The Mw 7.3 Papanoa, Mexico earthquake of April 18, 2014: Implications for recurrent M > 7 thrust earthquakes in western Guerrero

Abstract

We apply a single-step, finite-fault waveform inversion procedure to derive a coseismic slip model for the large MW 7.3 Papanoa, Mexico earthquake of 18 April 2014 using broadband teleseismic body waves. Inversion of the P and SH ground-displacement waveforms yields a rupture model characterized by two principal sources of slip in the northwest portion of the Guerrero coast. The region is also the site of several M > 7 earthquakes in 1943, 1979 and 1985. A comparison of the 2014 slip model with ruptures observed for the 1979 and 1985 earthquakes suggests that the zones of high slip do not spatially coincide, despite similarities in the size and location of their aftershock areas. The zones of high coseismic slip are interpreted to represent asperity areas along the Cocos- North America plate boundary, and their limited spatial overlap from one event to another indicates that the rupture characteristics of recurring M > 7 thrust earthquakes in this portion of western Guerrero have not repeated in the last 70 years. The abutting nature of the asperities suggests that future large M > 7 earthquakes are likely to involve interplate patches between areas where large coseismic failure has been recently observed. Also, the observed asperities and their intervening regions may define locations where seismic failure may occur in future megathrust events. The results have important implications for the potential and recurrence of large M > 7 subduction earthquakes and the estimation of the strong ground motions expected from these events.