HR: 10:20h
AN: S52A-01    [Abstracts]
TI: Do Fault Intersections Play a Role in Concentrating Seismicity along the Northern Caribbean Plate Boundary? Insights from 2-D Numerical Modeling
AU: Gangopadhyay, A
EM: abhijit@ig.utexas.edu
AF: Institute for Geophysics, University of Texas at Austin, J.J.Pickle Research Campus, Bldg.196, 10100 Burnet Road, Austin, TX 78758, United States
AU: * Pulliam, J
EM: jay@ig.utexas.edu
AF: Institute for Geophysics, University of Texas at Austin, J.J.Pickle Research Campus, Bldg.196, 10100 Burnet Road, Austin, TX 78758, United States
AB: Analytical studies spanning several decades have shown that stresses concentrate at fault intersections and bends when subjected to background tectonic loading. This phenomenon has also been demonstrated in geological systems, both within intraplate (continental and oceanic) and plate boundary settings. In particular, studies of stress interactions between strike-slip faults and the relationship between these stresses and seismicity in the northern Caribbean plate boundary region have produced a better understanding of regional tectonics. In this study we use two-dimensional mechanical modeling to investigate the role of fault intersections in concentrating seismicity along a part of the northern Caribbean plate boundary. We use a numerical method called "Distinct Element Method" implemented by a commercially available code called "UDEC". Our block model comprises of the structural geometry of a part of the northern Caribbean plate boundary spanning Hispaniola and Puerto Rico, and includes the major faults. In our model we use realistic mechanical properties (bulk and shear moduli, and density for the blocks, and stiffnesses, friction, and cohesion for the faults) based on the known geology. Assuming a linear, elastic behavior, we load our model tectonically for a specified period along the direction of the regional plate motion at a rate obtained from GPS studies in the region. At the end of the tectonic loading period we observe the spatial distribution of shear stresses in the model and along the individual faults. We find that relatively high shear stresses are concentrated at the intersections of the Hispaniola and Puerto Rico trenches, Septentrional and Bruce faults, and other fault intersections northeast of Puerto Rico. These locations of relatively high shear stresses also coincide spatially with clusters of seismicity in the region. Some of these fault intersections also have been postulated to be locations of major historical earthquakes. The areas of largest shear stresses also coincide with increased seismicity of greater magnitudes. Our modeling results also predict the appropriate senses of motion along individual faults. Additional, simple three-dimensional analysis is underway to investigate a spatial correlation of the seismicity with depth. These preliminary modeling results demonstrate that fault intersections concentrate stresses when tectonically loaded and influence the spatial distribution of seismicity. Such an analysis has the potential to identify the locations of major earthquakes in the future.
DE: 3070 Submarine landslides
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 7294 Seismic instruments and networks (0935, 3025)
DE: 8107 Continental neotectonics (8002)
DE: 8123 Dynamics: seismotectonics
SC: Seismology [S]
MN: 2007 Joint Assembly