Deformation of 921 Earthquake by Satellite Radar Interferometry: Co-seismic and Post-seismic Estimation

摘要

A major earthquake ( M_L =7.3 ) has occurred near the small town Chi-Chi in the Nantou County, Taiwan, at 1:47 a.m. local time on September 21, 1999 ( 17:47 GMT on 20 September). The epicenter was 12.5 km northwest the Sun-Moon lake. The focal depth is 8 km. The death toll has exceeded 2100 and is mounting during the first week after the main shock. In this study, we mainly focus on the there are numerous aftershocks; some of which reach magnitudes of M_L= 6.8. In this paper we used 8 scenes (1998/01/01, 1999/01/21, 1999/05/06, 1999/06/10, 1999/07/15, 1999/09/23, 1999/10/28, 2000/01/06) of ERS2 images and an external DTM data, by the means of two passes SAR differential interferometry, to detect the deformations before and after the Chi-Chi earthquake. The results based on the available image sets show that prior to the earthquake, it has no clear deformation signature in the interferogram and there are slight displacements in the east of Chelungpu fau and the displacement areas of the two pairs of DINSAR (1999/10/28 ― 1999/09/23; 2000/01/06 ― 1999/10/28 ) were at the same place. The former had about 5.6 cm deformation in slant range, while the latter was about 3 cm. These post-seismic deformations may be due to gravity effects, or the theory of elastic rebound.