Detection of urban disaster using InSAR. A case study for the 1999 Great Taiwan Earthquake

The authors studied the applicability of interferometric SAR (InSAR) using ERS-2 SAR data for detecting damaged urban areas by the Great Taiwan Earthquake (Chi-Chi Earthquake) occurred on Sep. 21, 1999. Three temporal ERS-2 SAR data acquired by Taiwan ground station on Jan. 21, May 6, and Sep. 23, in 1999 were used as the test data. By overlaying two SAR multi-look intensity images before (May 6) and after (Sep. 23) the earthquake, it was found that the damaged urban areas by the earthquake were hardly detected only by the intensity change. On the other hand, the overlay of the two coherence images from the pairs (Jan.-May) and (May-Sep.) indicated that the urban areas damaged severely (e.g. Dongshi) resulted in clear decrease of coherence by the earthquake occurrence, while the coherence in the urban areas not damaged severely (e.g. Taichung) did not change even after the earthquake. The result of this study suggests that InSAR technology has a great potential for detecting urban disasters by earthquake.