• Rotational seismology
• Love wave dispersion curves
• Back-azimuth estimation
• Time-Frequency analysis

The aim of this work is to compare earthquake-induced ground rotations observed at the GINGERino and G ring-laser gyroscopes, located at the Gran Sasso National Laboratories and Geodetic Fundamentalstation Wettzell, respectively, with the co-located translational measurements from standard seismometer. By computing the Power Spectral Density (PSD) of vertical rotation rate and transverse acceleration I firstly identify the signal to noise ratio (SNR) as a function of frequency, and then, by applying Time-Frequency Analysis, I individuate the most energetic frequency bands as a function of time for both the instruments for five teleseismic events. Then, rotation rate and acceleration are correlated in order to quantify similarities between the two signals. The first aim is the back-azimuth angle estimation (direction of the incoming wavefield), attained searching for the correct angle which gives the maximum value of the correlation coefficient between transverse acceleration and vertical rotation rate in a sliding time window. The second aim is the horizontal phase velocities estimation from the co-located measurements of rotation and translation, and the subsequent derivation of Love waves dispersion curves. This goal is attained by computing the zero-lag correlation coefficient (ZLCC) between translational and rotational traces, and estimating the phase velocity from a linear regression of the amplitudes of the two signals, for those time intervals over which the ZLCC is above a given threshold (Igel et al., 2005). Iterating the procedure over narrow band-pass filtered traces, it is possible to obtain a dispersion curve for the selected wave packet (Igel et al., 2007).
The estimated Love wave dispersion curves are then compared against the theoretical dispersion curve derived from the Preliminary Reference Earth Model (PREM) of Dziewonski and Anderson (1981).