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Searching for Holocene Slip on the Cerro Goden Fault, Western Puerto Rico

Description: 

Identification of Holocene-active onshore faults in Puerto Rico (PR) is key to seismic preparedness on the island and to appraisal of long-term seismic hazard. Human development, vegetation, relatively low sedimentation and high denudation rates, and destructive storms can obscure paleoseismic targets. Here, we develop a crustal stress map of PR that is used to winnow candidate traces identified from aerial and satellite imagery for paleoseismic investigations. The Cerro Goden fault zone (CGFZ) is mapped onshore and offshore in western Puerto Rico. Marine seismic and bathymetric data provide evidence for Holocene rupture and sediment deformation along several 1–3 km long, subparallel strands trending N75E to N88E. Onshore, the CGFZ appears to continue N80E for 4 km along the southern boundary of the La Cadena de San Francisco mountains before rotating to N100E, then to N110E, and splaying into the Great Southern Puerto Rico fault zone. Until recently, however, crustal stress field constraints in Puerto Rico were limited to a single near-shore and five offshore moment tensors with normal mechanisms. With 250 moment tensors now available, albeit none directly along the CGFZ, we create a crustal stress map of the island. Oblique motion dominates with secondary extension rotating from N140E in the northwest to N150E near the Indios sequence. Fault slip potential modeling in the vicinity of the CGFZ shows that steep, ~N20E or N80E strike-slip faults and ~N50E normal faults are optimally oriented for slip, but faults striking between N95E and N185E are unlikely to undergo frictional failure. With these considerations in mind, several potential new trenching sites are identified west near the coastline where the CGF trends N80E.

Session: Active Faults in the Caribbean and Central America

Type: Oral

Date: 4/20/2023

Presentation Time: 10:30 AM (local time)

Presenting Author: Jamey Turner

Student Presenter: No

Invited Presentation: 

Authors