科研之友
微信
新浪微博
Facebook
分享链接
摘要
The observable decay with frequency (f) of Fourier amplitude spectra for ground-motion recordings is controlled by a parameter kappa: exp (-pi kappa f). We analyze data from the KiK-net network, which is composed of stations with paired ground-motion sensors, one at the surface and one in a borehole. This study estimates kappa for all KiK-net stations, using earthquakes recorded between 1998 and 2006. An inversion scheme is used to separate site, source, and path contributions to kappa. We correlate the site component of kappa (kappa(0)), estimated at the surface and the depth, with different S-wave velocity measures and with the fundamental resonant frequency of the site. The results show that the best correlations involve shallow soil S-wave velocity measures. The superficial layers of the soil predominantly influence kappa(0), but a remaining component with a deep origin is also observed. The source component of kappa is small and presents a clear regional dependence, while no correlations with magnitude or depth of the earthquake are observed. Data from the Next Generation of Attenuation (NGA) database are also used to estimate kappa(0) (surface site component) at the stations with a measured V(S30) value. The V(S30)-kappa couples estimated from both KiK-net and NGA data are compared with results from the literature, and a new correlation is established. Most of the ground-motion prediction equations (GMPEs) for stable continental regions are derived for very hard rock sites (V(S30) > 2000 m/s). In order to use these equations for standard rock sites (V(S30) around 800 m/s), conversion factors are required. Using the new correlation V(S30)-kappa and the host-to-target adjustment method of Campbell (2003), we compute amplification factors from very hard rock to rock sites. We show that in these conversions, the effects of both V(S30) and kappa have to be taken into account.
- 出版日期2011-12
