Rupture process of the 2015 Mw 7.9 Nepal earthquake and its implications on the seismic risk

Abstract:

The rupture processes of the 2015 April 25 Nepal earthquake and its strongest aftershock occurred on May 12 are investigated by joint inversion of seismological and geodetic data. Our optimized model shows that the rupture has a unilateral propagation pattern. The dominant mechanism is pure thrust with maximum slip of 5.7 m, the rupture scale extends ~60 km along dip and ~150 km along strike, and the associated static stress drop is ~4.2 MPa. The total seismic moment is 7.87×10²⁰ Nm, equivalent to Mw7.9. Most seismic moment was released within 120 s. The strong aftershock magnitude is about Mw7.3, and peak slip is about 5.8 m. Moreover, the slips of the mainshock and the aftershocks are in good complementary, suggesting a triggering relationship between them. This Nepal earthquake ruptured only about 50% of the seismic gap along, thus still poses high earthquake risk, especially in the west of the mainshock.