Estimation of site response function using Nakamura technique: a case study from Kumaun Himalaya

Abstract

The aim of this study is accomplished by utilizing the H/V spectral ratio method (Nakamura technique) to investigate the site response at fifteen seismic site stations. Regarding this method, some significant local site parameters such as the fundamental frequencies (f0) of soft sediments, peak amplitudes (A0) corresponding to H/V spectral ratios, spectrum amplitude, and spectrum rotation were computed over fifteen seismic site stations in the study area. A site response study has been done by using microtremor data from fifteen seismic site stations. The fundamental frequency response varies from 0.67 to 11.54 Hz within the study area. Resulting from this analysis, the fundamental frequency response is low in and around the KHAT, PNGL, and SBLA seismic site stations, which indicates the possibility of thick sedimentary soil cover at greater depth. Similarly, the peak amplification at these seismic site stations is found to be in the range of 2–4. Further, the contour map is prepared with the help of fundamental frequency response values obtained from the H/V curve to observe the area of seismic hazard potential in the study region. Also, obtained H/V results from different seismic site stations were verified by considering the SESAME guidelines and conditions for reliability. Then, spectrum rotation and spectrum amplitude analysis were carried out to know the characteristics of H/V with respect to azimuth and frequency in the sedimentary soil.