Present-day stress tensors along the southern Caribbean plate boundary zone from inversion of focal mechanism solutions: A successful trial |
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| Institution: | 1. NEXT — Natural and Experimental Tectonics Research Group, Dipartimento di Fisica e Scienze della Terra “Macedonio Melloni”, Università degli Studi di Parma, Italy;2. Eni E&P, Via Emilia 1, I-20097 San Donato Milanese, MI, Italy;1. Renal Hypertension Unit, Division of Nephrology, Department of Medicine, University of Ottawa, Ottawa, Ontario, Canada;2. Ottawa Hospital Research Institute, Ottawa, Ontario, Canada;3. Hypertension Unit, Division of Cardiology, University of Ottawa Heart Institute, Ottawa, Ontario, Canada;1. Grupo de Investigación en Geología y Geofísica (EGEO), Universidad Nacional de Colombia, Medellín, Colombia;2. Departamento de Materiales y Minerales, Universidad Nacional de Colombia, Medellín, Colombia;3. Departamento de Procesos y Energía, Universidad Nacional de Colombia, Medellín, Colombia;4. School of the Environment, Washington State University, Pullman, USA;5. Smithsonian Tropical Research Institute, Balboa, Ancon, Panama;6. Departamento de Ciencias de la Tierra y del Medio Ambiente, Universidad de Alicante, Spain;1. University of Catania, Department of Biological, Geological and Environmental Sciences, Corso Italia, 57, Catania 95129, Italy;2. Consiglio Nazionale delle Ricerche, Istituto di Geologia Ambientale e Geoingegneria, Via Salaria km 29,300, 00015 Montelibretti, Rome, Italy |
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| Abstract: | This paper presents a compilation of 16 present-day stress tensors along the southern Caribbean plate boundary zone (PBZ), and particularly in western and along northern Venezuela. As a trial, these new stress tensors along PBZ have been calculated from inversion of 125 focal mechanism solutions (FMS) by applying the Angelier & Mechler's dihedral method, which were originally gathered by the first author and published in 2005. These new tensors are compared to those 59 tensors inverted from fault-slip data measured only in Plio-Quaternary sedimentary rocks, compiled in Audemard et al. (2005), which were originally calculated by several researchers through the inversion methods developed by Angelier and Mechler or Etchecopar et al.The two sets of stress tensors, one derived from geological data and the other one from seismological data, compare very well throughout the PBZ in terms of both stress orientation and shape of the stress tensor. This region is characterized by a compressive strike-slip (transpressional senso lato), occasionally compressional, regime from the southern Mérida Andes on the southwest to the gulf of Paria in the east. Significant changes in direction of the maximum horizontal stress (σH = σ1) can be established along it though. The σ1 direction varies progressively from nearly east-west in the southern Andes (SW Venezuela) to between NW-SE and NNW-SSE in northwestern Venezuela; this direction remaining constant across northern Venezuela, from Colombia to Trinidad. In addition, the σV defined by inversion of focal mechanisms or by the shape of the stress ellipsoid derived from the Etchecopar et al.'s method better characterize whether the stress regime is transpressional or compressional, or even very rarely trantensional at local scale.The orientation and space variation of this regional stress field in western Venezuela results from the addition of the two major neighbouring interplate maximum horizontal stress orientations (σH): roughly east-west trending stress across the Nazca-South America type-B subduction along the pacific coast of Colombia and NNW-SSE oriented one across the southern Caribbean PBZ. Meanwhile, northern Venezuela, although dextral strike-slip (SS) is the dominant process, NW-SE to NNW-SSE compression is also taking place, which are both also supported by recent GPS results. |
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| Keywords: | Stress tensor Fault-slip data Quaternary tectonics Focal mechanism solution (FMS) Caribbean Venezuela |
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