TY - JOUR T1 - Subduction in the southern Caribbean: Images from finite-frequency P wave tomography JF - Journal of Geophysical Research: Solid Earth Y1 - 2010 A1 - Bezada, M. J. A1 - Levander, A. A1 - Schmandt, B. KW - P-wave tomography KW - southern Caribbean KW - subduction AB - The eastern boundary of the Caribbean plate is marked by subduction of the Atlantic under the Lesser Antilles. The southeastern plate boundary is characterized by a strike-slip margin, while different configurations of subduction of the southwest Caribbean under South America have been proposed. We investigate the slab geometry in the upper mantle using multiple-frequency, teleseismic P wave tomography. Waveforms from P and PKPdf phases from 285 (Mb > 5.0) events occurring at epicentral distances from 30° to 90° and greater than 150° were bandpass filtered and cross-correlated to obtain up to three sets of delay times for each event. The delay times were inverted using approximate first Fresnel zone sensitivity kernels. Our results show the subducting Atlantic slab, as well as a second slab in the west of the study area that we interpret as a subducting fragment of the Caribbean plate. Both slabs have steep dips where imaged and can be traced to depths greater than 600 km. These results are consistent with transition zone boundary topography as determined by receiver function analysis. The Atlantic slab extends continent-ward south of the plate bounding strike-slip margin. We interpret this extension as continental margin lithospheric mantle that is detaching from beneath South America and subducting along with the oceanic Atlantic slab. The steep subduction of the Caribbean occurs ∼500 km landward from the trench, implying an initial stage of shallow subduction as far to the east as the Lake Maracaibo-Mérida Andes region, as has been inferred from intermediate depth seismicity. VL - 115 UR - https://onlinelibrary.wiley.com/doi/abs/10.1029/2010JB007682 N1 - _eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2010JB007682 ER - TY - JOUR T1 - Identification and tectonic implications of a tear in the South American plate at the southern end of the Lesser Antilles JF - Geochemistry, Geophysics, Geosystems Y1 - 2008 A1 - Clark, S. A. A1 - Sobiesiak, M. A1 - Zelt, C. A. A1 - Magnani, M. B. A1 - Miller, M. S. A1 - Bezada, M. J. A1 - Levander, A. KW - jelly sandwich KW - lithospheric detachment KW - mantle dynamics KW - slab break-off KW - STEP KW - tear AB - In the southeast corner of the Caribbean, westward subduction of (Atlantic) oceanic South America beneath the Lesser Antilles transitions to east-west transform motion between continental South America and the Caribbean plate. This geometry requires negatively buoyant, subducting, oceanic South American lithosphere to progressively detach from positively buoyant, continental South American lithosphere. The most widely accepted model is slab break-off, with oblique arc-continent collision and northwest dipping, continental subduction precipitating narrow rifting in the subducting slab. In contrast, the subduction-transform edge propagator (STEP) model conceptualizes progressive detachment along a vertical, dip-slip tear through the lithosphere, with stress focused at the edge of the propagating transform boundary. We present four types of seismic data to resolve the ongoing lithospheric detachment: local seismicity, receiver functions, wide-angle seismic velocity inversion, and a regional, balanced cross section constrained by petroleum industry data. These four data sets image a near-vertical tear extending through the entire lithosphere, revealing a key mechanism for the structural evolution of Venezuela. VL - 9 UR - https://onlinelibrary.wiley.com/doi/abs/10.1029/2008GC002084 N1 - _eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2008GC002084 ER -