Assessing seismic response of soft soil sites in hong kong using icrotremor records

Wong Yuk-Iung, John X. Zhao, Eddie Siu shu lam, Chau Kam-tim

Research output: Journal article publicationJournal articleAcademic researchpeer-review

13 Citations (Scopus)


Microtremor records have been used to assess seismic ampiification of sou sites in Hong Kong. The method is based on ratios of horizontal and vertical camponents of microtremor (ambient noise) recards, and the ratios are aften referred to as Nakamura’s ratios. The peakfrequency of the Nakamura’s ratio carrelates well with thefundamental modal frequency estimated from the site shear wave velocities which were derived by a vertical seismic profiling method or were converted from SPT data. The amplitudes of the ratios are very stable and the standard deviation of the ratios derived from a series of measurements is reasonably small. Results from rock sites show that the ratios take a value of unity at a wide frequency range when the site has no large topographical effect. The ratios are generally larger than unity if the site has topographical effect but no dominant peak appears in the ratios. Results from sou sites show that a dominant peak appears at the fundamental frequency of the site and the amplitudes of the dominant peak are between 6 and 12 for mean ratios. It is plausible to take the maximum value of the ratios as the peak amplification of the sou layers (Faurler spectral ratla) at small strain motions. Results from soli sites also show that many sites on reclaimed land and land fills are likely to be susceptible to seismic amplification. The seismic ampliflcation has possible implicatians for those buildings with about 20 storeys or less founded on soil sites. Site fundamental modal frequencies estimated by microtremor records have been obtained fram extremely small strain motions and they are likely to change during a moderate or strong earthquake shaking. However, overseas experience has shown that this method can be used to identify soil sites susceptible to seismic amplification.
Original languageEnglish
Pages (from-to)70-79
Number of pages10
JournalHKIE Transactions Hong Kong Institution of Engineers
Issue number3
Publication statusPublished - 1 Jan 1998


  • Hong Kong
  • Microtremor Recards
  • Nakamura’s Ratio measurements is reasonably small
  • Seismic Response
  • Soft Sail

ASJC Scopus subject areas

  • General Engineering


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