Probable role of sediments in blinding the rupture - lessons from the 2004 Sumatra-Andaman earthquake and implication for the Himalayan earthquakes

Abstract

Several evidences show that during the 2004 Sumatra–Andaman earthquake, the rupture in the Andaman region did not extend up to the trench. Consistent with the earthquake processes at several subduction zones of the world, we propose that subducted unconsolidated sediments of Ganga and Brahmaputra rivers on the Indian plate make the shallow portion of the plate boundary interface behave aseismically and hence the rupture remained blind in the Andaman region. We propose that a similar situation exists in the Himalayan region where the subducted sediments of the Indo-Ganga plains under the Outer Himalaya limit the up-dip rupture propagation during great and major earthquakes. In such a case, rupture during great and major earthquakes may not extend up to the surface. Lack of evidence of surface faulting during the past major and great Himalayan earthquakes is consistent with this idea.