Secondary Hazards Associated with Coseismic Landslide

Landslide hazards induced by earthquakes are classified into a primary hazard and a secondary hazard from temporal and spatial viewpoints of damages. Working Group 3 (WG-3) of the Earthquake-induced Landslides Research Projects comprehensively investigated the secondary hazards associated with coseismic landslide. First of all, we provided a definition of them as the landslide hazard occurred with a delay in time and over a wider area, which triggered by post-seismic rainfall, snowmelt and transportation of debris. Then we collected past cases of the secondary landslide disasters, classified them by time scale and disaster type. This paper reports on some major secondary landslide disasters according to our classification as follows: (1) Formation and break of landslide dams, (2) Post-seismic landslides, (3) Long-term degradation of mountainous forest watershed, (4) Isolated districts due to traffic disruption and functional decline of countermeasure works.