HR: 0800h
AN: S41C-1028    [Abstracts]
TI: Constraints on Inner Core Rotation Rate From Improved Inner Core Wavespeed Gradients
AU: * DeRosier, S
EM: sderosie@u.washington.edu
AF: University of Washington, Box 351310, Seattle, WA 98195 United States
AU: Creager, K C
EM: kcc@ess.washington.edu
AF: University of Washington, Box 351310, Seattle, WA 98195 United States
AB: A recent analysis of waveform doublets provides compelling evidence in support of differential rotation of the inner core relative to the mantle (Zhang et al., Science, 2005). Several pairs of South Sandwich Islands earthquakes, separated in time by up to 35 years, are sufficiently close to each other to produce PKP-BC and PKP-AB waveforms that are nearly identical. In addition, the Zhang et al. doublet study circumvents problems with earthquake locations inherent to previous studies. Despite this support for differential rotation, determining the rate and direction of rotation requires further knowledge of wavespeed gradients through the inner core. In an effort to further constrain the parameters of inner core rotation, we have collected seismograms from an array of 43 earthquakes near the South Sandwich Islands recorded at an array of about a hundred stations in the Alaska Seismic Network. We have also developed a multi-channel cross-correlation method to align the seismograms on the either the PKP-AB or the PKP-BC phases. We can then simultaneously invert travel times for the integrated effects of heterogeneity along ray paths in the inner core as well as small-scale structure near the base of the mantle, both on the source and receiver sides. By combining our estimate of inner core wavespeed gradients with data from seismic doublets, we should be able to tightly constrain the rate and direction of inner core rotation.
DE: 7207 Core (1212, 1213, 8124)
SC: Seismology [S]
MN: Fall Meeting 2005