Observation by Means of An Underground Ring Laser Gyroscope of Love Waves Generated in the Mediterranean Sea: Source Direction and Comparison with Models

Abstract

In fall 2018, we have observed, by means of an underground ring laser gyroscope, the microseismic (MS) activity induced by the Mediterranean Sea in the 2–5 s period range. In the amplitude spectra, a clear peak highly correlated with a collocated seismometer appears during a large storm activity ranging from 24 November to 1 December 2018. The peak of the spectra, both for rotation rate and acceleration, are located at 3.3 s. The peak amplitudes are of 8×10−10 rad/s−1 and 3×10−6 ms−2, respectively, for vertical rotation rate and horizontal acceleration. We perform the source direction estimation by maximizing the correlation of the vertical rotation rate with the transverse acceleration. The local estimation of the direction of the wavefield is then compared with the sea state hindcasts that provide a modeling of the possible MS noise sources.

Monitoring Local Earthquakes in Central Italy Using 4C Single Station Data

“…We report as an example the result of two events in Figure 2 . In both the sub-figures of Figure 2 , we can note a high correlation portion before the p onset that is due to the Love waves present in the secondary microseism generated by the Mediterranean Sea that is better described in [ 10 ].…”

“…We report as an example the result of two events in Figure 2. In both the sub-figures of Figure 2, we can note a high correlation portion before the p onset that is due to the Love waves present in the secondary microseism generated by the Mediterranean Sea that is better described in [10]. The resolution of BAZ with a single seismometer relies on analyzing the projections of the P onset over the radial and vertical axes which is not always clear, leaving us then with an ambiguity.…”

“…This ensemble of instruments constitutes a four-component (4C) seismic station, and they are available on EIDA under the station name GIGS of the INGV network [7]. The Gingerino instrument right after his commissioning permitted several seismological studies from distant earthquakes [8,9] to storm generated noise [10] and finally local earthquakes in [11] i.e., the topic of this paper. The theory underneath rotations in seismology is largely explored in literature [12,13] and new processing studies are available [14,15] as well as new instruments [16].…”

Cyclone Signatures in the South-West Indian Ocean from Two Decades of Microseismic Noise

“…Our polarization analyses show that a cyclone located in the Mozambique Channel (e.g., Idai, March 2019, Figure S5c) does not influence the recorded SM in La Réunion, which is fully consistent with the PSD results in Section 3.1.3 that showed weak amplitudes. Tracking the cyclone trajectory is beyond the scope of the present work, but should be achieved using different methods e.g., [9,[18][19][20][21].…”

“…Gualtieri et al [17] analyzed 22 years of seismic data to estimate the relationship between the TC in the Pacific Ocean and the SM recorded by seismic stations located in the northwest of Pacific. Several studies involving the use of the microseismic data have shown the feasibility of tracking the TC using the microseismic noise e.g., [9,16,[18][19][20][21]. Apart from the works of Davy et al [4,9] and Barruol et al [13], none of these studies focused on the cyclone activity in the SWIO.…”