More Than Shaking: What Rotations and Strain Reveal About Volcanic Unrest at Mt. Etna

Monitoring volcanic unrest at complex volcanoes such as Mt. Etna remains challenging due to the coexistence of diverse seismic sources, including volcano-tectonic (VT) earthquakes, sustained tremor and strong scattering in heterogeneous structures. Traditionally, such processes are investigated using translational seismometers alone, potentially limiting the characterization of the underlying wavefield and its physical interpretation.

In this study, we explore the added value of combining translational, rotational, and distributed dynamic strain sensing (DDSS) observations to investigate seismic activity during the December 2025/ January 2026 eruptive activity of Mt. Etna. We analyze six-component ground-motion recordings from a rotational sensor co-located with a conventional seismometer, complemented by DDSS measurements along a nearby fiber-optic cable. Using root-mean-square (RMS) amplitude analyses we examine the temporal evolution of seismic energy associated with tremor and VT activity across the different sensing modalities.

Preliminary results indicate that rotational and translational measurements capture complementary aspects of the volcanic wavefield, with rotational data emphasizing continuous, wavefield-dominated energy components, while translational recordings highlight both impulsive and sustained signals. DDSS observations provide dense spatial sampling, offering additional constraints on signal coherence, propagation characteristics, and source localization. When analyzed jointly, these datasets reveal a more coherent and interpretable picture of volcanic unrest than any single sensor type alone.

Our observations suggest that multi-sensor seismic monitoring, integrating translational, rotational, and DDSS measurements, is particularly advantageous in complex volcanic environments where scattering, anisotropy, and mixed source processes complicate traditional analyses. This work highlights the potential of such integrated approaches for improving the detection, characterization, and interpretation of volcanic seismicity and motivates their broader application in future volcano monitoring strategies.