Abstract
The 2004 Mid-Niigata Prefecture earthquake induced many landslides in the Higashiyama Hills, central Japan. The epicenter of the earthquake was near the axis of an active fold called the Higashiyama anticlinorium, but the density of earthquake-triggered landslides was relatively low around the anticlinorium's axis. In contrast, landslide density was high on both limbs of the anticlinorium. This study analyzes the factors responsible for this difference in earthquake-induced landslide density from the viewpoints of landform development and microgeomorphology. The folding of the Higashiyama anticlinorium since the latest early Pleistocene has been uplifting the Higashiyama Hills; the 2004 earthquake was one event of this crustal movement. Microgeomorphological classification using a 2-m-mesh DEM around the middle fork of the Imo River indicates that landslide density is high on the steep slopes of the river valley, which are dissected by down-cutting of the Imo River and its tributaries. In contrast, the area around the axis of the Higashiyama anticlinorium is characterized by deep-seated landslide geomorphology, without dissecting valleys, and relatively low relief. As a result, earthquake-induced landslides are sparse there. These differences in slope geomorphology reflect geomorphic processes in actively uplifting hills and mountains with active folding. This viewpoint is applicable to estimating the potential for co-seismic landsliding.
