HR: 0800h
AN: DI31A-0256    [Abstracts]
TI: Lateral Variations in the Scattering and Viscoelastic Properties of the Inner Core
AU: * Cormier, V F
EM: vernon.cormier@uconn.edu
AF: University of Connecticut, Physics Department, 2152 Hillside Road, Storrs, CT 06269- 3046, United States
AU: Stroujkova, A
EM: ana@westongeophysical.com
AF: Weston Geophysical Corp., 181 Bedford St., Suite 1, Lexington, MA 02420, United States
AB: Recent studies¹ find unusual high-frequency coda following the PKiKP phase, reflected from the inner core boundary in the area of the Central Pacific and observed at teleseismic distances between 50 ° to 90 ° range. The majority of the observations of such codas were made at short-period teleseismic arrays in the USA, Eastern Asia and Australia. An array analysis of the coda wavetrains shows the apparent horizontal velocity of the coda to be consistent with scattering from the uppermost inner core. The codas have different durations and frequency content depending on the PKiKP location of the ray incident point on the inner core boundary, as well as the distance between source and receiver. We examine the frequency dependence of the signals as a function of the event depth, magnitude, distance, and the location of the PKiKP incidence point. The observations show that the low frequency limit of the signal changes from 2 Hz in the east to 0.5-1 Hz in the west, possibly correlated with east-west changes observed in attenuation and pulse broadening of PKIKP in the 130 ° -150 ° range sampling the same regions of the inner core along equatorial paths.. Radiative transport modeling of PKiKP coda shapes in the 1-4 Hz band is combined with pseudospectral modeling of PKIKP pulses in the 0.2 to 1 Hz band to assess and separate the effects of scattering by small-scale heterogeneity from the effects of viscoelasticity in the uppermost inner core. Observed lateral variations in elastic attenuation and scattering in the uppermost inner core may record lateral variations in the solidification process of the inner core and lateral variations in fluid velocities of the outer core near the inner core boundary. ¹ Leyton, F., and K. Koper, J. Geophys. Res., 112, B05316, doi:10.1029/2006JB004369, 2007.
DE: 3285 Wave propagation (0689, 2487, 4275, 4455, 6934)
DE: 5144 Wave attenuation
DE: 7203 Body waves
DE: 7207 Core (1212, 1213, 8124)
DE: 7290 Computational seismology
SC: Study of the Earth's Deep Interior [DI]
MN: 2007 Fall Meeting