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Detailed Reference Information |
Castro, R.R., Trojani, L., Monachesi, G., Mucciarelli, M. and Cattaneo, M. (2000). The spectral decay parameter ¿ in the region of Umbria-Marche, Italy. Journal of Geophysical Research 105: doi: 10.1029/2000JB900236. issn: 0148-0227. |
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We analyze 44 earthquakes (M2.1--4.1) recorded by the Marchesan Seismograph Network during the 1997 Umbria-Marche sequence. We calculated the spectral decay parameter &kgr; <Anderson and Hough, 1984> using 33 events (M2.2--4.1) and fc<10 Hz located in the middle of the rupture area. Although the source-station paths have approximately the same distance (¿2.5 km) and azimuth for a given site, the estimates of &kgr; show great variability at all the stations. Even events with small standard deviation on the estimate of &kgr; can have a value 2--3 times different from that estimated for other events located within the 2.5 km. This observation suggests that the attenuation near the source can change significantly in a small distance range. We separated source and path effects by performing a generalized spectral inversion. We dismissed events with source functions having corner frequencies between 10 and 20 Hz, the frequency band where &kgr; was estimated. With the best estimates of &kgr; we calculated the mean for each site, and we observed an apparent azimuthal variation of the attenuation. We used the observed changes of &kgr; to estimate the near-source attenuation, finding that in a distance of 2 km, Q may vary between 16 and 52, depending on the source-station direction. The results of the analysis suggest that the most likely cause of the observed variability of &kgr; is the spatial variation of Q near the seismogenic zone. ¿ 2000 American Geophysical Union |
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Abstract |
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Keywords
Seismology, Seismology, Continental crust, Seismology, Earthquake ground motions and engineering, Seismology, Earthquake parameters |
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Publisher
American Geophysical Union 2000 Florida Avenue N.W. Washington, D.C. 20009-1277 USA 1-202-462-6900 1-202-328-0566 service@agu.org |
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