Morphology, structure, and tectonic evolution of the Mona Canyon, Puerto Rico

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
Steven A. Mondziel (Creator)
The University of North Carolina Wilmington (UNCW )
Web Site:
Nancy Grindlay

Abstract: The Mona Canyon is a z-shaped, 20-30 km-wide, 140 km-long, and 2-3.5 km-deep atypical submarine canyon that incises the Greater Antilles island arc off the northwest coast of Puerto Rico. This is the first study to systematically integrate multiple sets of marine geophysical data, including multibeam bathymetry, sidescan sonar imagery, single- and multi-channel seismic reflection profiles, and earthquakes to evaluate the morphology, structure, and the tectonic evolution of the Mona Canyon. The data suggest that the Mona Canyon is a half-graben structure that is controlled by the listric Mona Canyon master fault on the east side of the canyon, and antithetic faults on the west side of the canyon. The interpreted marine geophysical data leads to a proposed extensional model for the formation of the Mona Canyon. A structural restoration of the central Mona Canyon performed in this study indicates that extension in the Mona Canyon appears to have initiated in the Middle Oligocene, approximately 30 Ma. This is in contrast to the previous estimate of 1.2 Ma that was predicted using differential GPS vectors between Hispaniola and Puerto Rico. The extension is proposed to have occurred over two phases. Phase I occurred from the Middle Oligocene to Late Miocene, and was a slow, initial stage of at least 1.66 km. Phase II occurred from the Late Miocene to the Recent, and was a more rapid, late stage extension of at least 4.39 km, for a total minimum extension through the Recent of 6.05 km. On October 11, 1918, a M7.2 earthquake near the southern end of the Mona Canyon generated a 4-6 m-high tsunami that inundated the northwest coast of Puerto Rico, and claimed over 100 lives. This study presents evidence for a 7 km-wide, 200 m-high amphitheater-shaped headscarp in the southern Mona Canyon that is located in the same region as two submarine cable breaks that occurred after the 1918 tsunami. Numerical modeling performed using the southern Mona Canyon mass wasting feature as a source mechanism for the deadly 1918 tsunami generates a wave that matches well with the observed 4-6 m-high run-up, phase, and timing.

Additional Information

A Thesis Submitted to the University of North Carolina at Wilmington in Partial Fulfillment of the Requirement for the Degree of Masters of Science
Language: English
Date: 2009
Geology--Puerto Rico--Mona Canyon
Geology -- Puerto Rico -- Mona Canyon

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