Application of H/V Method in a Small-Scale Basin

Abstract eng:
Nakamura method, i.e. H/V method of ambient tremor, is applied in a small-scaled lacustrine sedimentary basin in Northeast China, which is suspected to be a meteorite impact crater covered by soft and deep lacustrine deposit layers. The ambient tremor was observed for hours at 50 points in the basin, and then horizontal Fourier amplitudes to vertical Fourier amplitudes ratios, i.e. H/V spectral ratios, were calculated. The results showed that in the whole basin the predominant periods of H/V spectral ratios of all observation points were identical, but with different amplitudes. The in situ geological drillings showed that the peak values of H/V spectral ratio amplitudes at the predominant period (corresponding to 0.72Hz) depended on the depths of soft deposit soil and the distances to the basin center. The fact that H/V spectral ratios on the ground surface in the whole basin had only one predominant period but with different amplitudes indicated that the ambient tremor propagating through the deep and soft soil layers was affected by the three dimensional structure of lacustrine sediments, rather than the local soil depth right under the observation point . Our observations in several other sites showed that the H/V spectral ratios were not sufficient reliable when there were strong vibration sources on the ground surface nearby, meanwhile the H/V spectral ratios in this basin gave a satisfied result. We thought that no obvious vibration sources in this basin guaranteed the reliability of Nakamura method. In addition, amplitudes of H/V spectral ratios at the predominant period should be used in soil velocity inversion when the soil layers vary violently in horizontal plan, which could not be treated as one dimension layered medium any more.

• Export as: BibTeX | MARC | MARCXML | DC | EndNote | NLM | RefWorks
• Add to your basket