Abstract
A rupture in the Chelungpu fault caused an Mw 7.6 earthquake on 21 September 1999 near Chi-Chi in central Taiwan. This earthquake was the most destructive experienced in Taiwan for the past century along this fault. In this study, we examined the earthquake-induced surface deformation pattern using differential synthetic aperture radar interferometry (D-InSAR) combined with global positioning system (GPS) data regarding the footwall of the Chelungpu fault. Six synthetic aperture radar (SAR) scenes, approximately 100×100 km each, recorded by the European Remote Sensing Satellite 2 (ERS-2), spanning the rupture area, were selected for study. The data were used to generate a high-resolution, wide-area map of displacements in flat or semi-flat areas. Interferograms show radar line contours indicating line-of-sight (LOS) changes corresponding to surface displacements caused by earthquake ruptures. These results were compared to synthetic interferograms generated from GPS data. Displacements shown by GPS data were interpolated onto wide-area maps and transformed to coincide with the radar LOS direction. The resulting coseismic displacement contour map showed a lobed pattern consistent with the precise GPS based displacement field. Highly accurate vertical displacement was determined using D-InSAR data using the coordinate transform method, while GPS data was effective in showing the horizontal component. Thus, this study confirmed the effectiveness of the D-InSAR method for determining the coseismic deformation caused by the Chi-Chi earthquake at the footwall of the Chelungpu fault.
Highlights
Synthetic Aperture Radar Interferometry combines complex images recorded by antennas at different locations or at different times
The European Remote Sensing Satellite 2 (ERS-2) C-band synthetic aperture radar (SAR) with 35-day repeat cycle produced six images covering the earthquake area close to 21 September 1999; these images were recorded on 6 May, 10 June, 15 July, 19 August, 23 September, and 28 October 1999
D-InSAR was used to detect surface deformation caused by the Chi-Chi earthquake
Summary
Synthetic Aperture Radar Interferometry combines complex images recorded by antennas at different locations or at different times. The resulting interferograms permit the determination of differences in the range direction This technique has been used widely to produce highly accurate digital elevation model (DEM) and topographic maps (Zebker and Goldstein 1986; Madsen et al 1993) and to measure displacement fields or terrain motions (Massonnet et al 1993; Zebker et al 1994). D-InSAR and its spatially dense, accurate deformation measurements have advanced studies of the Earth’s crust This technique provides a comprehensive view of detectable motion for the entire area affected. Results from such analyses can supplement ground-based measurements taken at a limited number of locations. The great advantage of the radar interferometer system is that it allows deformation measurements at very fine spatial spacings, creating a visual image of the deformation distribution (Zebker 2000)
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