epicenter, accessing the geometry and kinematics characteristics of earthquake fault, analysising and studying the strength and mechanism of deformation between the continental masses. At present, D-InSAR (Differential Interferometric Synthetic Aperture Radar) technique is generally used to extract coseismic deformation due to the advantage of space continuous coverage, all-weather, all-time, and high spatial resolution of SAR image. Offset_tracking technique is relatively immature for D-InSAR and less precise, but it has been made a successful application in Glaciers and some measurements of strike-slip earthquake deformation field, now that it is not sensitive to coherence of the SAR image, doesn't need to unwrap phase, can get the range and azimuth for two-dimensionnal deformation field. Thus, using D-InSAR and Offset_tracking methods simultaneously can complement each other while extracting the surface deformation field, which also can dectect the deformation characteristics of coseismic deformation field comprehensively.In this paper, taking the Bam earthquake, Wenchuan earthquake and Yushu earthquake as examples, we acquired the coseismic deformation fields by using D-InSAR and Offset_tracking methods, and analyzed the advantages and disadvantages of two methods. Major work is summarized as follows:1. we acquired coseismic deformation field of ascending orbit and descending orbit modes in different directions by D-InSAR technique and Offset_tracking technique with ASAR images. The results show that Bam earthquake has the characteristic of right-lateral striking in the north-south direction , with left-lateral horizontal rotation in the east-west direction.2. Using 112 view PALSAR images, we determined the coseismic deformation field of Wenchuan earthquake. The results indicate that the coverage area of whole deformation field is about 400×400km~2, it effects the region of the county of NanPing and Kang in the northward and the city of Emei, LeShan, SuiNing, ChongQing in the southward. Deformation field suggests that there are two surface rupture zones caused by this earthquake, such as Yingxiu-Beichuan main rupture zone which is about 250 ~ 260 km and Hanwang-Bailu secondary rapture zone which is about 60 km. According to the investigation, we can predict that the main rupture zone of Yingxiu-Beichuan has the characteristics of thrusting and right-lateral striking, the secondary rapture zone of Hanwang-Bailu has the characteristics of thrusting and left-lateral, so this earthquake has experienced a complex tectonic movement.3. We used 4 view PALSAR images to measure the coseismic deformation field of the Yushu earthquake in LOS direction based on D-InSAR, and converted the displacement along the fault direction by horizontal solution model. Then, the range and azimuth displacement were determined by Offset_tracking technique. The results show that the seismogenic fault Ganzi-Yushu fault is left-lateral strike-slip, main fracture area is nearby the village of GuoQing which has a strong surface deformation. The surface rupture length is about 60 km, and the epicenter is ( 96°5 0'56"E,33°0 3'29"N). The maximum relative dispalcement across the fault is about 182.3cm. The extension of the deformation field is about 10km. The displacement on both sides of fault is not symmetry, and the displacements of the southwest wall of the fault are obviously more than that of the northeast wall. This phenomenon may be caused by aftershocks which mostly occurred in the southwest.4. Obtained the advantages and disadvantages and primary applicability of two methods. In view of the the existing radar satellites, which are sun-synchronous orbit, we can conclude that D-InSAR has the advantages in extracting the deformation of east-west fault which is mainly strike-slip rupture and normal fault, the deformation of south-north fault which is mainly reverse fault and normal fault, and Offset_tracking has the advantage for east-west fault which is mainly thrust fault, for the south-north fault which is mainly strike-slip rupture.