The Impact of the Great 1950 Assam Earthquake on the Frontal Regions of the Northeast Himalaya

Abstract

The Himalaya, world’s highest mountain range, harbours some of the world’s greatest intra-continental earthquakes. The Northeast Himalayan mountain belt experienced two great earthquakes of 1897 - Shillong (M = 8.7) and 1950 - Assam (M = 8.6). The great 1950 Assam earthquake caused widespread devastation throughout the frontal regions of Northeast Himalaya. Though this earthquake is known as the Assam Earthquake, its epicenter was located in the territory adjacent to the Mishmi Hills of Arunachal Pradesh of India, in higher reaches of the Lohit river near Rima, Tibet. It was the tenth largest earthquake of the twentieth century (USGS 2011). This earthquake was caused by the convergence of two continental plates of India and Eurasia and it was felt throughout the Eastern India. The ground cracked and fissured, bridges, rail lines were destroyed and river beds silted up. Immediately after the shock, several tributaries of Brahmaputra River were blocked by landslips caused by the violent shaking of the earthquake causing drastic flooding afterwards. This great earthquake, destructive in Assam, Arunachal Pradesh and Tibet (China), was an important earthquake event since the introduction of seismological observing stations. Alterations of relief were brought about by many rock falls in the Mishmi Hills and destruction of forest areas. Till now, there are no surface rupture zone findings for the great 1950 Assam Earthquake, even though it was suggested to have occurred along the Po-Chu Fault in Tibet, China. This earthquake changed topographical features in the Eastern Syntaxis and caused havoc in the frontal region of Northeast Himalaya, making drastic impact on human civilization.