부산대학교 도서관

We have provided the first estimate of scattering and intrinsic attenuation for the Gargano Promontory (Southern Italy) analyzing 190 local earthquakes with ML ranging from 1.0 to 2.8. To separate the intrinsic QiQsQβQcQβQcTstart=1.5TSTLQcQiQcQsQiQiQcQcQi and scattering QiQsQβQcQβQcTstart=1.5TSTLQcQiQcQsQiQiQcQcQi quality factors with the Wennerberg approach (1993), we have measured the direct S waves and coda quality factors (QiQsQβQcQβQcTstart=1.5TSTLQcQiQcQsQiQiQcQcQi, QiQsQβQcQβQcTstart=1.5TSTLQcQiQcQsQiQiQcQcQi) in the same volume of crust. QiQsQβQcQβQcTstart=1.5TSTLQcQiQcQsQiQiQcQcQi parameter is derived with the coda normalization method (Aki 1980) and QiQsQβQcQβQcTstart=1.5TSTLQcQiQcQsQiQiQcQcQi factor is derived with the coda envelope decay method (Sato 1977). We selected the coda envelope by performing an automatic picking procedure from QiQsQβQcQβQcTstart=1.5TSTLQcQiQcQsQiQiQcQcQi up to 30 s after origin time (lapse time QiQsQβQcQβQcTstart=1.5TSTLQcQiQcQsQiQiQcQcQi). All the obtained quality factors clearly increase with frequency. The QiQsQβQcQβQcTstart=1.5TSTLQcQiQcQsQiQiQcQcQi values correspond to those recently obtained for the area. The estimated QiQsQβQcQβQcTstart=1.5TSTLQcQiQcQsQiQiQcQcQi are comparable to the QiQsQβQcQβQcTstart=1.5TSTLQcQiQcQsQiQiQcQcQi at all frequencies and range between 100 and 1000. The QiQsQβQcQβQcTstart=1.5TSTLQcQiQcQsQiQiQcQcQi parameter shows higher values than QiQsQβQcQβQcTstart=1.5TSTLQcQiQcQsQiQiQcQcQi, except for 8 Hz, where the two estimates are closer. This implies a predominance of intrinsic attenuation over the scattering attenuation. Furthermore, the similarity between QiQsQβQcQβQcTstart=1.5TSTLQcQiQcQsQiQiQcQcQi and QiQsQβQcQβQcTstart=1.5TSTLQcQiQcQsQiQiQcQcQi allows us to interpret the high QiQsQβQcQβQcTstart=1.5TSTLQcQiQcQsQiQiQcQcQi anomaly previously found in the northern Gargano Promontory up to a depth of 24 km, as a volume of crust characterized by very low seismic dumping produced by conversion of seismic energy into heat. Moreover, most of the earthquake foci fall in high QiQsQβQcQβQcTstart=1.5TSTLQcQiQcQsQiQiQcQcQi areas, indicating lower level of anelastic dumping and a brittle behavior of rocks.