Three-dimensional seismic structure of the Leeward Antilles arc from seismic refraction and refraction and reflection tomography
Arogunmati, Adeyemi T.
Zelt, Colin A.; Levander, Alan
Master of Science
We have developed new velocity and Moho interface models for the Dutch Antilles region of the Leeward Antilles arc from independent and simultaneous 3-D inversion of first arrival and PmP traveltimes. The first arrival and PmP traveltimes were picked from wide-angle offshore-onshore seismic data acquired in the Leeward Antilles arc region using 70 offshore and onshore instruments as part of the Broadband Onshore-Offshore Lithosphere Investigation of Venezuela and the Antilles are region (BOLIVAR) experiment. The resulting velocity models show evidence for fault bounded basins and features associated with the under-thrusting of the Caribbean plate beneath South America. Velocities beneath the arc are higher than velocities elsewhere in the study region at all depths and they suggest that the arc may be made of intermediate granulites. Moho interface models vary in depth from 19 km to 37 km in the study area. Beneath the arc, shallow basement topography lies above deep Moho topography and vice versa. In other words, the Moho structure mirrors the basement topography. This observation indicates the possibility of displacement partitioning during the formation of the arc. We compare an average 1-D velocity model from the Leeward Antilles arc to models from other island and continental arcs and find that the Leeward Antilles profile has velocities lower than mafic oceanic island arcs such as the Aleutians, Tonga and the Bonin arc, but has higher velocities than continental arcs such as the Sierra Nevada. Its velocities are however, similar to those of the Honshu island arc. The range of velocities in the Leeward Antilles arc profile is similar to that in the average continental crustal profile. Key words. Leeward Antilles arc, 3D crustal structure, seismic velocity, seismic tomography.
Geology; Geophysics; Earth sciences