MODELLO

An overview of the crust and upper mantle structure of the Central America and Caribbean region is presented as a result of the processing of more than 200 seismograms recorded by digital broadband stations from SSSN and GSN seismic networks. By FTAN analysis [1, 2] of the fundamental mode Rayleigh waves, group velocity dispersion curves have been obtained in the period range from 10 s to 40 s; the error of the measurements varies from 0.06 and 0.10 km/s.
From these dispersion curves, seven tomographic maps at different periods and with average spatial resolution of 500 km are obtained. Using the logical combinatorial classification techniques eigth main groups of dispersion curves are determined from the tomographic maps and eleven main regions, each one characterized by one kind of dispersion curves, have been identified. The average dispersion curves obtained for each regionhave been extended to 150 s by adding data from the tomographic study of [3] and they have been inverted using a non-linear procedure. As result of the inversion process, a set of models of the S-wave velocity vs. depth in the crust and upper mantle have been found. In four six regions we identify a typically oceanic crust and upper mantle structure, while in other two the models are consistent with the presence of a continental structure. Two regions, located over the major geological zones of the accretionary crust of the Caribbean region, are characterized by a peculiar crust and upper mantle structure, indicating the presence of lithospheric roots reaching, at least, about 200 km of depth.