Geohazards in the Western Ionian Sea: Insights from non-earthquake signals recorded by the NEMO-SN1 seafloor observatory

Abstract

Seafloor instability resulting from both tectonics and volcanism affects the Western Ionian Sea. The NEutrino Mediterranean Observatory-Submarine Network 1 (NEMO-SN1), deployed 25 km offshore eastern Sicily at 2,100 m water depth, records a variety of signals for geophysical and environmental long-term monitoring, including non-earthquake seismic signals that provide insights into the area’s geohazards. The signals analyzed for this paper are: (1) seismic signals associated with submarine landslides, (2) volcanic tremor, and (3) short duration events (SDEs). These seismic signals are analyzed together with pressure and hydrophone data to help identify their origins. Tectonic shifts can lead to submarine landslides. Volcanic tremor is the result of sustained pressure fluctuations, probably related to stress variations induced by magma movement. Increased tremor amplitudes recorded at NEMO-SN1 during lava fountain episodes from February to April 2013 suggest the presence of an east-southeast offshore location of the roots of Mt. Etna’s magma feeding system. SDEs are thought to result from hydrofracturing of carbonate outcroppings at the base of the Malta Escarpment that is possibly induced by changes in the stress field associated with magma movement.