• RICHA KUMARI

Articles written in Journal of Earth System Science

• Role of site effect for the evaluation of attenuation characteristics of P, S and coda waves in Kinnaur region, NW Himalaya

The site effect and attenuation studies are carried out for Kinnaur region of northwest Himalaya, India. A total of 109 local events happened in Kinnaur region of magnitude range 1.6–4.5, are utilized for present work. The earthquake records are influenced by the site effect depending on soft sediment thickness beneath the recording sites. Therefore, in the present study, records are corrected for site effects to estimate P ($Q_{p}$), S ($Q_{s}$) and coda ($Q_{c}$) wave quality factor. The regional frequency dependent attenuation relations, i.e., $Q_{p}$(f)$=$(29$\pm$1)$f^{(1.01±0.05)}$, $Q_{s}$ (f)$=$(38$\pm$5)$f^{(1.1±0.06)}$ and $Q_{c}$(f)$=$(74$\pm$11)$f^{(1.17±0.01)}$ are established for the Kinnaur region. The Kinnaur Himalaya mainly belongs to Higher Himalaya Crystalline (HHC) and Tethys Himalaya, where these two geological units are differentiated by the South Tibetan Detachment System (STDS). The resonance frequencies and attenuation characteristics are estimated for both regions, i.e., HHC and Tethys Himalaya. A comparison is made between HHC and Tethys Himalaya in the form of resonance frequencies and attenuation properties. The low value resonance frequency and high rate of attenuation towards the northern side of STDS, i.e., Tethys Himalaya support the presence of low-grade metasedimentary rocks. It suggests that Tethys Himalaya has high seismic hazard potential zone compared to HHC.

$\bf{Highlights}$

$\bullet$Site effects have been incorporated to estimate attenuation characteristics of P, S and coda waves in Kinnaur region, NW Himalaya.

$\bullet$The regional frequency dependent attenuation relations i.e., $Q_{p}$(f)=(29$\pm$1)$f^{(1.01±0.05)}$, $Q_{s}$ (f)=(38$\pm$5)$f^{(1.1±0.06)}$ and $Q_{c}$(f)=(74$\pm$11)$f^{(1.17±0.01)}$ are established for the Kinnaur region. The close resemblance of resonance frequencies with the geology of the study region has been observed.

$\bullet$The Tethys Himalaya lies in present study region has high seismic hazard potential zone as compare to Higher Himalaya Crystalline.

• Characterization of shear wave attenuation and site effects in the Garhwal Himalaya, India from inversion of strong motion records

The frequency-dependent shear-wave quality factor (Q_\beta(f )) and site amplification are computed for the seismically and tectonically active Garhwal Himalaya. The inversion technique of strong motion data is applied to obtain Q_\beta(f ) and site effect at each recording station. The strong motion data of 82 earthquakes recorded in the Garhwal region is used for the present inversion algorithm. The comparison of site effects obtained by the present inversion scheme and well developed H/V technique (H/V is the ratio of Fourier spectra horizontal to vertical components) shows that site effects computed through the inversion technique have close resemblance with these estimates from the H/V technique. Both horizontal components are used to establish the frequency-dependent Q_\beta(f ) relations at each station. The values of ‘Q_o’ and ‘n’ at different stations vary from 92 to 112 and 0.9 to 1.1, respectively. The close resemblance of obtained Q_\beta(f ) relations at different stations suggest, the presence of almost similar type of lithology, i.e., hard rock at these stations. A regional quality factor relationship of form, Q_\beta(f ) = (102 ± 3.9)f^(1.0±0.1) is established for the Garhwal Himalaya based on modelled Q_\beta values of each station. This relationship reveals low Q_o value (${\le}$200) and high n value (${\ge}$0.8) for the Garhwal Himalaya, which correspond to tectonically and seismically active region.

$\bf{Highlights}$

$\bullet$ The frequency-dependent shear-wave quality factor and site amplification are computed simultaneously for the Garhwal region, NW Himalaya.

$\bullet$ A regional quality factor relationship of form, Qβ(f) = (102 ± 3.9)f(1.0±0.1) is established for the Garhwal Himalaya.

$\bullet$ The acceleration records corrected from the obtained site effect are used to develop attenuation relations at each recording station.

$\bullet$ The close resemblance of obtained Qβ(f) relations and the geology has been observed for the study region.

• # Journal of Earth System Science

Volume 131, 2022
All articles
Continuous Article Publishing mode

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019