Slip history of the 2016 Mw 7.0 Kumamoto earthquake: Intraplate rupture in complex tectonic environment

Abstract

Rupture history of the 2016 Mw 7.0 Kumamoto earthquake is constrained by using the waveforms of strong motion observations, teleseismic broadband body waves, and long-period surface waves. Its fault geometry is modeled with Hinagu (orienting 205° and dipping 73°) and Futagawa (orienting 235° and dipping 60°), two segments. The result reconciles the difference between moment tensor solutions and the surface fault trace. It reveals a complex rupture process that initiated on the Hinagu segment in dextral motion, propagated northeastward unilaterally, and after 15 s ceased near Aso volcano with normal fault motion. The average slip, rise time, and slip rate are 1.8 m, 2.0 s, and 1.2 m/s, respectively. The rupture broke through an ~30° fault intersection without notable delay, which can be a result of dynamic “unclamping.” The northeast boundary of the largest asperity might mark the bottom of the seismogenic zone, which becomes shallower gradually near Aso volcano.