Lithospheric rheology and strength in La Palma Island (Canary archipelago)

The Canary Islands are an archipelago of eight islands and several islets in the Atlantic Ocean that have been built up by intraplate magmatism. The more recent subaerial eruption took place in La Palma Island during the last four months of 2021 (September 19^th to December 13^th). This volcanic activity formed the Tajogaite volcanic vent and several minor vents following an eruptive fissure roughly trending N310ºE. The eruption was preceded by intense shallow (<12 km depth) volcanotectonic activity that continued during the whole eruptive process, reaching more than 11,000 earthquakes located. After the first shallow pre-eruptive seismic swarm, the seismicity was mainly located at two different depth levels with hypocenters located at 10-15 and 30-40 km depth.

Seismicity record in the island for previous historical eruptions is very scarce and we have used this seismic episode to explore the lithospheric strength in this intraplate geodynamic setting corresponding to an old (~156 Ma) oceanic lithosphere. Geotherms and brittle and ductile rheological laws with different thermo-mechanical properties have been used to calculate strength envelopes. We have combined the study of the lithospheric strength and the vertical distribution of the seismicity from that period to estimate the extension of the brittle mechanical layer that conditioned the hypocentral locations.