Broadband strong-motion observation for aftershocks of the 1997 northwestern Kagoshima earthquakes

Y. Fujii, H. Futamure, H. Takenaka, T. Matsushima, K. Umakoshi, K. Tashiro, S. Suzuki

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Abstract

An earthquake with MJMA 6.5 occurred at the northwest region of Kagoshima prefecture on March 26, 1997. We started observing the aftershocks at KKN (31.9794°N 130.4442°E) on March 28, 1997 using the broadband strong-motion seismometer (VSE 11 C/12 C). The observation was finished on September 30, 1997. Also another VSE 11 C/12 C was installed at the station SIBI (31.9677°N 130.3524°E). After all, we observed 100 events at KKN, including the second large earthquake (MJMA 6.2) on May 13. The purpose of this paper is to describe the detail of observational conditions, and to report the result of the preliminary analysis of the observed seismograms. We transformed the horizontal components of seismograms observed at SIBI into the radial and transverse components, and analyzed the Fourier amplitude spectra for S-wave parts of the aftershocks observed at KKN have a sharp peek at the frequency of 4.0-6.0 Hz, which is not seen for the seismograms observed at SIBI. Also, we integrated the velocity seismograms to get the displacement waveforms. The observation in short epicentral distances made it possible to recognize the near-field term in all of the displacement waveforms.

Original languageEnglish
Pages (from-to)25-46
Number of pages22
JournalScience Reports of the Kyushu University, Department of Earth and Planetary Sciences
Volume20
Issue number1
Publication statusPublished - Jan 1 1998

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seismograms
strong motion
seismogram
aftershock
earthquakes
broadband
earthquake
waveforms
seismographs
seismograph
S waves
S-wave
near fields
stations

All Science Journal Classification (ASJC) codes

  • Space and Planetary Science
  • Earth and Planetary Sciences(all)

Cite this

Broadband strong-motion observation for aftershocks of the 1997 northwestern Kagoshima earthquakes. / Fujii, Y.; Futamure, H.; Takenaka, H.; Matsushima, T.; Umakoshi, K.; Tashiro, K.; Suzuki, S.

In: Science Reports of the Kyushu University, Department of Earth and Planetary Sciences, Vol. 20, No. 1, 01.01.1998, p. 25-46.

Research output: Contribution to journalArticle

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AU - Tashiro, K.

AU - Suzuki, S.

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