1,1,1,4,5,4,5- 1Institute of Geosciences, University of Potsdam, Potsdam, Germany (vesely1@uni-potsdam.de)
- 2Department of Earth and Planetary Sciences, University of California Davis, Davis, CA, USA
- 3Department of Earth Sciences, University of Oregon, OR, USA
- 4Université de Paris Cité, Institut de physique du globe de Paris, CNRS, F-75005, Paris, France
- 5Observatoire volcanologique du Piton de la Fournaise, Institut de physique du globe de Paris, La Plaine des Câfres, Réunion
Piton de la Fournaise volcano on La Réunion island is a shield volcano that showed annual eruptive behavior since 2014. Following the last eruption of this eruptive cycle in 2023, only seismic crises were detected, but no eruption occurred until the time of writing, making the analysis of the 2023 eruption especially important. The 2023 eruption of Piton de la Fournaise volcano began on 2 July with two fissure openings on the northeastern flank, followed by a third eruptive vent on the southeastern flank that lasted until 10 August. We analyze data from a temporary seismic array on the western flank within Enclos Fouqué Caldera and the permanent network from the Volcanological Observatory of Piton de la Fournaise (OVPF-IPGP) to investigate the eruption dynamics.
The tremor frequency range varies slightly between the three fissure activity periods but is mostly concentrated between 0.8 and 4 Hz. Tremor amplitude and GNSS measurements at the summit crater show similar changes for the start and towards the end of the eruption as previously observed at the volcano. While the network analysis provides highly accurate locations for the three distinct fissures, we only obtain well fitting back azimuths (BAz) for specific times from the seismic array. Slowness results from the array however help distinguish the tremor signal into surface and body waves, and for certain phases even indicate the existence of two distinct tremor sources.
The deviating array back azimuths that are observed for the surface waves are interpreted to be related to the medium heterogeneity within the crater region including topographic effects. Our preliminary results, combining two different methods allow the determination of two tremor signals for one fissure site that exhibit different frequency ranges and amplitudes and possibly originate from both subsurface and surface sources. We assume that surface activity is dominating the analysis, but once decreased, a weaker tremor signal at depths becomes visible.
How to cite: Ohrnberger, M., Vesely, N. I. K., Eibl, E. P. S., Journeau, C., Duputel, Z., Vollmer, D., Brunet, C., Lauret, F., and Ferrazzini, V.: First insights into the 2023 Piton de la Fournaise eruption: Revealing two distinct tremor signals, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10978, https://doi.org/10.5194/egusphere-egu26-10978, 2026.
