Abstract
In the present study, we investigated the dispersion characteristics of medium-to-long period Rayleigh waves (2 s < T < 20 s) using both singlestation techniques (multiple-filter analysis, and phase-match filter) and multichannel techniques (horizontal slowness [p] and angular frequency [~] stack, and cross-correlation) to determine the velocity structure for the Mt. Etna volcano. We applied these techniques to a dataset of teleseisms, as regional and local earthquakes recorded by two broad-band seismic arrays installed at Mt. Etna in 2002 and 2005, during two seismic surveys organized by the Istituto Nazionale di Geofisica e Vulcanologia (INGV), sezione di Napoli. The dispersion curves obtained showed phase velocities ranging from 1.5 km/s to 4.0 km/s in the frequency band 0.05 Hz to 0.45 Hz. We inverted the average phase velocity dispersion curves using a non-linear approach, to obtain a set of shear-wave velocity models with maximum resolution depths of 25 km to 30 km. Moreover, the presence of lateral velocity contrasts was checked by dividing the whole array into seven triangular sub-arrays and inverting the dispersion curves relative to each triangle.
Highlights
High-resolution seismic images of crustal layers are extremely important for the retrieving of physical and mechanical properties of the materials
The inversion of Rayleigh-wave dispersion curves obtained with different techniques has provided very robust S-wave (Vs) velocity models for the summit area of Mt
Etna volcano, which are compatible with recent models derived from seismic tomography
Summary
High-resolution seismic images of crustal layers are extremely important for the retrieving of physical and mechanical properties of the materials. We have used mid-period and long-period Rayleigh waves from teleseismic (D [epicentral distance in angular degrees] > 13 ̊), regional (1 ̊< D < 13 ̊), and local (D < 1 ̊) earthquakes recorded by broad-band temporary arrays to determine the phase-velocity dispersion of Rayleigh waves in the frequency range from 0.05 Hz to 0.45 Hz. The inversion of the retrieved dispersion curves provides shear-wave velocity profiles down. The second survey lasted four months (from July to October, inclusive, 2005) and consisted of the installation of five Lennartz M24 stations equipped with Lennartz LE-3D/20s threecomponent broad-band seismometers, with a flat amplitude response curve from 0.05-50 Hz (Figure 1) Both of these seismic arrays were deployed and operated by the Istituto Nazionale di Geofisica e Vulcanologia, sezione di Napoli, using their mobile seismic network equipment. We selected events with good signal-to-noise ratios (over a threshold of 10), measured in terms of the RMS of the signal
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