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Abstract:
The characterization of the crustal structure of the plates involved in a subduction system is a crucial step towardsthe understanding of potentially associated geohazards. Despite the low current seismic activity in the Lesserand Leeward Antilles (compared with other subduction zones), several historical M>7 earthquakes have beenregistered in both regions. In the Lesser Antilles, the oceanic floor of the North and South American plates subductsbeneath the Caribbean plate. In contrast, in the Leeward Antilles, the Caribbean plate subducts under the continentalSouth American plate. In regions where the seismic records do not extend far back in time, or where the frequencyof such large earthquakes is low, alternative indirect methods for delimiting seismogenic zones may be applied.In those cases, it would be valuable to characterize in detail the regional continental-oceanic boundary and thebackstop edge location. The tectonic history of the Lesser Antilles includes a variety of allochthonous slightly orhigh buoyant fragments, which have been either subducted or accreted to the backstop, and which can influence thespatial seismicity patterns. Moreover, previous studies suggest that the north central region of the Lesser Antillesforearc is composed of two different crustal units: an inner and an outer forearc domains, characterized by high andlow seismic velocity gradients, respectively. Such crustal domains interact spatially with the down-going plate, forexample, acting as backstops. Nevertheless, the seismic experiments carried out in the Lesser Antilles have focusedonly on a relatively narrow region; thus, much of the structure of the currently active volcanic arc remains poorlyconstrained.
