Landslides in Eastern Honshu Induced by the 2011 Off the Pacific Coast of Tohoku Earthquake

In this article we discuss the character and spatial pattern of coseismic landslides from the eastern Honshu region of Japan, which was strongly shaken in the 2011 Tohoku earthquake. We developed a detailed geospatial database of 3477 landslides based on postearthquake field surveys and examination of high-resolution satellite imagery across a 28; 380 km(2) landslide study area. Analysis of the database shows that a substantial majority (80%) of landslides occurred in Quaternary soil and Neogene rock units. Despite their abundance in the study area, relatively few landslides occurred in pre-Neogene rocks (i.e., older than 23 Ma). Further examination of the data showed that the most common types of landslides were (1) disrupted landslides in Neogene sedimentary rocks and (2) lateral spreading in Quaternary sediments. However, we found that coseismic landslide erosion (i.e., debris mobilization) was almost fully dominated by lateral spreading within Quaternary sediments. When comparing the landslide inventory with ground motions recorded by dense regional seismic arrays, we found no statistically significant correlation between landslide intensity and ground motion within the study area.