This study presents a 3D teleseismic P-wave travel time tomography model along
the Lesser Antilles subduction zone.
Located on the eastern boarder of the Caribbean plate the Lesser Antilles island
arc formed during the last 40 Ma as a consequence of subduction of the relatively
westwards moving North American and South American plates underneath the
The location of the hereby generated triple junction is debated in current re-
search and will be subject of this study.
A joint inversion methodology is applied combining global and regional tomo-
graphic approaches. As an initial model the entire Earth’s mantle in discretized
into spherical blocks with smaller block sizes for the area of investigation.
Ray paths are calculated using a 3D pseudo-bending ray tracing algorithm yield-
ing absolute travel times. They are correlated with absolute velocities of the
subsurface by performing a LSQR inversion.
The data consists of a filtered version of the global EHB catalogue and a manu-
ally processed set of 2604 travel times recorded on OBS stations deployed during
the V oiLA project as well as on permanent land stations in the Caribbean re-
Resolution of the model space is assessed by checkerboard tests and reconstruc-
tion of a synthetic slab model.
The tomographic image of the upper mantle shows a continuous arcuate high
velocity zone ranging from Puerto Rico along the Lesser Antilles island arc to
northeastern Venezuela. This is attributed to the westward subduction of At-
lantic lithosphere beneath the Caribbean plate. In contrast to previous studies
the model does not show a tear in the subducting plate beneath the Lesser
Antilles. Dip angles of the descending plate range from almost vertical in the
southern Lesser Antilles to 40 ◦ - 50 ◦ along the bent of the island arc to 60 ◦ in
the northwestern part. Extensive areas of increased velocity are mapped in the
mantle-transition zone beneath the Caribbean Sea and are attributed to rem-
nants of Proto-Caribbean crust.