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Double subduction beneath Hispaniola? an investigation of earthquakes by body wave inversion

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dc.contributor.advisor Nabelek, John
dc.contributor.advisor Ness, Gordon E.
dc.creator Ludwig, Rainer
dc.date.accessioned 2012-05-14T16:54:35Z
dc.date.available 2012-05-14T16:54:35Z
dc.date.copyright 1989-11-03
dc.date.issued 1989-11-03
dc.identifier.uri http://hdl.handle.net/1957/29148
dc.description Graduation date: 1990 en_US
dc.description.abstract High seismic activity occurs along the Caribbean and the North American Plate boundary beneath the eastern part of Hispaniola. A large number of intermediate to deep earthquakes are clustered between the Puerto Rico Trench to the north and the Muertos Trench to the south suggesting the possibility of concurrent subduction from both north and south. The body wave inversion technique was used to analyze nine earthquakes, the largest teleseismically recorded events since the establishment of WWSSN (World Wide Standardized Seismograph Network) in 1963 in the geographic region between 72°W and 66°W latitude and 16°N and 21°N longitude. Their body-wave magnitude ranges from 5.6 to 6.1. Each event was inverted for strike, dip and slip of the two possible fault planes, as well as for the centroid depth, the total seismic moment and the source time function. In order to optimize the crustal structure parameters used in the body wave inversion method, a two-dimensional geophysical cross-section across Hispaniola was constructed by forward modeling of gravity and magnetics data. The inversion results are consistent and can be divided into groups according to the depth and the epicentral location of the events. The shallow events, with depths of 6 to 12 km, represent crustal deformation and show thrust mechanisms with large strike-slip component. The intermediate depth events range from 42 to 107 km in depth and occur to the south of eastern Hispaniola. They show clear thrust mechanisms with a consistent dip of the compressional P-axis at about 30° to the north and approximately north-south P-axis strike. The deep earthquakes occur between 110 and 177 km depth, have a steep-dipping tensional T-axis, and define another slab, possibly originating at the Puerto Rico Trench to the north. One m[subscript b]=6.l event, which occurred on 6/24/84, shows opposite orientations of the P- and T-axes from the surrounding intermediate events. It is interpreted as an interface event in the upper mantle. The southern subduction zone is well defined and indicates that the Muertos Trench is active, with the subducting plate dipping to the north beneath eastern Hispaniola. At a depth of about 110 km, the northward dipping slab collides with the almost vertical segment of the other slab. This deep vertical slab segment, extending to at least 200 km in depth, may be a remnant of an earlier subduction zone associated with the Puerto Rico Trench. Alternatively, it may be connected with a more gently dipping part of the slab towards the north or, even in some way, with subduction from the south. en_US
dc.language.iso en_US en_US
dc.subject.lcsh Earthquakes -- Hispaniola en_US
dc.subject.lcsh Seismology -- Hispaniola en_US
dc.subject.lcsh Plate tectonics -- Hispaniola en_US
dc.title Double subduction beneath Hispaniola? an investigation of earthquakes by body wave inversion en_US
dc.type Thesis/Dissertation en_US
dc.degree.name Master of Science (M.S.) in Geophysics en_US
dc.degree.level Master's en_US
dc.degree.discipline Oceanic and Atmospheric Sciences en_US
dc.degree.grantor Oregon State University en_US
dc.contributor.committeemember Couch, Richard
dc.contributor.committeemember Levi, Shaul
dc.description.digitization File scanned at 300 ppi (Monochrome) using ScandAll PRO 1.8.1 on a Fi-6770A in PDF format. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR. en_US
dc.description.peerreview no en_us

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