Comparison of rotational sensor and array-derived back azimuths with network locations of LP events and tremor on Etna volcano, Italy

Etna volcano is one of Europe’s most active volcanoes in proximity to a densely inhabited and touristic area, which leads to the urge of understanding its behaviour and patterns. A seismic experiment has been set up on Etna volcano in 2019 including an array of seismometers, a rotational sensor and a distributed acoustic sensing (DAS) cable. Previous research of Eibl et al. (2022) has compared the rotational sensor’s back azimuths of long-period (LP) events and tremor on Etna volcano, Italy, with localizations from the Istituto Nazionale di Geofisica e Vulcanologia-Osservatorio Etneo (INGV-OE) network. Here, we are now comparing the back azimuths of a small aperture array around the rotational sensor with previous results for LP events and tremor of one day during the experiment. First results show the best agreement between the INGV-OE localizations and the array’s horizontal North components for LP event arrival. However, the rotational sensor back azimuth median seems to generally fit better to the network localizations during the entire event. Tremor INGV-OE localizations are best fit by back azimuths derived using the horizontal East component of the array with around 2° deviation in the mean, whereas the rotational sensor back azimuths differ around 10°. Reasons for the discrepancy with the expected location is currently in discussion. Rotational sensors facilitate field work and enhance wave field understanding. For which wave types and settings the back azimuth results by the rotational sensor are fitting better to the expectations than those of an array is still to be confirmed.   Reference: Eibl, E. P. S., Rosskopf, M., Sciotto, M., Currenti, G., Di Grazia, G., Jousset, P., et al. (2022). Performance of a rotational sensor to decipher volcano seismic signals on Etna, Italy. Journal of Geophysical Research: Solid Earth, 127, e2021JB023617. https://doi.org/10.1029/2021JB023617