Mature Diffuse Tectonic Block Boundary Revealed by the 2020 Southwestern Puerto Rico Seismic Sequence
Description:
Distributed faulting typically tends to coalesce into one or a few faults with repeated deformation. The progression of clustered medium-sized (≥Mw4.5) earthquakes during the 2020 seismic sequence in southwestern Puerto Rico (SWPR), modeling shoreline subsidence from InSAR, and sub-seafloor mapping by high-resolution seismic reflection profiles, suggest that the 2020 SWPR seismic sequence was distributed across several short intersecting strike-slip and normal faults beneath the insular shelf and upper slope of Guayanilla submarine canyon. Multibeam bathymetry map of the seafloor shows significant erosion and retreat of the shelf edge in the area of seismic activity as well as slope-parallel lineaments and submarine canyon meanders that typically develop over geological time. The T-axis of the moderate earthquakes further matches the extension direction previously measured on post early Pliocene (~>3 Ma) faults. We conclude that although similar deformation has likely taken place in this area during recent geologic time, it does not appear to have coalesced during this time. The deformation may represent the southernmost part of a diffuse boundary, the Western Puerto Rico Deformation Boundary, which accommodates differential movement between the Puerto Rico and Hispaniola arc blocks. This differential movement is possibly driven by the differential seismic coupling along the Puerto Rico – Hispaniola subduction zone. We propose that the compositional heterogeneity across the island arc retards the process of focusing the deformation into a single fault. Given the evidence presented here, we should not expect a single large event in this area but similar diffuse sequences in the future.
Session: The 2020-2021 Southwest Puerto Rico Seismic Sequence: Current State of Knowledge and Implications
Type: Oral
Date: 4/18/2023
Presentation Time: 09:00 AM (local time)
Presenting Author: Uri S. ten Brink
Student Presenter: No
Invited Presentation:
Authors
Uri ten Brink Presenting Author Corresponding Author utenbrink@usgs.gov U.S. Geological Survey |
Elizabeth Vanacore elizabeth.vanacore@upr.edu University of Puerto Rico, Mayaguez |
Eric Fielding eric.j.fielding@jpl.nasa.gov Jet Propulsion Laboratory, California Institute of Technology |
Jason Chaytor jchaytor@usgs.gov U.S. Geological Survey |
Alberto López-Venegas alberto.lopez3@upr.edu University of Puerto Rico, Mayaguez |
Wayne Baldwin wbaldwin@usgs.gov U.S. Geological Survey, |
David Foster dfoster@usgs.gov U.S. Geological Survey |
Brian Andrews bandrews@usgs.gov U.S. Geological Survey |
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Mature Diffuse Tectonic Block Boundary Revealed by the 2020 Southwestern Puerto Rico Seismic Sequence
Category
The 2020-2021 Southwest Puerto Rico Seismic Sequence: Current State of Knowledge and Implications