The seismological aftermath of the 2016 Mw7.8 Pedernales, Ecuador earthquake

Stephen Hernandez

Published August 15, 2017, SCEC Contribution #7792, 2017 SCEC Annual Meeting Poster #082

On 16 April 2016, a strong underthrusting earthquake ruptured a ~100 by ~50 km segment of the Nazca-South American margin off the coast of the province of Manabí, Ecuador. Effects of the earthquake included >660 fatalities, a small tsunami, numerous landslides, liquefaction, surficial deformation, and significant structural and infrastructure damage, rendering many city cores as practically uninhabitable. In this article, we present an overview of the major seismological observations recorded in the aftermath of the earthquake. With a hypocenter located near the city of Pedernales, multiple previous studies point to a source with a relatively simple and pulse-like propagation. The earthquake ruptured unilaterally along a predominantly north-to-south axis resulting in a marked directivity effect towards the south. This directivity, coupled with site amplification effects, led to stronger ground motions and heightened damaged observed in municipalities such as Manta, Portoviejo, and Guayaquil. A spatially extensive aftershock sequence was triggered by the coseismic rupture in the months following the earthquake, with three dominant segments being the most active. Preliminary moment tensor solutions of the largest aftershocks primarily show oblique- to reverse-faulting mechanisms along the main plate interface, though some extensional mechanisms have been observed. A b-value analysis over time for seismicity located near the epicenter shows a subtle decrease preceding the earthquake, indicating possible long-term precursory stress loading.

Key Words
megathrust, ecuador

Citation
Hernandez, S. (2017, 08). The seismological aftermath of the 2016 Mw7.8 Pedernales, Ecuador earthquake. Poster Presentation at 2017 SCEC Annual Meeting.

Related Projects & Working Groups
Seismology