Relation Between Volcanic Tremor and Geodetic Strain Signals During Basaltic Explosive Eruptions at Etna

Volcano deformation and seismicity during basaltic explosive eruptions are the expressions of the processes that regulate magma ascent from depth to surface. Both deflation rate and seismic tremor are hypothesized to scale with magma ascent rate, which plays a significant role in the resulting eruptive style. However, the relationship among these quantities has yet to be confirmed on a large number of events. The present study analyzes the seismic and deformation motion retrieved from borehole strainmeter signals recorded during 84 lava fountains at Etna volcano in the period 2012–2023. The very wide frequency range and the high accuracy of the measurements enable: (a) to detect tiny deformation, unachievable with conventional geodetic techniques, and (b) to derive strain tremor unaffected from surface noise. The unprecedented accurate and large data set allows the exploration of the relationship between the seismic and the deformation responses and the extraction of the main features that more accurately reflect the eruptive style as determined by independent volcanological observations. Clustering analyses, conducted separately on the most relevant strain and tremor features, reveal that deformation and seismic responses are not always related each other. A closer examination of the signal evolution indicates that this relationship is not consistent in terms of amplitude or timing. The comparison of the clustering solutions has demonstrated that the strain rate signal is more in accordance with the volcanological classification of the lava fountains with significant impacts for the real‐time characterization and monitoring of basaltic explosive eruptions.