Using the feature matching technique to reveal the displacement of a non-catastrophic landslide induced by the Mw 7.6 Chi-Chi earthquake in central Taiwan

The Chi-Chi earthquake occurred in 1999 in the western of central Taiwan, and caused several catastrophic landslides The Hongtsaiping area in central Taiwan was reported to have several meters of slide in a small scale area. The reported landslide is unlike to a catastrophic event. To better understand the characteristics of such non-catastrophic and unobvious landslide, this study tries to characterize the sliding directions, their magnitudes and region of the landslide. Three set of orthorectified aerial photographs of the Hongtsaiping area were used, which were taken in 1998/06/13, 1999/11/18 and 2002/10/26. Using the Particle Image Velocimetry (PIV), Scale Invariant Feature Transform (SIFT) and Affine Scale Invariant Feature Transform (ASIFT) feature matching techniques, the displacement of the landslide were calculated. Based on the results of the feature matching analysis, the slide direction, their magnitudes and region of the landslide were estimated. The matching results show that the maximum horizontal displacement caused by the earthquake is about 24 m towards NW between 1998 and 1999. The result indicates that after the Chi-Chi earthquake, the non-catastrophic landslide did not occur again between 1999 and 2002. ASIFT has much more known matching points than other techniques. Compared to the traditional method of monitoring landslides, the cost is small and can quickly achieve effective results.