HR: 0800h
AN: S41A-0245    [Abstracts]
TI: Low Intrinsic Attenuation and High Scattering Attenuation Near 1Hz in the Crust of the Tanzanian Craton
AU: * Jemberie, A L
EM: Alemayehu_Jemberie@arw.aon.com
AF: Aon Re Inc, 200 E randolph Street, Chicago, IL 60601,
AU: Nyblade, A A
EM: andy@geosc.psu.edu
AF: Department of Geoscices, Penn State, University Park, PA 16802,
AB: A 2-dimensional Energy Flux model method of Frankel and Wennerberg (1987) was used to obtain intrinsic and scattering attenuation models from regional and local earthquakes recorded by the 1994-1995 Tanzanian passive seismic experiment. Data for three earthquakes of magnitudes 5.9, 5.0 and 5.2, that occurred on 08/18/1994, 08/31/1994 and 11/12/1994, respectively, were obtained from IRIS. The E-W and N-S component data recorded by the array of stations were rotated to the great circle path to obtain transverse and radial components. The transverse component is chosen for two reasons (1) it is rich in coda, (2) and, most earthquake damage is from the SH component. Our results indicate low scattering Q (high scattering attenuation) and high intrinsic Q (low intrinsic attenuation) of the crust between an earthquake source and a station in the array. The high crustal intrinsic Q (QI) in the Crust may be explained by the absence of intrinsic attenuation mechanisms such as passage of fluids in interconnected cracks with in the crust. The absence of shallow very high temperature in the Tanzanian Craton may also contribute to the efficient passage of seismic wave energy in the crust. The low scattering Q (QS) may be explained by the presence of lateral heterogeneities, such as fractures, that redistribute energy from the main arrival phase into the coda by scattering mechanism.
DE: 7205 Continental crust (1219)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 7290 Computational seismology
SC: Seismology [S]
MN: 2007 Fall Meeting