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Exploring seismic events on La Réunion: An analysis of rotational sensor and array source directions

Nele I. K. Vesely1 , Eva P. S. Eibl1, Valérie Ferrazzini2,3, Joachim Wassermann4, Zacharie Duputel2,3, Daniel Vollmer1, Christophe Brunet2,3, Frédéric Lauret2,3

  • Affiliations: 1 Institute of Geosciences, University of Potsdam, Potsdam, Germany; 2 Université de Paris, Institut de physique du globe de Paris, CNRS, F-75005, Paris, France; 3 Observatoire volcanologique du Piton de la Fournaise, Institut de physique du globe de Paris, La Plaine des Câfres, Réunion; 4 Department of Earth and Environmental Sciences, Ludwig-Maximilians-University of Munich, Munich, Germany

  • Presentation type: Poster

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

  • Poster Board Number: 131

  • Programme No: 2.1.41

  • Theme 2 > Session 1

Abstract

Indian Ocean island La Réunion hosts the shield volcano Piton de la Fournaise, which lastly erupted in 2023. Besides pre- and co-eruptive signals like volcano-tectonic (VT) earthquakes and eruption tremor, (very) long period events along with rockfalls are seismically recorded. In 2022 we co-installed a rotational sensor to a permanent station of the monitoring network of the Observatoire Volcanologique du Piton de la Fournaise (OVPF) and set up an array of seven additional seismometers within the Enclos-Fouqué caldera. The objective is to compare directions obtained by array processing and new methods using the rotational sensor to the locations from the OVPF's network. To obtain source directions (back azimuths), we apply beamforming on the array data of the vertical component, calculate an orthogonal distance regression between the two horizontal rotational sensor components or determine the correlation between the vertical rotation rate and the horizontal acceleration. We use 37 different events recorded on all instruments and compare the respective calculated back azimuths (BAz) of the array and rotational sensor to the OVPF network catalog location. First results indicate better array than rotational sensor BAz for local earthquakes with respect to the reference direction from the OVPF. For volcanic summit earthquakes however, array and rotational sensor BAz results mostly fall both close to the reference, pointing to the main crater Dolomieu. We assume stronger events generally leading to better source directions and consider topography and local heterogeneities as a cause of diverging results. Following analysis will also include rockfalls as well as thunderstorm events.