Lesser Antilles instrumental seismic catalog from the French observatories for seismic hazard assessment

With the upcoming adoption of a new version of the European construction codes, the French agency for risk mitigation (DGPR) has initiated the update of the probabilistic seismic hazard assessment (PSHA) on its territories. For the French Lesser Antilles territories of Martinique, Guadeloupe, Saint-Martin and Saint-Barthélémy islands, this PSHA update is done in the framework of the ATLAS project. Long period and broad coverage seismic catalogs with homogeneous magnitude estimates are needed as input in PSHA calculation. In the French Antilles, IPGP volcanological and seismological observatories in Martinique (OVSM) and Guadeloupe (OVSG) locate all events seen by their seismic networks since 1981. In 2013, in the framework of the CDSA regional project (centre de données sismologique des Antilles), Massin et al has merged all phases bulletin and location from different agencies, including OVSM and OVSG to produce a multi-origin, automatic relocated catalog available in QuakeML format.

Since 2014 and the completion of the WI VSAT regional network, IPGP publishes every year a validated and unique catalog with the data from both IPGP observatories. In 2025, this catalog between 2014  and 2022 was processed by Gonzalez et al to compute moment magnitudes and establish robust regression laws between Mw and the most commonly used local magnitude scales in OVSM and OVSG.

Based on those two previous studies, we were able to retrieve the original manually validated OVSM and OVSG catalogs from the CDSA database in QuakeML format. We then applied the same validation process we are using to produce the unique yearly catalog since 2014. This process includes identifying and merging events that were located by both observatories, selecting the best solution. A thorough manual review is performed to eliminate any false or badly located event and to ensure no significant events were missed. All events without any magnitude are removed from the database.

Prior to 2013, only one magnitude was used in routine at the observatory, consistently since 1981: the duration magnitude. However, for significant events, this magnitude which saturates around M 4 was replaced by local or moment magnitude from international agencies. For events with magnitude higher than 4, we then look in the ISC earthquake database to replace the local magnitude by GCMT Mw magnitude if it exists, or to tag the observatory magnitude as local. Finally, we apply the regression laws established by Gonzalez et al to produce a final catalog with all magnitude either in calculated Mw or in converted Mw.

This validated catalog of more than 30 000 events covers the central portion of the Lesser Antilles between 1981 and 2013. In addition to the PSHA studies performed in the framework of the ATLAS project, this reference catalog can be used for numerous studies, such as long-term seismo-tectonic variations of the subduction and crustal faults.