Gravity modeling of the Muertos Trough and tectonic implications (north-eastern Caribbean) |
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Authors: | J L Granja Bruña A Muñoz-Martín U S ten Brink A Carbó-Gorosabel P Llanes Estrada J Martín-Dávila D Córdoba-Barba M Catalán Morollón |
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Institution: | 1.Applied Tectonophysics Group, Departamento de Geodinámica,Universidad Complutense de Madrid,Madrid,Spain;2.United States Geological Survey,Woods Hole,USA;3.Departamento de Física de la Tierra y Astrofísica I,Universidad Complutense de Madrid,Madrid,Spain;4.Real Instituto y Observatorio de la Armada, San Fernando,San Fernando-(Cádiz),Spain |
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Abstract: | The Muertos Trough in the northeast Caribbean has been interpreted as a subduction zone from seismicity, leading to infer
a possible reversal subduction polarity. However, the distribution of the seismicity is very diffuse and makes definition
of the plate geometry difficult. In addition, the compressive deformational features observed in the upper crust and sandbox
kinematic modeling do not necessarily suggest a subduction process. We tested the hypothesized subduction of the Caribbean
plate’s interior beneath the eastern Greater Antilles island arc using gravity modeling. Gravity models simulating a subduction
process yield a regional mass deficit beneath the island arc independently of the geometry and depth of the subducted slab
used in the models. This mass deficit results from sinking of the less dense Caribbean slab beneath the lithospheric mantle
replacing denser mantle materials and suggests that there is not a subducted Caribbean plateau beneath the island arc. The
geologically more realistic gravity model which would explain the N–S shortening observed in the upper crust requires an overthrusted
Caribbean slab extending at least 60 km northward from the deformation front, a progressive increase in the thrusting angle
from 8° to 30° reaching a maximum depth of 22 km beneath the insular slope. This new tectonic model for the Muertos Margin,
defined as a retroarc thrusting, will help to assess the seismic and tsunami hazard in the region. The use of gravity modeling
has provided targets for future wide-angle seismic surveys in the Muertos Margin. |
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