HR: 0800h
AN: DI31A-0264    [Abstracts]
TI: Simulations of Inner Core Coda Waves with a Multiple-Scattering Phonon Based Algorithm
AU: * Koper, K
EM: koper@eas.slu.edu
AF: Department of Earth and Atmospheric Sciences, Saint Louis University, St. Louis, MO 63108, United States
AU: Shearer, P
EM: pshearer@ucsd.edu
AF: Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, La Jolla, CA 92093, United States
AU: Peng, Z
EM: zpeng.seismo@gmail.com
AF: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332, United States
AU: Vidale, J
EM: john_vidale@mac.com
AF: Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, United States
AB: Emergent, low-slowness coda waves following precritical PKiKP phases have now been observed at a geographically and geometrically diverse set of seismic arrays. Forward simulations using ray-theoretical single scattering theories have shown that it is difficult to match the observed properties with heterogeneity in the mantle, along the core-mantle boundary, or along the inner core boundary; only by placing heterogeneity within the volume of the inner core can the observations be well-matched. In this study, we present new simulations of PKiKP coda waves using a more complete, phonon-based approach that allows for multiple scattering between source and receiver. We experimented with a wide range of scattering models and again found that only by distributing heterogeneities within the volume of the inner core can the observations be fit. The thickness of the scattering layer must be at least 200-300~km and the data do not rule out the existence of heterogeneities throughout the inner core. There is a strong trade-off among the model parameters, and high-quality models can be found with correlation lengths of 1-16~km and velocity perturbations of 0.8%-10%. Perturbations in density are not required to fit the data. There is also a smaller trade-off with the value of Q_p in the inner core. High Q_p values require weaker models of inner core scattering to provide equivalent fits to the observations. Our preferred model has a correlation length of 1~km, an rms velocity perturbation of 0.8%, and an inner core Q_p of 360.
DE: 7203 Body waves
DE: 7207 Core (1212, 1213, 8124)
DE: 8124 Earth's interior: composition and state (1212, 7207, 7208, 8105)
SC: Study of the Earth's Deep Interior [DI]
MN: 2007 Fall Meeting