A New Fault Characterization in Lajas Valley, Southwestern Puerto Rico
Description:
Southwestern Puerto Rico (SWPR) received significant attention after the 2020-ongoing earthquake sequence, which included events located near offshore Guayanilla Canyon. Previous research suggested that this seismicity migrated onshore along left-lateral strike slip and transtensional faults, including the Punta Montalva and South Lajas faults, respectively. Most of previous geophysical work in this region was conducted through offshore seismic reflection surveys, leaving significant gaps for understanding the subsurface character of onshore faults. Strikes, dips, and depths of potentially active fault planes are critical factors to comprehensively characterize faults in tectonically active regions and for updating future seismic hazard assessments. Seismic reflection profiles were collected in the Spring of 2023 and 2024 across Lajas Valley, SWPR, to produce a new onshore fault characterization of the South Lajas Fault and other associated faults. Two phases of data acquisition were completed using a 216-channel seismic system with a weight-drop source. Profiles were collected perpendicular to the strike of the valley, and spanned the entire valley. Seismic data processing and data analyses were carried out using the Seismic Unix processing system. Ground Penetrating Radar (GPR) surveys were completed in Fall 2024 along the same profile location to characterize structures and potential faulting in the upper 20 m of the valley’s subsurface using the open-source R language processing software RGPR. Preliminary seismic results showed excellent imaging of southward-thickening stratigraphy that record faulting associated with the South Lajas Fault up to 250 m depth along with interpretation of depositional events before, during, and after tectonic activity in Lajas Valley. GPR data displayed near-surface layers and two discontinuous features possibly related to faulting to at least 10 m depth. This information will help illuminate the structure and tectonic evolution of Lajas Valley along the SWPR boundary.
Session: Earthquakes, Lithospheric Structure, and Dynamics in Stable Continental Region [Poster]
Type: Poster
Date: 4/17/2025
Presentation Time: 08:00 AM (local time)
Presenting Author: Chris
Student Presenter: Yes
Invited Presentation:
Poster Number: 63
Authors
Chris Justiniano Presenting Author Corresponding Author chris.justiniano@upr.edu University of Puerto Rico, Mayagüez |
Elizabeth Vanacore elizabeth.vanacore@upr.edu University of Puerto Rico, Mayagüez |
Thomas Pratt tpratt@usgs.gov U.S. Geological Survey |
Alberto López Venegas alberto.lopez3@upr.edu University of Puerto Rico, Mayagüez |
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A New Fault Characterization in Lajas Valley, Southwestern Puerto Rico
Category
Earthquakes, Lithospheric Structure, and Dynamics in Stable Continental Regions