Coseismic Ground Rupture of the 15 October 2013 Magnitude (MW) 7.2 Bohol Earthquake, Bohol Island, Central Philippines

Abstract

The 15 October 2013 magnitude (MW) 7.2 Bohol earthquake produced an ~50-km-long, ~12-km-wide northeast trending zone of uplift with an ~8-km-long discontinuous ground rupture indicating predominantly reverse-slip movement on a southeast dipping fault. Documentation of the nearly continuous northern terminus of the 2013 Bohol earthquake ground rupture revealed its association to preexisting scarps of the previously unmapped, Quaternary-active North Bohol Fault. Trenching across the rupture at four sites not only reveals the geometry and kinematics of the fault but also shows at least one or two pre-2013 surface rupturing events. Onshore geologic mapping and offshore seismic reflection profiles demonstrate the presence of an island-wide, northeast-southwest trending fold-and-thrust belt through which deformation related to the regional shortening across the Visayan Sea Basin in the central Philippines is likely distributed.