Spatial variations in crustal and mantle anisotropy across the North American‐Caribbean boundary on Haiti
Spatial variations in crustal and mantle anisotropy across the North American‐Caribbean boundary on Haiti
Haiti, on the island of Hispaniola, is situated across the North American-Caribbean plate boundary at the transition point between oblique subduction in the east and a transform plate boundary in the west. Here we use shear wave splitting measurements from S waves of local (0–50 km) and intermediate depth (50–150 km) earthquakes as well as SK(K)S phases from teleseismic earthquakes to ascertain good spatial and vertical resolution of the azimuthal anisotropic structure. This allows us to place new constraints on the pattern of deformation in the crust and mantle beneath this transitional region. SK(K)S results are dominated by plate boundary parallel (E-W) fast directions with ~1.9 s delay times, indicating subslab trench parallel mantle flow is continuing westward along the plate boundary. Intermediate depth earthquakes originating within the subducting North American plate show a mean fast polarization direction of 065° and delay time of 0.46 s, subparallel to the relative plate motion between the Caribbean and North American plates (070°). We suggest a basal shear zone within the lower ductile crust and upper lithospheric mantle as being a potential major source of anisotropy above the subducting slab. Upper crustal anisotropy is isolated using shear wave splitting measurements on local seismicity, which show consistent delay times on the order of 0.2 s. The fast polarization directions indicate that the crustal anisotropy is controlled by the fault networks in close proximity to the major strike-slip faults, which bisect the north and south of Haiti, and by the regional stress field where faulting is less pervasive.
Caribbean, Haiti, anisotropy, plate boundary, shear wave splitting
Possee, Daniel, James
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Keir, Derek
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Harmon, Nicholas
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Rychert, Catherine
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Eakin, Caroline M
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Rolandone, Frédérique
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Leroy, Sylvie
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Corbeau, Jordane
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Stuart, Graham
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Boisson, Dominique
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Momplaisir, Roberte
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Prépetit, Claude
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1 June 2020
Possee, Daniel, James
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Keir, Derek
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Harmon, Nicholas
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Rychert, Catherine
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Eakin, Caroline M
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Rolandone, Frédérique
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Leroy, Sylvie
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Corbeau, Jordane
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Stuart, Graham
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Boisson, Dominique
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Momplaisir, Roberte
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Prépetit, Claude
6ab89f7a-2d0c-4247-a5e4-0ab688864c8c
Possee, Daniel, James, Keir, Derek, Harmon, Nicholas, Rychert, Catherine, Eakin, Caroline M, Rolandone, Frédérique, Leroy, Sylvie, Corbeau, Jordane, Stuart, Graham, Boisson, Dominique, Momplaisir, Roberte and Prépetit, Claude
(2020)
Spatial variations in crustal and mantle anisotropy across the North American‐Caribbean boundary on Haiti.
Journal of Geophysical Research, 125 (6), [e2019JB018438].
(doi:10.1029/2019JB018438).
Abstract
Haiti, on the island of Hispaniola, is situated across the North American-Caribbean plate boundary at the transition point between oblique subduction in the east and a transform plate boundary in the west. Here we use shear wave splitting measurements from S waves of local (0–50 km) and intermediate depth (50–150 km) earthquakes as well as SK(K)S phases from teleseismic earthquakes to ascertain good spatial and vertical resolution of the azimuthal anisotropic structure. This allows us to place new constraints on the pattern of deformation in the crust and mantle beneath this transitional region. SK(K)S results are dominated by plate boundary parallel (E-W) fast directions with ~1.9 s delay times, indicating subslab trench parallel mantle flow is continuing westward along the plate boundary. Intermediate depth earthquakes originating within the subducting North American plate show a mean fast polarization direction of 065° and delay time of 0.46 s, subparallel to the relative plate motion between the Caribbean and North American plates (070°). We suggest a basal shear zone within the lower ductile crust and upper lithospheric mantle as being a potential major source of anisotropy above the subducting slab. Upper crustal anisotropy is isolated using shear wave splitting measurements on local seismicity, which show consistent delay times on the order of 0.2 s. The fast polarization directions indicate that the crustal anisotropy is controlled by the fault networks in close proximity to the major strike-slip faults, which bisect the north and south of Haiti, and by the regional stress field where faulting is less pervasive.
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2019JB018438
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Accepted/In Press date: 5 May 2020
e-pub ahead of print date: 9 May 2020
Published date: 1 June 2020
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Funding Information:
The work contained in this paper contains work conducted during a PhD study undertaken as part of the Natural Environment Research Council (NERC) Centre for Doctoral Training (CDT) in Oil and Gas (Grant NE/M00578X/1). It is 50% funded by Southampton University via their Graduate School of the National Oceanography Centre Southampton (GSNOCS) and 50% funded by NERC both of whose support is gratefully acknowledged. We thank Seismic Equipment Infrastructure in the UK (SEIS-UK) for the use of the instruments and their computing facilities. The facilities of SEIS-UK are supported by NERC under Agreement R8/H10/64. C. A. R. and N. H. acknowledge funding from NERC (NE/M003507/1 and NE/K010654/1) and the European Research Council (GA 638665). C. M. E. is supported by the Australian Research Council (DE190100062). S. L., F. R., and J. C. acknowledge full support from the Insitut des Sciences de la Tere Paris (ISTeP) to the Trans-Haiti project. We thank the Unit? Technique de Sismologie of the Bureau des Mines et de l'Energie, and the URGeo of the Universit? d'Etat d'Haiti for their help in the field. We thank Kelly Guerrier, Sophia Ulysse, and Frantz Saint Preux for their active contribution in installing the seismic stations and collecting the data. We also thank Tom Hall for his involvement in the fieldwork and data processing. Figures were made with the aid of the Generic Mapping Tools (Wessel et al.,?2013). Data for the Trans-Haiti Network (https://www.fdsn.org/networks/detail/ZU_2013/), Canadian National Seismograph Network (https://doi.org/10.7914/SN/CN), and Caribbean USGS Network (https://doi.org/10.7914/SN/CU) can be downloaded from the Incorporated Research Institutions for Seismology Data Management Center (IRIS-DMC; https://ds.iris.edu/ds/nodes/dmc/). Teleseismic and intermediate depth earthquake were downloaded from the Advanced National Seismic System Comprehensive Catalog (ANSS ComCat; https://doi.org/10.5066/F7MS3QZH).
Publisher Copyright:
© 2020. The Authors.
Keywords:
Caribbean, Haiti, anisotropy, plate boundary, shear wave splitting
Identifiers
Local EPrints ID: 441085
URI: http://eprints.soton.ac.uk/id/eprint/441085
ISSN: 0148-0227
PURE UUID: 4420ded8-578e-4f39-8825-185cff64e7d0
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Date deposited: 29 May 2020 16:31
Last modified: 17 Mar 2024 03:24
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Contributors
Author:
Daniel, James Possee
Author:
Caroline M Eakin
Author:
Frédérique Rolandone
Author:
Sylvie Leroy
Author:
Jordane Corbeau
Author:
Graham Stuart
Author:
Dominique Boisson
Author:
Roberte Momplaisir
Author:
Claude Prépetit
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