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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
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
0148-0227
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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Possee, Daniel, James
30c7e9de-c298-469e-a9ae-c1c1caf910dc
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Harmon, Nicholas
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Rychert, Catherine
70cf1e3a-58ea-455a-918a-1d570c5e53c5
Eakin, Caroline M
767ea10a-757b-4db5-8705-0c79368f8606
Rolandone, Frédérique
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Leroy, Sylvie
627c503b-1036-41fc-a24c-3d09954fab0a
Corbeau, Jordane
a71d8ba4-f19d-43ac-9c4e-ddcef42ff745
Stuart, Graham
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Boisson, Dominique
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Momplaisir, Roberte
8707114c-90ad-46d3-af3a-10decf89c7ac
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).

Record type: Article

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 - Accepted Manuscript
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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
Additional Information: 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
ORCID for Derek Keir: ORCID iD orcid.org/0000-0001-8787-8446
ORCID for Nicholas Harmon: ORCID iD orcid.org/0000-0002-0731-768X

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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: Derek Keir ORCID iD
Author: Nicholas Harmon ORCID iD
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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