Microgravity surveys for geothermal exploration in Tenerife and La Palma islands (Canary Islands)

Gravimetry is a passive geophysical technique that measures variations in the Earth's gravitational field over its surface. This method studies the gravimetric anomalies caused by the presence of heterogeneities in the subsurface, and its values vary depending on the density of the different geological bodies in the subsoil.

This technique has become fundamental in geothermal exploration, providing information on the subsurface density distribution, which allows for constraining underground geological structures. Specifically, it could enable identifying and characterizing gravitational anomalies generated by geothermal resources.

This work is focused on the islands of Tenerife and La Palma, belonging to the Canary Islands. These two islands have been the object of different microgravity studies in recent decades. However, we aim to reach unprecedented detail on some target areas to get a detailed image of the subsurface density distribution. We measured gravity on 109 points in a few target areas of Tenerife and 67 points on the Cumbre Vieja Volcano Complex on the island of La Palma. The precise positioning of the measurement points was realized with a differential GPS (Leica Viva CS10) reaching less than 0.003m of accuracy in the vertical component. Gravity measurements have been realized with a CG-6 Autograv™ gravity meter with a reading resolution of 1 μgal. Every gravity value has been obtained with an average of at least ten measurement cycles of thirty seconds each. This allowed reaching a precision of less than five μgal. Firstly, we got Bouguer anomaly maps of the different target areas of Tenerife and La Palma. Then, we perform inverse modelling to retrieve 3D density models of such regions. Although preliminary, the results reveal a complex geological setting, in accordance with previous geophysical studies

The gravimetric method plays a crucial role in identifying geothermal resources in the Canary Islands. This technique offers perspectives to further develop renewable energies in the Archipelago, fostering a transition towards more sustainable and environmentally friendly energy sources.