Effect of Earthquake on Subsequent Typhoon-Induced Landslides Using Remote Sensing Imagery in the 99 Peaks Region, Central Taiwan

Abstract

The effect of Chi-Chi earthquake on typhoon-triggered landslides was estimated using accuracy curves method in seismic landslide hazard model. The logistic regression model and geographic information system (GIS) are chosen to perform the seismic landslide hazard analysis. An inventory map of the landslides from SPOT images taken before and after the events was used to produce a dependent variable, which takes a value of 0 and 1 for the absence and presence of landslides. A set of independent parameters include lithology, elevation, slope gradient, slope aspect, terrain roughness, land use and Arias intensity (Ia) with topographic effect. Subsequently, the logistic regression is used to find the best fitting function to describe the relationship between occurrence or non-occurrence of landslides within an individual grid cell. The decreased effect of the earthquake was measured using accuracy curves method. It found that the effect of earthquake decreases with time. The landslide events of 2004 had little correlation with the Chi-Chi earthquake. Nevertheless, after period of 5 years, the seismic intensity from the Chi-Chi earthquake might still have affected conditions of landslides in the study area.