Topographic locations and size of earthquake- and typhoon-generated landslides, Tachia River, Taiwan

Abstract

Analysis of mapped landslide locations using a high-resolution (5-m grid) digital elevation model (DEM) in the Tachia River basin, Taiwan, finds distinct differences in the topographic locations and size of landslides during the 1999 Chi-Chi earthquake and the 2001 Toraji typhoon. Our analysis supports Densmore and Hovius' hypothesis that earthquake-induced landslides cluster near ridgetops due to topographic amplification of ground shaking, and that typhoon-induced landslides occur with greater frequency lower on slopes. In addition, the differing topographic locations of seismically-induced and subsequent typhoon-induced landslides shows no evidence of residual post-earthquake influences on landslides during typhoon Toraji previously hypothesized for drainage basins closer to the earthquake epicenter. Our results support the interpretation that in this tectonically active landscape, seismically-induced landslides help shatter and erode ridgetops but typhoon-triggered landslides concentrate erosion farther downslope, with the combination acting to more uniformly lower upland terrain than either process does individually. © 2013 John Wiley & Sons, Ltd.