Abstract

We computed the source parameters of 135 local earthquakes that occurred in southeastern Sicily (Italy) between 1994 and 2001. Magnitudes ranged from 0.6 to 2.5. The source parameters were determined from the spectral analysis of P waves, after corrections for attenuation and site effects. P-wave quality (Qp) and site (S) factors are known in the two frequency ranges 3–9 Hz and 16–27 Hz (Giampiccolo et al., 2003). Because the correction for Qp and S over the whole spectrum could not be performed, a new approach to estimate spectral parameters was applied. We defined the new notion of “holed spectrum” to specify a spectrum lacking corrected spectral amplitude values within a certain frequency range, whereas we referred to a “whole spectrum” to specify when the entire analyzed frequency band was used. A detailed statistical analysis showed that dealing with the holed spectrum did not lead to significant differences in the estimate of spectral parameters. Displacement holed spectra, corrected by the attenuation and site response, were then used to estimate source parameters. Seismic moments ranged from 1017 to 1020 dyne cm, and source dimensions from 150 to 500 m. In general, the stress-drop values obtained analyzing P-wave spectra were very low, because they mainly span the range of 0.05–5 bars.

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