HR: 16:50h
AN: T24A-03    [Abstracts]
TI: Estimating the Threat of Tsunamigenic Earthquakes and Earthquake Induced-Landslide Tsunami in the Caribbean
AU: * McCann, W R
EM: wrmccann@comcast.net
AF: Earth Scientific Consultants, 10210 West 102nd Avenue, westminster, co 80021, United States
AB: Deformation along the margin of the Caribbean Plate is the principal cause of the tsunami threat in the Caribbean. That margin parallels the northern coast of South America, the Eastern side of the Lesser Antilles, and extends along the Greater Antilles from Puerto Rico through Jamaica. The eastern boundary of the Caribbean plate near the Lesser Antilles is the locus of subduction of Atlantic seafloor. At least three distinct, shallow tectonic regimes parallel that margin. They are: an outer tectonic belt where the North/South America Plate bends to enter the subduction zone, the zone of contact between the plates, and an inner zone of intraplate activity in the overriding Caribbean Plate. The level of seismic activity and tsunami potential in each of these zones is influenced by the presence of rough seafloor on the downgoing plate. Aseismic Ridges may increase the probability slow earthquakes by changing the physical characteristics of the base of the accretionary prism. The northeastern corner of the Caribbean Plate margin undergoes a smooth transition from the relatively simple head-on subduction zone in the N. Lesser Antilles into a region of oblique convergence to the west. It is a complex margin dominated by microplate tectonics from near Puerto Rico through Hispaniola. Here too the same three tectonic zones can be defined, but the third zone, "intraplate activity in the Caribbean Plate", is more clearly delineated as microplate deformation in a wide plate boundary zone. Strike-slip tectonics dominates from Haiti westward to northern Honduras. Local bends in the transcurrent fault systems lead to vertical tectonics in the form of push-up and pull-aparts. Other potential sources lie along the northern coast of S. America and off the east coast of C. America. Manipulation of gridded bathymetry to produce maps of seafloor slope, slope direction, and residual bathymetry, aid the identification of potential slides/slumps, or reveal portions of subduction zones more likely to produce slow earthquakes. Subduction of rough seafloor may activate thrust faults within the accretionary prism above the main decollement, causing indentation of the prism toe. Later reactivation of a dormant decollement would enhance the possibility of slow earthquakes. Subduction of significant seafloor relief and corresponding indentation of the accretionary prism toe would then be another parameter to estimate the likelihood of slow earthquakes. Using these criteria, several regions of the Northeastern Caribbean stand out as more likely sources for slow earthquakes.
DE: 3045 Seafloor morphology, geology, and geophysics
DE: 3060 Subduction zone processes (1031, 3613, 8170, 8413)
DE: 3070 Submarine landslides
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
SC: Tectonophysics [T]
MN: 2007 Joint Assembly