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  • Article
  • Open Access

Calibration of amplification factors using KiK-net strong-motion records: toward site effective estimation of seismic intensities

Earth, Planets and Space200759:BF03352054

  • Received: 16 April 2007
  • Accepted: 10 September 2007
  • Published:


Estimated seismic intensities using conventional relationships are not always in agreement with those observed at specific sites. We investigate subsurface amplification factors using the KiK-net strong-motion data recorded both in the borehole and on the ground surface and attempt to estimate more accurate intensities at a given site. Here the amplification factors are evaluated using the ratios of peak velocity amplitudes Vsurf/Vbor that are calculated from records on the ground surface and in the borehole. The ratios (amplification factors) decrease with hypocentral distance in general, but the attenuation characteristics vary from station to station. At stations where large amplifications are observed, the ratios show large scatter relative to the empirical amplification formulas. The variation is also affected by the incident direction of seismic waves as well as the hypocentral distance. We derived empirical amplification formulas of Vsurf/Vbed where Vbed is the peak velocity on the engineering bedrock as a function of hypocentral distance at individual stations (i.e. specific sites) in place of the conventionally used amplification constants. The estimated intensities using the site-effective formulas show substantial improvement at most of the stations in comparison with those calculated using conventional formulas.

Key words

  • KiK-net
  • local site effect
  • attenuation relationship
  • seismic intensity