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Evidence for Geologic Influence on Subduction Zone Seismicity during the 2014 Mw 8.2 Pisagua/Iquique, Chile Earthquake Sequence from Amphibious Controlled-Source Seismic Data

Session: Amphibious Seismic Studies of Plate Boundary Structure and Processes

Type: Oral

Date: 4/20/2021

Presentation Time: 10:30 AM Pacific

Description: 

The 2014 Mw 8.2 Iquique earthquake offshore northern Chile partially ruptured a seismic gap that had not experienced a great earthquake since 1877. The spatial distribution of fore- and aftershocks associated with the 2014 event is correlated to residual gravity anomalies and variations in forearc structure, indicating that crustal structure affected the distribution of subduction-zone related seismic deformation. To provide insight into the relationship between geologic characteristics of the upper and lower plates and observed seismic behavior in the source region we acquired 3D controlled-source seismic data across the forearc in northern Chile. The coordinated marine and onshore efforts of the 2016 PICTURES (Pisagua/Iquique Crustal Tomography to Understand the Region of the Earthquake Source) project included deployment of 70 ocean-bottom and 50 onshore stations to record ~4400 km of seismic reflection/refraction lines using the tuned airgun array on the R/V Langseth. The wide-aperture amphibious data provide 3D ray coverage across the forearc from the trench into the Coastal Cordillera from ~19°S-20.5°S. Data include arrivals parallel and perpendicular to the trench, including crustal Pg arrivals and reflections from the Moho of the subducting plate. Using traveltime tomography, we image high-resolution 3D P-wave seismic velocity structure in the region of the 2014 earthquake sequence. Results illuminate along-strike heterogeneity in upper plate seismic velocity structure, and correlations between seismic structure, residual gravity anomalies, and the 2014 earthquake sequence highlight the importance of geologic structure in controlling plate boundary evolution and the potential for megathrust seismic activity.

The PICTURES science team includes: Andreas Rietbrock, Felipe Gonzales Rojas, Bo Ma, Emma Myers, Florian Petersen, Eduardo Contreras-Reyes, Emilio Vera, Heidrun Kopp, Dietrich Lange, Michael Riedel, Dirk Klaeschen. Work presented in this abstract was performed at Oregon State University. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.

Presenting Author: Kathy Davenport

Student Presenter: No

Authors