Comparison of a rotational sensor and an array on Piton de la Fournaise volcano, La Réunion

Abstract

Piton de la Fournaise is a shield volcano located on La Réunion island in the Indian Ocean and most recently tends to erupt once - twice annually. Besides volcanic tremor during eruptions and rockfall, long-period (LP) and volcano-tectonic (VT) earthquakes are dominating signals on the island.In October 2022, a rotational sensor and an array of seven seismometers were installed within the Enclos Fouqué, the youngest caldera of volcano Piton de la Fournaise. We record volcano-seismic signals that were also detected by the seismic network of the Observatoire Volcanologique du Piton de la Fournaise (OVPF). Our aim is to test the performance of the rotational sensor and the conventional seismic array with respect to these events.Local VT and rockfall events have been detected on all instruments and could be compared by calculations of backazimuth (BAZ) and signal-to-noise ratio (SNR). We derive the rotational rate using three array stations for array derived rotation (ADR). First results indicate an agreement between the BAZ obtained from the rotational sensor, the array and the location using the OVPF network for strong rockfall events. Summit VT and weak local earthquakes could furthermore be located by the array BAZ. Preliminary SNR results from all considered events indicate higher values for the array stations. Since the instruments could not be buried on site and the rotational sensor is likely affected by wind noise, it is assumed that comparison between the instruments will work best for strong and/ or close events.