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The objective determination of the instantaneous predominant frequency of seismic signals and inferences onQ of coda waves |
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| Authors: | Antonio Rovelli Sandro Marcucci Giuliano Milana |
| Institution: | 1. Istituto Nazionale di Geofisica, Via di Villa Ricotti 42, 00161, Roma, Italy 2. ENEA-PAS, CRE-Casaccia, Via Anguillarese, 00100, Roma, Italy 3. ENEA-DISP, Via Vitaliano Brancati 48, 00144, Roma, Italy |
| Abstract: | A technique to detect spectrum variations versus time along seismic signals is applied to coda waves of local earthquakes (Friuli, Northern Italy). The technique consists of an autoregressive modeling and utilizes nonlinear spectral analysis where the spectrum of stochastic processes is estimated as the transfer function of the filter that whitens the process under analysis. This approach appears to be particularly well suited to those investigations where automatic measurements of the instantaneous frequency have to be carried out on digital data. The detection of variations of the instantaneous frequency along the coda allows computation of seismic-Q in the lithosphere and its frequency dependence: the result obtained is $$Q = 100f^{0.4} $$ which appears to be strongly consistent with that, based on the estimate of the coda amplitude decay in the band including the most significant frequencies of the signals under analysis. |
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