HR: 08:45h
AN: T31D-04    [Abstracts]
TI: Effects of 3D Velocity and Attenuation in the Tonga-Fiji Subduction Zone
AU: * Savage, B
EM: savage13@dtm.ciw.edu
AF: Department of Terrestrial Magnetism, Carnegie Institute of Washington, 5241 Broad Branch Rd, NW, Washington, DC 20015 United States
AU: Wiens, D A
EM: doug@kermadec.wustl.edu
AF: Department of Earth and Planetary Sciences Washington University, 1 Brookings Drive, St. Louis, MO 63130 United States
AU: Tromp, J
EM: jtromp@gps.caltech.edu
AF: Seismological Laboratory, California Institute of Technology, 1200 E California Blvd MSC 252-21, Pasadena, CA 91125 United States
AB: The current understanding of a subduction zone's temperature and composition is limited. Much of our recent knowledge of subduction zones comes from earthquake locations, geochemical measurements, and lab based experiments. Recently, two studies of the Tonga-Fiji subduction zone have presented tomographic images of velocity and attenuation (Roth et al., 1999; Zhao et al., 1997). Roth et al. (2000) then combined these two tomographic models of the Tonga-Fiji subduction zone to derive an empirical relationship between changes in velocity and attenuation. This relationship agrees well with two independent, experimental data sets (Jackson et al., 1992; Sato et al., 1989). Using the tomographic velocity model and the empirical relationship between velocity and attenuation we create synthetic seismograms for the Tonga-Fiji subduction zone to test whether a simple increase in velocity accurately depicts this subduction zone. To construct the model we use the tomographic model of Zhao et al. (1997) to create a shear velocity model using a simple Vs/Vp ratio. Following Roth et al. (2000) these tomographic models are combined with the empirical relation between velocity and attenuation to create an attenuation model. The resulting synthetics are compared to recorded data to validate the tomographic velocity model and the empirical relation between velocity and attenuation. Any mismatch in this comparison will provide a basis for further refinement of the tomographic models and the velocity-attenuation relation. The synthetics are created using the SPECFEM3D global code (Komatitsch et al., 2002) with the new addition of a three-dimensional attenuation operator. Attenuation is simulated by a set of standard linear solids over the desired frequency range as described in Liu et al. (1976). Our initial results at a minimum period of 3.3 seconds suggest that the attenuation structure plays a minor role for the present source-receiver geometry. The addition of the 3D attenuation structure does distort the recording significantly in amplitude and phase.
DE: 7203 Body waves
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 7290 Computational seismology
DE: 8123 Dynamics: seismotectonics
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Tectonophysics [T]
MN: Fall Meeting 2005