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New Airborne Magnetic and Radiometric Survey Over Puerto Rico and Surrounding Offshore Areas

Description: 

Puerto Rico and its surrounding shelf lie within a complex deformation zone associated with oblique subduction of the North American plate under the Caribbean plate. The seismicity rate is high, including both Benioff Zone earthquakes (>30 km depth) and shallow earthquakes (< 10 km depth). Damaging events include the 2020-2021 sequence near the southwestern shore, historical 1867 Mw~7.2 and 1918 Mw~7.1 earthquakes near the northwest shore, and in some cases, associated tsunamis. Because of the tectonic complexity of the region, locations of shallow faults that could be active are poorly known.
Mapping faults in this region poses challenges because many areas of interest are difficult to access. Most onshore areas are densely vegetated, obscuring the surface expression of faults. Offshore areas are covered by shallow (2-20 m) reef platforms limiting ship access for marine geophysical surveys. Aeromagnetic data can assist the identification and mapping of faults both near the surface and at depths where earthquakes occur. However, existing data are limited to a set of surveys flown in 1957 and 1962 that cover less than 40% of the island of Puerto Rico; these pre-GPS, analog data were digitized from contour maps. There are few shipboard magnetic profiles in the shallow shelf areas.
An airborne magnetic and radiometric survey covering the entire island of Puerto Rico and surrounding offshore areas will be flown starting January 2023 as part of a collaborative effort between the USGS Earth Mapping Resources Initiative, Earthquake Hazards Program, and Coastal and Marine Hazards and Resources Program. Data will be collected along north-south flight lines spaced 250 m at heights of ~90-400 m, with greater heights in areas with rugged topography or near population centers. This survey represents the first modern aeromagnetic and first aeroradiometric data to be collected over Puerto Rico. We present preliminary data from this survey and consider potential implications for seismicity in the region.

Session: Active Faults in the Caribbean and Central America [Poster]

Type: Poster

Date: 4/20/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Anjana K. Shah

Student Presenter: No

Invited Presentation: 

Authors