Gaps, tears and seismic anisotropy around the subducting slabs of the Antilles

Schlaphorst, David; Kendall, J.‐M.; Baptie, Brian; Latchman, Joan L.; Tait, S.

doi:10.1016/j.tecto.2017.01.002

Cited by 25 publications

(35 citation statements)

References 80 publications

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“…Benford et al (2012) proposed a simple model in which mantle anisotropy was dominated by large‐scale lithospheric fabrics associated with the large transform fault zones that bisect the north and south of the island. However, further to the east other studies prefer subslab trench‐parallel mantle flow with an isotropic mantle above (Lynner & Long, 2013; Meighan & Pulliam, 2013;Piñero‐Feliciangeli & Kendall, 2008; Schlaphorst et al, 2017). Both these mechanisms would generate seismic anisotropy with an east to west trending fast polarization direction.…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

“…Studies to the east, in the region of Puerto Rico, suggest the mantle wedge above the slab does not provide a significant anisotropic contribution compared to the subslab mantle (Piñero‐Feliciangeli & Kendall, 2008; Schlaphorst et al, 2017). Schlaphorst et al (2017) observed a mean dt measurment of 0.21 s from seismicity associated with the slab. However, the mean dt we observe at station SDDR for these intermediate earthquakes is 0.46 ± 0.17 s, compared to 0.19 ± 0.09 s for earthquakes originating within the crust (Figure 7).…”

Section: Discussionmentioning

confidence: 99%

“…There have been a number of studies that have focused on the anisotropic structure of the Caribbean‐North American plate boundary, mostly focusing on mantle anisotropy through observations of shear wave splitting from teleseismic earthquakes (Figure 1). In general, fast polarization directions have been found to be parallel to the plate boundary (Benford et al, 2012; Hodges & Miller, 2015; Lynner & Long, 2013; Meighan & Pulliam, 2013; Piñero‐Feliciangeli & Kendall, 2008; Schlaphorst et al, 2017). However, given the lateral segmentation of the plate boundary, differing explanations have been used to explain these observations.…”

Section: Introductionmentioning

confidence: 99%

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Spatial Variations in Crustal and Mantle Anisotropy Across the North American‐Caribbean Boundary on Haiti

et al. 2020

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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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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Spatial Variations in Crustal and Mantle Anisotropy Across the North American‐Caribbean Boundary on Haiti

et al. 2020

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“…The spatial variability in seismicity along the arc has also been attributed to the effects of the subducting fracture zones [20]. The dramatic variations in crustal properties might suggest complicated upper mantle wedge dynamics, which would explain why the seismic properties of the upper mantle wedge beneath the LAA appear to be isotropic [62,63].…”

Section: Discussionmentioning

confidence: 99%

Probing layered arc crust in the Lesser Antilles using receiver functions

et al. 2018

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Oceanic arcs can provide insight into the processes of crustal growth and crustal structure. In this work, changes in crustal thickness and composition along the Lesser Antilles Arc (LAA) are analysed at 10 islands using receiver function (RF) inversions that combine seismological data with vP/vS ratios estimated based on crustal lithology. We collected seismic data from various regional networks to ensure station coverage for every major island in the LAA from Saba in the north to Grenada in the south. RFs show the subsurface response of an incoming signal assuming horizontal layering, where phase conversions highlight discontinuities beneath a station. In most regions of the Earth, the Mohorovičić discontinuity (Moho) is seismically stronger than other crustal discontinuities. However, in the LAA we observe an unusually strong along-arc variation in depth of the strongest discontinuity, which is difficult to explain by variations in crustal thickness. Instead, these results suggest that in layered crust, especially where other discontinuities have a stronger seismic contrast than the Moho, H–k stacking results can be easily misinterpreted. To circumvent this problem, an inversion modelling approach is introduced to investigate the crustal structure in more detail by building a one-dimensional velocity–depth profile for each island. Using this method, it is possible to identify any mid-crustal discontinuity in addition to the Moho. Our results show a mid-crustal discontinuity at about 10–25 km depth along the arc, with slightly deeper values in the north (Montserrat to Saba). In general, the depth of the Moho shows the same pattern with values of around 25 km (Grenada) to 35 km in the north. The results suggest differences in magmatic H2O content and differentiation history of each island.

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