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Book Chapter

Historical earthquakes of the Puerto Rico–Virgin Islands region (1915–1963)

By
Diane I. Doser
Diane I. Doser
Department of Geological Sciences, University of Texas at El Paso, El Paso, Texas 79968-0555, USADoser: doser@geo.utep.edu. Present addresses: Rodriguez—Exxon-Mobil Corp., Houston, Texas, USA; Flores—University of California at Santa Cruz.
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Christina M. Rodriguez
Christina M. Rodriguez
Department of Geological Sciences, University of Texas at El Paso, El Paso, Texas 79968-0555, USA
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Claudia Flores
Claudia Flores
Department of Geological Sciences, University of Texas at El Paso, El Paso, Texas 79968-0555, USA
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Published:
January 01, 2005

We have collected and modeled the seismograms of historic earthquakes of M >6.0 occurring in the Puerto Rico and Virgin Islands region between 1915 and 1963. Study of offshore events in the north Mona Passage region indicate likely rupture along the North America plate interface in 1915 (MW = 6.7), 1920 (MW = 6.5), and 1943 (MW = 7.8 and 6.0) at depths of 20–30 km. (MW is moment magnitude.) An event in 1917 (MW = 6.9) involved strike-slip faulting possibly within the subducting North America plate (36 ± 7 km). The 1918 central Mona Passage earthquake (MW = 7.2) represents normal-oblique faulting at ∼20 km depth. This earthquake generated a tsunami that killed over 100 people on the island of Puerto Rico. The event has a complex source-time function, suggesting rupture along several fault segments. This is consistent with previous tsunami modeling studies. An event in 1916 in southeastern Hispaniola (MW = 6.8) occurred at a depth of ∼16 km, with a reverse faulting mechanism similar to aftershocks of the 1946 great Hispaniola earthquake. Within the Virgin Islands region, we studied three moderate (M ∼6–6.5) events. An event in 1930 (MW = 6.0) appears to involve strike-slip faulting, possibly within the subducting North America plate, while events in 1919 and 1927 (MW = 6.2 and 5.6) are consistent with rupture along the plate interface. An event in 1939 (MW = 6.4), located well to the north of the Puerto Rico trench, appears to be a normal faulting event in the outer rise. Slip vectors for earthquakes along the plate interface show northeastward directed slip (∼50°) of the Greater Antilles crust relative to the North America plate in the Virgin Island region, north-northeast (∼27°) directed slip in the northeast Mona Passage (east of 67.5°W), and east-northeast (∼70°) directed slip in the northwest Mona Passage. Normal faulting events in the Greater Antilles crust suggest southeast-northwest oriented extension. Over the past ∼85 yr, 87% of the seismic moment release has occurred on structures to the north and northwest of Puerto Rico. This is comparable to estimates of the amount of plate motion that is occurring across these structures from global positioning system and geodesy studies.

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Contents

GSA Special Papers

Active Tectonics and Seismic Hazards of Puerto Rico, the Virgin Islands, and Offshore Areas

Paul Mann
Paul Mann
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Geological Society of America
Volume
385
ISBN print:
9780813723853
Publication date:
January 01, 2005

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