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Advances in the search of an ambient noise tomography model of La Palma Island after the 2021 eruption

Javier Tortosa 1,2, Javier Almendros1,2, Martin Schimmel3

  • Affiliations:  1Departamento de Física Teórica y del Cosmos, Universidad de Granada, Granada, Spain; 2Instituto Andaluz de Geofísica, Universidad de Granada, Granada, Spain; 3Geociencias Barcelona (GEO3BCN), CSIC, Barcelona, Spain 

  • Presentation type: Poster

  • Presentation time: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 15

  • Programme No: 1.5.22

  • Theme 1 > Session 5

Abstract

We study continuous seismic ambient noise recorded by a temporary dense network in La Palma (Canary Islands, Spain) to develop high-resolution velocity models of the uppermost crust. After the 2021 Tajogaite eruption, the IMAGMASEIS project established several dense seismic arrays on the island to enhance our knowledge of its shallow velocity structure. One of these networks includes 37 broadband seismometers provided by GFZ and the University of Granada, alongside 21 permanent stations operated by the Spanish National Geographic Institute (IGN) and the Volcanological Institute of the Canary Islands (INVOLCAN). This network ensures dense coverage of the entire island, with inter-station distances averaging 5 km and a maximum separation of 40 km. Data collection started in September 2023 and ended in October 2024. To estimate Green's functions between station pairs, we stacked cross-correlations of 1-day windows in the time domain over the recording period. We also examined the impact of various preprocessing steps, including spectral whitening and time normalization. Rayleigh-wave dispersion curves were extracted using frequency-time analysis (FTAN), obtaining robust results in the 1 s to 6--7 s period range. Our preliminary findings agree with previous studies, revealing high relative group velocities in the geologically older northern region and lower velocities in the southern area, characterized by historical volcanic activity. These results will be used to perform an inversion and obtain a tomographic model of the island.