Abstract
Estimating possible site effect is an integral part of evaluation of the seismic hazard and reduction of earthquake damages. In regions with low or moderate seismicity as in Israel, the site response should be determined by analytical tools. These computations require knowledge of the subsurface geological structure in terms of shear-wave velocity (Vs) profile down to seismic bedrock. Conventionally, this problem is resolved by joint implementation of Horizontal-to-Vertical Spectral Ratios (HVSR or Nakamura’s) technique, which is based on ambient noise measurements and seismic methods such as S-wave refraction or Multichannel Analysis of Surface Waves (MASW) method. The first one does not allow deep penetration of seismic waves because of its weak source. The MASW method using 4.5 Hz geophones is restricted in penetration depth of surface waves because of frequency (wavelength) limitations. In this study, we have applied 2.5 Hz geophones and special data processing to provide constructing Vs section to a depth of 100 m and deeper. In combination with HVSR measurements, MASW enables constructing reliable subsurface model, which could be integrated into the seismic hazard assessment. Testing of this combined methodology was carried out at a number of sites with differing geological structures in Israel.
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