Earthquakes in India: Hazards, genesis and mitigation measures

Abstract

Earthquake, as its name suggests, means shaking of the ground which is caused by a sudden release of stored elastic energy in the rock mass that had accumulated as strain over time along faults. Seismic waves are generated due to sudden release of energy which extend outward from the point of origin (called epicenter) like water ripples. The speed of these waves depends on the geologic composition of the materials through which they pass. Earthquakes can occur at a range of depths, and the focal depths (distance below the earth's surface at which accumulated energy is released) from 0 to 70 km are considered shallow, from 70 to 300 km are considered intermediate and greater than 300 km are considered deep (Richter, 1958). Some 50,000 earthquakes occur on an average every year as the earth's tectonic plates shift and adjust, including some of potentially devastating magnitude releasing enormous amounts of energy. Approximately 75% of the world's population live in the areas that were affected at least once by natural disasters namely earthquake, tropical cyclone, flood or drought between 1980 and 2000 (UNDP, 2004). Potential earthquakes often cause considerable causalities and economic damage, coupled with significant hydrologic/hydrogeologic changes (e.g., UNDP, 2004; Allen, 2007; Manga and Wang, 2007). In addition, many secondary hazards/disasters such as landslides, rockfalls, avalanches, tsunamis, etc. are known to occur in the aftermath of an earthquake. © 2010 Springer Science+Business Media B.V.