HR: 1330h
AN: S22B-0441    [PDF]
TI: The Reference Frequency of Teleseismic Body Waves
AU: * Oki, S
EM: toko@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku,, Tokyo, 113-0032 Japan
AU: Fukao, Y
EM: fukao@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku,, Tokyo, 113-0032 Japan
AU: Fukao, Y
EM: fukao@eri.u-tokyo.ac.jp
AF: Institute for Fronteier Research on Earth Evolution, Japan Marine Science and Technology Center, 2-15 Natsushima-cho, Yokosuka-shi, Kanagawa, 237-0061 Japan
AU: Obayashi, M
EM: obayashi@jamstec.go.jp
AF: Institute for Fronteier Research on Earth Evolution, Japan Marine Science and Technology Center, 2-15 Natsushima-cho, Yokosuka-shi, Kanagawa, 237-0061 Japan
AB: Anelasticity of the Earth causes physical dispersion of seismic waves. Our question is addressed to how to choose the reference frequency of physical dispersion, $f_0$, consistent with the extensive data sets of hand-picked body wave arrival times compiled through the long history of seismology. The appropriate choice of reference frequency is also important to determine arrival times of body waves, especially later arrival times, from broadband seismograms by fitting observed to synthetic waveforms. Setting the reference frequency to be the conventional one, 1 Hz, we measured $S$-$P$ differential travel times by waveform fitting. We found a systematic discrepancy between the measured and hand-picked $S$-$P$ times that can be removed by changing $f_0$ from 1 Hz to 2 Hz. This change of $f_0$ requires a correction in $Q$ of the \textit{PREM} model: 1) if $Q$ is strictly frequency-independent, we need a 15 % increase in $Q$ value, or 2) if $Q$ is fixed to the value given by \textit{PREM} at a period of 200 s, we need to introduce a small frequency-dependence in $Q$, where the dependence is expressed by the power law with an exponent of 0.04.
DE: 3909 Elasticity and anelasticity
DE: 5144 Wave attenuation
DE: 7203 Body wave propagation
DE: 7207 Core and mantle
SC: Seismology [S]
MN: 2003 Fall Meeting