Site response study based on H/V method using S-wave: A case study in the Kumaon Himalaya, India

Abstract

In this paper, site response study is conducted in highly mountain terrains of the Kumaon Himalaya, India by using Horizontal to Vertical spectral ratio method (H/V) (H/V is ratio of Fourier spectrum of horizontal and vertical component of the record). Strong ground motion data of 110 local earthquakes recorded during year 2006-2013 and the S-phase of these records are utilised to characterize the site effects of the Kumaon Himalaya region. Resonance frequencies at different observation sites are enumerated by using the H/V technique proposed by Nakamura (1989) and later modified by Lermo & Chavez Gaarcia (1993) for S-wave. It is perceived that obtained resonance frequencies vary from one station to another. Recording stations provide different values of resonance frequencies ranging from 0.7 to 8.1 Hz. A close resemblance is observed between resonance frequency and rock type i.e. stations of high values of resonance frequencies are situated at high compact rocks as compared to the stations of low values. Hence, stations having low resonance frequency may be having the potential for high seismic hazard. In the present study, the values of resonance frequencies have increasing trend from south to north direction, which may be the signature of increasing grade of compactness of the rock from south to north. © 2019, Wadia Institute of Himalayan Geology. All rights reserved.