UTIG RESEARCH PROJECTS ARCHIVE

Principal Investigator: Paul Mann
Funded by: U.S. Geological Survey

The islands of Puerto Rico and Hispaniola are within the seismically active North America-Caribbean plate boundary zone. Marine geophysical surveys of the offshore area north of Puerto Rico and on- and offshore mapping in the Dominican Republic have shown this plate boundary to be a mainly submarine, left-lateral strike-slip fault system that extends over 3200 km from the Lesser Antilles arc in the east to the Middle America trench in the west. A large earthquake on this fault in the Puerto Rico-Hispaniola segment of the plate boundary fault could severely affect this densely populated and rapidly developing area.

This project funded by the USGS National Earthquake Hazards Reduction program aims to better understand the longterm, geologic record of earthquakes and strain accumulation along this potentially hazardous plate boundary fault zone. In order to establish this record, five trenches have been excavated across the critical subaerial segment of the plate boundary fault in the Cibao Valley of the Dominican Republic. These excavations combined with radiocarbon dating of soil horizons in the trench have revealed the occurrence of three, large prehistoric (pre-1492) earthquakes that ruptured this segment of the fault zone. Researchers also measured the amount of vertical and offset associated with the most recent of these events about 700 years ago using 3-D excavation techniques. In addition to the trench study, a measurement of the amount of offset on terrace risers offset by many strike-slip rupture events on the fault. These values and radiocarbon dating of the terrace material provide good control on the longterm slip rate between the two plates. Current work is being done to integrate these geologic observations of fault behavior with GPS-based geodetic studies of motion over the past 10 years in the Puerto Rico-Hispaniola segment of the plate boundary.

Publications based on or related to this study:
Prentice, C. S., Mann, P., Taylor, F. W., Burr, G., and Valastro, S., 1993, Paleoseismicity of the North American-Caribbean plate boundary (Septentrional fault), Dominican Republic: Geology, v. 21, p. 49-52.

Mann, P., Prentice, C., Burr, G., Peña, L., and Taylor, F. W., 1998, Tectonic geomorphology and paleoseismology of the Septentrional fault zone, Dominican Republic, in J. F. Dolan and P. Mann, editors, Active Strike-slip and Collisional Tectonics of the Northern Caribbean Plate Boundary Zone, Geological Society of America Special Paper 324, p. 63-123.

Bilich, A., Frohlich, C., and Mann, P., 2001, Global seismicity characteristics of subduction-to-strike-slip transitions: Journal of Geophysical Research, v. 106, p. 19,443-19,452.

Calais, E., Mazabraund, Y, Mercier de Lepinay, B., Mann, P., Mattioli, G., and Jansma, P., 2002, Strain partitioning and fault slip rates in the northeastern Caribbean from GPS measurements: Geophysicsal Research Letters, v. 29, no. 18, 1856, doi:10:1029/2002GL015397, 2002.

Mann, P., Calais, E.,Ruegg, J-C., DeMets, C., Jansma, P., and Mattioli, G., 2002, Oblique collision in the northeastern Caribbean from GPS measurements and geological observations: Tectonics, v. 21, no. 6, 1057, doi:10.1029/2001TC001304, 2002.

Prentice, C., Mann, P., Pena, L., and Burr, G., 2002, Slip rate and earthquake recurrence along the central Septentrional fault, North American-Caribbean plate boundary, Dominican Republic, Journal of Geophysical Research, in press.