Accurate Hypocenter Determination in Lesser Antilles Region from the Sismantilles I Experiment

Abstract

In this study, we present results of the investigation programme SISMANTILLES I, conducted from November 1999 to January 2002, on the Lesser Antilles Arc. We analyzed seismicity by using the data recorded by a combined on- and offshore network that integrated the local volcano-seismological observatories of the Institut de Physique du Globe de Paris (IPGP). The SISMANTILLES I landward network comprised 43 three-component temporary stations. To improve azimuth coverage in earthquake location, it was complemented by 31 OBS. A data-set of 155 well located earthquakes has been used to study the relationship between tectonic structures and seismicity. In particular, to obtain precise hypocenter locations, we applied the concept of minimum 1D model which incorporates the iterative simultaneous inversion of velocity and hypocenter parameters. To partly estimate the huge structural heterogeneity of the Lesser Antilles Subduction Zone, the minimum 1D model is complemented by station corrections which take into account near surface velocity heterogeneity. The relocated hypocenters improve our knowledge on the subduction zone since they have smaller uncertainties with respect to the permanent array locations. The vertical depth sections, perpendicular to the arc, will help define the slab structure and the dip angle.