Intrinsic Qp at Mt. Etna from the inversion of rise times of 2002 microearthquake sequence

S. de Lorenzo, M. Filippucci, E. Giampiccolo, D. Patanè


About three-hundred microearthquakes, preceeding and accompanying the 2002-2003 Mt. Etna flank eruption,
were considered in this study. On the high-quality velocity seismograms, measurements of the first half cycle of
the wave, the so-called rise time ?, were carried out. By using the rise time method, these data were inverted to
infer an estimate of the intrinsic quality factor Qp of P waves and of the source rise time ?0 of the events, which
represents an estimate of the duration of the rupture process. Two kind of inversions were carried out. In the first
inversion ?0 was derived from the magnitude duration of the events, assuming a constant stress drop and Qp was
inferred from the inversion of reduced rise times ???0. In the second inversion both ?0 and Qp were inferred from
the inversion of rise times. To determine the model parameters that realize the compromise between model simplicity
and quality of the fit, the corrected Akaike information criterion was used. After this analysis we obtained
Qp=57±42. The correlation among the inferred ?0 and Qp, which is caused by some events which concomitantly
have high ?0 (>30 ms) and high Qp (>100) indicates that the technique used is able to model rise time versus
travel time trend only for source dimensions less than about 80 m.


intrinsic quality factor;stress drop;rise time;corrected Akaike information criterion

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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X