GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.3 GNGTS 2023 On seismic ambient noise cross-correlation and surface-wave attenuation L. Boschi, F. Magrini, F. Cammarano Mapping variations in the attenuation of seismic energy is important for understanding dissipative mechanisms in the lithosphere, and for modeling ground shaking associated with earthquakes. We discuss the theoretical relationship between the cross correlation of ambient Rayleigh waves (seismic ambient noise) and the attenuation parameter α associated with Rayleigh-wave propagation. We formulate the related inverse problem, to determine α from recorded ambient signal. We generate synthetic recordings of numerically simulated ambient seismic noise in several experimental setups, characterized by different source distributions and different values of attenuation coefficient, and use them to verify that our method can accurately identify true attenuation. We apply the so validated method to the data from the EarthScope Transportable Array (USArray) in the 3–15 s period range. We interpret the resulting, frequency-dependent Rayleigh-wave attenuation maps, and corresponding phase-velocity maps, in terms of three-dimensional structure of North American crust.