Hazard and risk related to earthquake-triggered landslide events

Abstract

First, we analyse how important earthquake-induced landslide hazards are compared to other geohazards at world-wide scale. Then, we try to estimate where these hazards may have the strongest impacts—at regional and local scale. In this regard, we also consider the short- and long-term effects of geological, tectonic, climatic and morphological conditions. Hazard and risk related to these processes was also analysed based on series of case histories: E.g., the 1920 Haiyuan earthquake-landslide disaster in China, the 1970 Nevado-Huascaran rock avalanche, as well as the 1999 events in Taiwan, 2001 in El Salvador, 2005 in Pakistan, and 2008 in China. Detailed report was provided for events in Central Asia: the 1911 earthquakes in Kemin, Sarez in 1911, Khait in 1949, Gissar in 1989 and Suusamyr in 1992. Particular focus is on mega-events such as the Usoy rockslide in Tajikistan as well as giant prehistoric rockslides in other parts of Central Asia and in the world (including Europe). We will try to answer several questions such as: how likely is a seismic versus climatic origin for giant landslides; how is the general geohazards level affected by these low-frequency earthquake-triggered mega-events. One conclusion is that in semi-arid mountain regions marked by a strong seismic activity, such as those in Central Asia, seismogenic landslides and related long-term effects may represent the most important geohazards. Further, the susceptibility to seismic slope instability is highest along active fault zones and on convex slopes made of soft or fractured materials.