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.