抄録
Many landslides occurred during the Chi-chi earthquake (ML=7.3) on 21 September 1999 in western central Taiwan. These land-slides have been discerned from either aerial photographs or SPOT images, digitized, and coregistered with topographic maps at 1: 25, 000 scale. The data of the landslides were manipulated using ArcView GIS. Results indicate that the rock formation consisting of sandstone with shale interbeds in Miocene age was most susceptible to landslides, whether by the earthquake or by the rain. Most earthquake-induced landslides occurred on the upper part of the slopes and many transported displace material to river channel. The average travel ratio of the earthquake-induced landslide was 1.2.
Study results indicate that the Toraji typhoon-related landslide in 2001 was a secondary disaster of the Chi-chi earthquake. Due to relatively high water content in the displaced material, the average travel ratio of the typhoon-related landslide reached 1.5, greater than the earthquake-induced one.
