Volcanic Tremor of Mt. Etna (Italy) Recorded by NEMO-SN1 Seafloor Observatory: A New Perspective on Volcanic Eruptions Monitoring
Abstract
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 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 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.
- Publication:
-
Geosciences
- Pub Date:
- March 2019
- DOI:
- 10.3390/geosciences9030115
- Bibcode:
- 2019Geosc...9..115S
- Keywords:
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- Mt. Etna volcano;
- oceanographic noise;
- volcanic tremor;
- volcanic monitoring by seafloor observatories