M 6.9 September 18, 2011 Sikkim earthquake

Abstract

A strong earthquake (6.9 M_w) occurred in the Sikkim–Nepal region of the Himalayan arc which caused the death of about 100 people. The earthquake involved predominantly strike-slip motion on a steep fault, which is transverse to the Himalaya. It implies that the rupture of this earthquake did not occur on the Himalayan detachment, which slips in a stick-and-slip manner to accommodate 2cm/year of convergence within the Himalaya. Although there is uncertainty about the depth estimates and ambiguity in the fault plane, amongst many other rupture models of the earthquake it is suggested that this, and a similar such earthquake on 20 August 1988 in the Himalayan foothills, occurred in response to the subduction of the Munger-Saharsa ridge on the Indian plate. The occurrence of this earthquake highlights the role of transverse features in the Himalayan tectonics.