HR: 1340h
AN: S53B-0211    [Abstracts]
TI: Bridging Long-period and Hand-picked Arrival Times of Teleseismic Body Waves
AU: * Oki, S
EM: toko@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute, Univ. of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, Tokyo, 113-0032 Japan
AU: Masters, G
EM: gmasters@ucsd.edu
AF: IGPP/University of California, San Diego, 8800 Biological Grade, La Jolla, CA 92037 United States
AU: Fukao, Y
EM: fukao@jamstec.go.jp
AF: IFREE/Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka, 237-0061 Japan
AU: Reif, C
EM: creif@ucsd.edu
AF: IGPP/University of California, San Diego, 8800 Biological Grade, La Jolla, CA 92037 United States
AB: It is well known that the S travel times of long-period Earth models delay several seconds to those of standard travel time tables. This discrepancy can be largely removed by taking the physical dispersion into consideration, where the reference frequency of standard travel time tables or short-period Earth models has been conventionally taken to be 1 Hz. Oki et. al. [2004] measured S-P travel times on the unfiltered broadband seismograms by cross-correlating the observed S waveform with those synthesized from the observed P waveform. The measured S-P times were added to the hand-picked P times to obtain the broadband S times, some of which were able to compare to the hand-picked S times. A reference frequency of 2 Hz was required to make the broadband and hand-picked S times consistent with each other. On the other hand, Bolton and Masters [2001] measured P and S travel times by cross-correlating the observed low-pass filtered P and S waveforms with those synthesized for a reference Earth model. The reference frequency was set at 0.5 Hz. We compared these two datasets in different frequency ranges to see their mutual consistency. In the two datasets there existed discrepancies of about 2, 4 and 2 sec for P, S and S-P times, respectively. After a correction for finite source duration for the long-period data, the P arrival times became consistent between the two datasets. There still remained 2 sec of discrepancy for S and S-P times. Assuming that this discrepancy represents the effect of physical dispersion, we searched for the reference frequency that can remove the 2-sec offset. This search yielded a value of 2 Hz in agreement with the result of Oki et. al [2004]. The reference frequency of 2 Hz can bridge consistently long-period, broadband and hand-picked S arrival times, and hence can be regarded as the characteristic frequency defining the onset of teleseismic body waves.
DE: 7260 Theory and modeling
DE: 7294 Instruments and techniques
DE: 5144 Wave attenuation
DE: 7203 Body wave propagation
DE: 3909 Elasticity and anelasticity
SC: Seismology [S]
MN: 2004 AGU Fall Meeting