Preliminary site classification of free-field strong motion stations based on Wenchuan earthquake records

Abstract

During the great Wenchuan earthquake, about 460 permanent free-field stations in National Strong Motion Observation Network System (NSMONS) of China captured the main shock acceleration records. These records can be applied to site effect analyses, and then the site classification of those permanent stations can be carried out firstly, which will served as the fundamental information for further research. In this paper, the site of near-fault stations is classified by horizontal-to-vertical spectral ratio (HVSR) method according to the site class description of Japan earthquake resistant design code and response spectral shapes (RSS) method following the site class description of the 1997 Uniform Building Code (UBC) provisions. Then based on the detailed borehole data of those free-field stations, the equivalent shear wave velocity and overburden thickness are calculated and the site classifications are given by Chinese code for seismic design of buildings. Furthermore, for the stations having successful microtremor test data, the site dominant periods are computed to verify the results of site classification. Finally, combined with all the above results, the recommended site classes of near-fault permanent free-field stations are given.

Evaluation of the site effects of the Ankara basin, Turkey

“…During the past decades, the effect of local soil conditions is known to have caused serious damage during several earthquakes. Some well known examples include the earthquake in Michoacan, Mexico in 1985 (Kobayashi et al, 1986), Loma Prieta, California, USA in 1989 (Hough et al, 1990), Kocaeli and Düzce, Turkey in 1999 (Rathje et al, 2003), Chi-Chi, Taiwan in 1999 (Rathje et al, 2005) and Wenchuan, China in 2008 (Wen et al, 2010). While there are several other potential factors contributing to damage, the amplification of ground motion due to local site conditions (such as topographical conditions, ground motion resonance and amplification, etc.)…”

Real-time numerical shake prediction and updating for earthquake early warning

“…Waveforms recorded at two adjacent stations may be very different if their site amplification factors are very different. The different site classifications can induce the amplifications of response spectra in different period ranges and have been estimated in the frequency domain in many studies (Nakamura 1989;Zhao et al 2006;Wen 2010).…”

“…We use the definition of NEHRP site classes (Wen et al 2010) based on the site natural period (s). The site are categorized into four classes, named class SC I: (rock/stiff soil) T p \ 0.2 s, SC II: (hard soil) 0.2 s B T p \ 0.4 s, SC III: (medium soil) 0.4 s B T p \ 0.6 s, SC IV: (soft soil) T p C 0.6 s. The average response spectra H/V ratio for the four classes above is calculated by 204 records of Wenchuan earthquake data, and it is shown in Fig.…”

A study of site response in the Longmen Shan and adjacent regions and site response models for the Sichuan Basin

“…Developing regional models to account for the site response effects can be challenging due to the varying geological structures beneath the seismic stations. Correction factors based on Vs. 30, which is the averaged shear-wave velocity in the top 30 m under the site, are usually adopted in ground motion prediction equations to account for the site effects (Wen et al, 2010;Bora et al, 2016;Li et al, 2018a;Stewart et al, 2020;Xu et al, 2020).…”