A statistical model for the impact of the 1999 Chi-Chi earthquake on the subsequent rainfall-induced landslides

A statistical model is proposed for the temporal impact of the 1999 Chi-Chi earthquake on the subsequent rainfall-induced new landslides in the Choushui River Watershed of Central Taiwan. Based on daily precipitation records from 1996 to 2008 and the landslide inventories obtained from satellite images taken in this period, the parameters of the model functions were obtained by genetic algorithm. The proposed model estimates new-landslide density from daily precipitation with an average error of 13.91% to the variation analysis result from landslide inventory over 15 image dates. The model estimation reveals a continuously decaying pattern of earthquake impact on the subsequent rainfall-induced new landslides, an average daily 0.004‰ background new-landslide density, and a 4.97‰ new-landslide density caused by the earthquake directly within the study area. Also, the model suggests that there are impacts and latency of antecedent precipitation among the occurrence of new landslides.