Volcanic Tremor of Mt. Etna (Italy) Recorded by NEMO-SN1 Seafloor Observatory: A New Perspective on Volcanic Eruptions Monitoring

Volcanic Tremor of Mt. Etna (Italy) Recorded by NEMO-SN1 Seafloor Observatory: A New Perspective on Volcanic Eruptions Monitoring

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The NEMO-SN1 seafloor observatory, located 2100 m below sea level and about 40 km from Mt.Etna volcano, normally records a background seismic signal called oceanographic noise.This signal is characterized by high amplitude increases, lasting up to a few days, and by two typical 0.

1 and 0.3 Hz frequencies in its spectrum.Particle motion analysis shows a strong E-W directivity, coinciding with the direction of sea waves; gravity waves induced by local winds are considered the main source of oceanographic noise.

During the deployment of NEMO-SN1, the vigorous 2002–2003 Mt.Etna eruption occurred.High-amplitude background signals were recorded eeboo coupons during the explosive episodes accompanying the eruption.

The spectral content of this signal ranges from 0.1 to 4 Hz, with the most powerful signal in the 0.5–2 Hz band, typical of an Etna volcanic tremor.

The tremor recorded by NEMO-SN1 shows a strong NW-SE directivity towards the volcano.Since the receiver is underwater, we inferred the presence of a circulation of magmatic fluids extended under the seafloor.This process is able to generate a signal strong enough to be recorded here by the NEMO-SN1 seafloor observatory that hides frequencies linked to the oceanographic noise, permitting the offshore monitoring of the volcanic activity of Mt.

Etna.