Probing layered arc crust in the Lesser Antilles using receiver functions

Abstract

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.

Eocene intra-plate shortening responsible for the rise of a faunal pathway in the northeastern Caribbean realm

“…Offshore seismic profiles and gravity data were acquired during the GARANTI cruise west of St. Barthélemy, around and on the Saba Bank, in the Lesser Antilles arc, and backarc area (S2 File) (Fig 3). We provide a 2D model of gravity data (S3 File) that gives a 40 km crustal thickness below the Lesser Antilles forearc, which is consistent with previously published data (30,31) (Fig 4A and 4B). We correlated the seismic stratigraphy correlated with the stratigraphy constrained in the SB2 petroleum well [40] (Fig 3A).…”

“…In the north, however, the seafloor topography is rough, its mean bathymetry is -1400 m, and the Moho is deeper, ~25 km [ 28 , 29 ]( Fig 1C ). The Moho beneath the present-day arc and the fore-arc even reaches 29–38 km depth in northern Lesser Antilles [ 30 , 31 , 37 ]. ( Fig 1C ).…”

“…PR, VI, AR, GB and CLIP, Car, Sam, Nam stand for, Puerto-Rico, Virgin Island, Aves Ridge, Grenada Basin, Caribbean Large Igneous Province, Caribbean plate, South American plate and North America plate, respectively. C) Map of the Lesser Antilles showing the Aves Ridge, Grenada Basin, Lesser Antilles and crustal thickness (iso-contours from gravity modeling after [ 28 , 29 ]; white dots: Moho depth estimates based on receiver function inversions from [ 30 , 31 ]). Figure made with GeoMapApp ( www.geomapapp.org ) / CC BY [ 32 ].…”

Deep Structure of the Grenada Basin From Wide‐Angle Seismic, Bathymetric and Gravity Data

“…It has very similar characteristics to Aves Ridge, however its thickness does not exceed 25 km, which is in good agreement with earlier wide‐angle seismic studies (C. B. Officer et al., 1957; Boynton et al., 1979; Kopp et al., 2011), petrology of crustal xenoliths and seismic receiver functions (Melekhova et al., 2019) and receiver function studies (Gonzalez et al., 2018; Schlaphorst et al., 2018; Sevilla et al., 2010), which show variable thicknesses between 25 and 35 km thick crust along the active arc. The velocity‐depth curves from the Aves Ridge and the LAA and forearc region show that seismic velocities in both structures are similar (Figure 15) indicating that the composition of rocks might be similar in both regions.…”

Inferring Interseismic Coupling Along the Lesser Antilles Arc: A Bayesian Approach

“…Crustal structure showing P-wave velocity (V P ), S-wave velocity (V S ) and density as a function of depth. The solid lines represent the model used in this study (based onSchlaphorst et al [2018]). Shaded areas represent a 15% uncertainty region.…”