Seismic Velocity Structure and Geologic Controls on Seismicity Surrounding the April 1, 2014 Pisagua, Chile Earthquake

Date: 4/25/2019

Time: 06:00 PM

Room: Grand Ballroom

Correlations between crustal structure, residual gravity anomalies, and seismicity associated with the 2014 Mw 8.2 Pisagua/Iquique earthquake indicate that geologic structure plays a role in controlling subduction-related seismicity off the coast of northern Chile. The 2014 sequence of events ruptured ~200 km of a ~500 km section of the subduction zone where no significant seismicity had occurred since the late 1800s. The remaining unruptured section corresponds to a region of high residual gravity and poses a significant risk for future large earthquakes. To investigate the relationship between the observed seismic behavior and geologic characteristics, the PICTURES project used the R/V Marcus G. Langseth to acquire a 3D controlled-source seismic data set in 2016. The internationally collaborative project included contributions from Oregon State Univ., GEOMAR, the Univ. de Chile, and the Univ. of Liverpool to record ~45000 airgun sources on 70 OBS, 50 land-based stations, and a grid of ~5000 km of seismic reflection data. Seismic P-wave velocity models based on the OBS data reveal along-strike variations in the crustal structure of the forearc that correspond to the slip distribution of the Pisagua earthquake sequence and the high gravity anomaly. The 3D grid of data allows high-resolution seismic imaging of the velocity and reflectivity structure in the region that ruptured in 2014, and the high-resolution ship-board gravity data constrains the gravity anomaly associated with the southern end of rupture propagation. The relationship between geologic structure and seismic activity has implications for seismic behavior in other subduction zones with significant along-strike geologic heterogeneity. The MGL1610 Science Party includes Anne Tréhu, Emilio Vera, Michael Riedel, Kathy Davenport, Florian Petersen, Emma Myers, Carsten Lehman, Felipe Gonzalez Rojas, Sara Alhisni, Jan Handel. Additional collaborators include Andreas Rietbrock, Eduardo Contreras-Reyes, Heidrun Kopp, Diana Comte, Jacob Geersen, Bo Ma, Cristian Rodrigo, and Juan Diaz.

Presenting Author: Kathy Davenport

Authors