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From AGU's website.The UNIVERSITY of TEXAS at AUSTIN
INSTITUTE FOR GEOPHYSICS
NewsHR: 0830h
AB: The Mona Passage, west of Puerto Rico, forms the western boundary of the Puerto Rico - Virgin Islands microplate (PRVI). This region is seismically active, averaging one event per day, and there are 40 documented historical events in the last 500 years. A high-resolution seismic and sidescan sonar survey of the insular shelf of western and southern Puerto Rico was conducted during May, 2000, in an effort to identify Late Holocene fault activity and to further assess seismic hazards in the region (see Grindlay et al., this session). We focus on a portion of the surveyed area offshore western Puerto Rico extending from Punta Higuero through Bahia de Mayag\"{u}ez. This area was targeted as a likely location to image recent faults because of evidence of faults identified by multichannel seismic data collected by Western Geophysical in 1972 and the presence of a relatively thick covering of recent deltaic sediments deposited by the Rio de A\~{n}asco. Observations of linear offsets in seafloor features and a unsedimented submarine ridge immediately south of the mountains of La Cadena de San Francisco are consistent with recent activity along the Cerro Goden fault zone (also see Lao et al., this session). The submarine ridge parallels the coastline as it curves from a W to NW trend at Punta Cadena, possibly extending to the Desecheo Ridge, the southern limit of the Mona Rift Zone. Within Bahia de Mayag\"{u}ez and Bahia de A\~{n}asco folding and vertical offsets in recent sediments blanketing the Oligocene-Pliocene age carbonate platform are imaged. Zones of offshore deformation, including a fault controlled canyon, appear to be associated with headlands (e.g. Punta Guanajibo), linear NE-SW trending zones of serpentinites and magnetization lows mapped on land. The elongate outcrops of serpentinite in western Puerto Rico are collinear with the recent fault zones we have mapped offshore and suggest that either the presence of serpentinite has localized fault activity or that fault activity has remobilized serpentinite.
AN: T11B-06
TI: Identification of Recent Faulting in Bahia de Añasco and Bahia de Mayagúez, Western Puerto Rico
AU: * Del Greco, L T
EM: delgrecol@uncwil.edu
AF: Center for Marine Science, Univ. of North Carolina, One Marvin K. Moss Lane, Wilmington, NC 28409 United States
AU: Abrams, L J
AF: Center for Marine Science, Univ. of North Carolina, One Marvin K. Moss Lane, Wilmington, NC 28409 United States
AU: Grindlay, N R
AF: Center for Marine Science, Univ. of North Carolina, One Marvin K. Moss Lane, Wilmington, NC 28409 United States
AU: Mann, P
AF: Institute for Geophysics, Univ. of Texas, 4412 Spicewood Lane, Austin, TX 78759 United States
DE: 8150 Plate boundary--general (3040)
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
SC: T
MN: Fall Meeting 2000
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