The seismicity of the Madeira archipelago – hints for active volcanism and/or tectonic faults?

• Main Authors: Krüger, F., Heimann, S., Custodio, S., Silveira, G., Matias, L., Schlaphorst, D.
• Format: Conference Object
• Language: English
• Published: 2023
• Subjects: Main Island; Northeast Atlantic
• Online Access: https://gfzpublic.gfz-potsdam.de/pubman/item/item_5019645

Madeira is discussed to be a hotspot volcanic complex in the Northeast Atlantic placed on 140 Ma old oceanic lithosphere. Catalog seismicity beneath and around Madeira is sparse and hypocenters are often not well constrained due to lack of station coverage. In 2020 and 2022 two events with Mw 5.3 and Mw 4.9 were widely felt on the island. We used data of a local seismic network consisting of 24 temporary stations in the years 2011-2012 and up to 4 permanent stations to reveal the local seismicity in the Madeira archipelago. We used an adapted velocity model and the LASSIE detection software and found more than 220 additional events, which we located using HYPOSAT. Most of the events concentrate about 30-40 km south of the main island with hypocenter depths in the range of 20 up to 40 km. The seismicity stops at the south coast of Madeira and starts again north of the main island. Other zones of activity are found in the East of Madeira and in the vicinity of Desertas Grande island southeast of Madeira. Hypocenter depths beneath Madeira cluster between 10 and 20 km depth at Moho or sub-Moho level. Our data support the hypothesis that the center of volcanic activity in the archipelago might nowadays be associated with the southern end of the Funchal Ridge.