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How does a dike open? Insight from seismic source modelling of the earthquakes preceding the 2021 Tajogaite eruption (La Palma, Canary Islands).

Luca D'Auria1,2, Aarón Álvarez Hernández1, David Martínez van Dorth1,2, Germán D. Padilla1,2, Rubén García-Hernández1, Víctor Ortega Ramos1, Nemesio M. Pérez1,2 , Aldo Zollo3

  • Affiliations: 1Instituto Volcanológico de Canarias (INVOLCAN), Puerto de la Cruz, Tenerife, Canary Islands 2Instituto Tecnológico y de Energías Renovables (ITER), Granadilla de Abona, Tenerife, Canary Islands  3Università degli Studi di Napoli \"Federico II\", Dipartimento di Fisica \"Ettore Pancini\", Napoli, Italt

  • Presentation type: Talk

  • Presentation time: Friday 15:45 - 16:00, Room S160

  • Programme No: 2.1.12

  • Theme 2 > Session 1

Abstract

The 19th Sept. 2021 eruption of the Cumbre Vieja volcano (La Palma, Canary Islands) was preceded by a week of intense seismicity. Hypocenters migrated westward and upward, following the path of bent and twisted dike. During the precursory phase, earthquakes reached a magnitude up to 3.4; however, in the morning of Sunday, 19th Sept. 2021, just a few hours before the eruption onset, a magnitude 4.1 earthquake shook the island and marked the opening of eruptive vents. In this work, we analyse the mechanism of these precursory earthquakes using a finite fault model with an elliptical geometry. We model the full wavefield using a discrete wavenumber approach (Axitra software), parametrising individual seismic sources using a grid of point sources. We apply this methodology to a selected subset of earthquakes with magnitudes higher than 3.0 and show how the fault geometry and mechanics relate to the local crustal structure and the dike propagation dynamics. In particular, we focus our analysis on the vent opening phase, showing the relationship between local volcano-tectonic dynamics and the earthquake mechanism.