EARTHQUAKE-INDUCED LANDSLIDES FROM 1789 BC TO 2005 AD

Earthquake-induced landslides have been described from as long ago as 1789 BC, but most accounts from before the late eighteenth century AD are incomplete and vague. Modern studies began with a report on the 1783 Calabria, Italy earthquake, and the development of knowledge about earthquake-induced landslides since then can be divided into several periods. Between 1783 and the first use of aerial photography in 1948, landslides were documented by ground-based studies often carried out by formal scientific commissions. These studies typically identified and described some but not all of the landslides triggered by an earthquake. Aerial photography made it feasible to prepare accurate and comprehensive maps of the landslides triggered by an earthquake, and since 1948 several such post-earthquake inventories have been prepared. Since 1989, digital mapping and GIS techniques have come into use, greatly enhancing the level of analysis that can be applied to earthquake-induced landslide occurrence. To define the general characteristics of landslides triggered by earthquakes, the first broad-scale synthesis of existing data was completed in 1984. This study classified the types of landslides triggered by earthquakes, related landslide numbers and distribution to geologic and seismic parameters, and identified the hazards associated with these landslides. Since then, additional studies of worldwide data (1999) and regional data from New Zealand (1997), Greece (2000), Italy (2000), and Central America (2002) have refined and extended this general knowledge. However, despite more than two centuries of modern studies, the number of earthquakes with relatively complete data on landslide occurrence is still small. One of the most pressing research needs in the field of seismogenic landslide studies is for complete post-earthquake inventories of many more events in a wide variety of geologic and seismic environments.