Evidence for a Great Medieval Earthquake (~1100 A.D.) in the Central Himalayas, Nepal

Abstract

The Himalayan orogen has produced three thrust earthquakes with moment magnitude ( M _w ) 7.8 to 8.5 during the past century, yet no surface ruptures associated with these great earthquakes have been documented. Here, we present paleoseismic evidence from east central Nepal that, since ∼700 A.D., a single earthquake ruptured the Frontal Thrust fault at ∼1100 A.D., with a surface displacement of ∼17 (+5/–3) meters and a lateral extent and size that could have exceeded 240 kilometers and ∼ M _w 8.8, respectively. Ruptures associated with M _w <8.2 events would contribute to the frontal Himalayas folding but would stop before reaching the surface. These findings could require substantial modifications to current regional seismic hazard models.