HR: 14:55h
AN: S53D-05    [Abstracts]
TI: Temporal distribution of strong high frequency energy radiation inferred from far-field broadband records
AU: * Hara, T
EM: thara@kenken.go.jp
AF: IISEE, BRI, 1 Tatehara, Tsukuba, 305-0802, Japan
AB: Recently, we developed a new method to determine earthquake magnitudes using durations of high frequency energy radiation and the maximum displacement amplitudes measured from processing of first arriving P-waves (Hara, 2007a. Earth Planets Space, 59, 227-231; Hara, 2007b. Earth Planets Space, 59, 561-565). In this technique, the difference between P arrival time and the time when the amplitude of high bandpass (2-4 Hz) filtered seismogram becomes the largest is used to set width of moving window for smoothing time series. In this study, we measured these differences for large shallow earthquakes that occurred between 1995-2007. We normalized them by centroid time shifts to find the low frequency in the range of 0-20 % and the high frequency around 50 %. This result supports the effectiveness of the measurement procedure of duration of the high frequency energy radiation of Hara (2007a, b). We also applied our measurement procedure to the January 15, 1993 Kushiro-Oki, July 12, 1993 Hokkaido-Nansei-Oki, and December 28, 1994 far east off Sanriku earthquakes. We compared the measured time differences to the results of inversion of strong motion records to find the qualitative agreement between them.
DE: 3270 Time series analysis (1872, 4277, 4475)
DE: 7203 Body waves
SC: Seismology [S]
MN: 2007 Fall Meeting