UC Santa Cruz

On 1 April 2014, a great (Mw8.1) interplate thrust earthquake ruptured in the northern portion of the 1877 earthquake seismic gap in northern Chile. The sequence commenced on 16 March 2014 with a magnitude 6.7 thrust event, followed by thrust-faulting aftershocks that migrated northward ~40km over 2weeks to near the main shock hypocenter. Guided by short-period teleseismic P wave backprojections and inversion of deepwater tsunami wave recordings, a finite-fault inversion of teleseismic P and SH waves using a geometry consistent with long-period seismic waves resolves a spatially compact large-slip (~2-6.7m) zone located ~30km downdip and ~30km along-strike south of the hypocenter, downdip of the foreshock sequence. The main shock seismic moment is 1.7×1021N m with a fault dip of 18°, radiated seismic energy of 4.5-8.4×1016J, and static stress drop of ~2.5MPa. Most of the 1877 gap remains unbroken and hazardous. © 2014. American Geophysical Union. All Rights Reserved.