Geothermal survey using earthquake seismic tomography in La Soufrière, Guadeloupe

La Soufrière volcano, located in the volcanic island of Guadeloupe, has virtually unlimited geothermal resources. The intense seismic activity of the volcanic system allows the application of passive seismic methods to explore the geothermal potential in the area. The high seismic activity in the volcano, together with the well-developed network of tectonic faults mapped at La Soufriere facilitates the upwelling of geothermal fluids in the upper crust.

This study aims to image the shallow seismic velocity structure of the volcano by deriving a Local Earthquake Tomography with data from a dense network of 48 three-component short-period nodal geophones deployed in October 2023 around the volcanic massif, complemented by 8 permanent seismic stations operated by the IPGP.

We first built a seismic catalogue by applying a machine-learning seismic phase picker PhaseNet, for which we initially obtained 551,383 P- and S-wave phases. We detected 339 seismic events with PyOcto and successfully located 145 events with NonLinLoc. The seismic catalogue was the input of a Local Earthquake Tomography using our relocated catalogue to develop a high-resolution model of the volcanic system. We produced an interpretation of the subsurface structure based on the distribution of Vp, Vs and Vp/Vs ratio velocity anomalies. This model will highlight fractures and conduits that enable the circulation of hydrothermal fluids, and the different volcanic structures. Our results will be compared with ongoing studies of the volcanic system, such as Ambient Noise Tomography and Tremor relocation, to refine our interpretation of the shallow plumbing system of this active volcano. This work will contribute to the monitoring of the volcano and support geothermal exploration efforts in the region.