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Unveiling Seismic Hazards: Paleoseismic Insights From the La Venta Fault in the Forearc Mountains, Mexico

Description: 

Understanding the potential earthquake activity of unknown active faults is crucial for assessing seismic hazards in continental interiors. Despite advancements, our knowledge of earthquakes on crustal faults away from plate boundaries, particularly in forearcs, remains incomplete. This study addresses this gap by utilizing paleoseismic records, conducting a LIDAR flight to develop a DTM in the highly vegetated mountains, mapping geomorphological features, performing a geophysical survey including electric resistivity and georadar, and excavating a paleoseismic trench along the central section of the La Venta Fault, named Agua del Perro. The trench revealed six rupturing events over the last 8000 years.

The surface expression of this fault is subtle, characterized by a gentle scarp, minor stream offsets, and a shutter ridge. Our data show evidence of surface fault rupturing with lateral displacement up to ~80 cm per event and vertical displacement up to 44 cm. The most recent event occurred around the 14th century, registering a calculated magnitude of Mw 6.9. Given the fault's location, our findings suggest a significant seismic risk to local communities along the fault and populations in larger cities like Chilpancingo, Acapulco, and Mexico City. The study also highlights potential damage to infrastructure, such as the La Venta Dam, and associated hazards, including flooding and rock falls. This research emphasizes the importance of recognizing the potential hazard posed by crustal intraplate faults away from plate boundaries in the forearc mountains.

Session: From Faults to Fjords: Earthquake Evidence in Terrestrial and Subaqueous Environments - IV

Type: Oral

Date: 5/1/2024

Presentation Time: 05:30 PM (local time)

Presenting Author: Luis

Student Presenter: No

Invited Presentation: 

Authors