Abstract

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., \( Q_{p} \left( f \right) = \left( {29 \pm 1} \right)f^{(1.01 \pm 0.05)} \), \( Q_{s} \left( f \right) = \left( {38 \pm 5} \right)f^{(1.1 \pm 0.06)} \) and \( Q_{c} \left( f \right) = \left( {74 \pm 11} \right)f^{(1.17 \pm 0.01)} \) 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.

Research Highlights

• Site effects have been incorporated to estimate attenuation characteristics of P, S and coda waves in Kinnaur region, NW Himalaya.
• The regional frequency dependent attenuation relations i.e. Q_p(f ) = (29±1)f^(1.01±0.05), Q_s(f ) = (38±5) f^(1.1±0.06) and Q_c(f ) = (74±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.
• The Tethys Himalaya lies in present study region has high seismic hazard potential zone as compare to Higher Himalaya Crystalline.

中文翻译：

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场地效应在喜马拉雅山西金纳尔地区评估P，S和尾波的衰减特性中的作用

摘要

在印度喜马拉雅西北部的Kinnaur地区进行了场地效应和衰减研究。目前，在Kinnaur范围1.6-4.5范围内发生的总共109个本地事件被用于当前工作。地震记录受站点影响的影响，取决于记录站点下方的软沉积物厚度。因此，在本研究中，对记录的站点影响进行校正，以估计P（Q _p），S（Q _s）和尾气（Q _c）波品质因数。取决于区域频率的衰减关系，即\（Q_ {p} \ left（f \ right）= \ left（{29 \ pm 1} \ right）f ^ {（（1.01 \ pm 0.05）} \），\（ Q_ {s} \ left（f \ right）= \ left（{38 \ pm 5} \ right）f ^ {（1.1 \ pm 0.06）} \）并且为Kinnaur地区建立了\（Q_ {c} \ left（f \ right）= \ left（{74 \ pm 11} \ right）f ^ {（1.17 \ pm 0.01）} \）。Kinnaur喜马拉雅山主要属于高级喜马拉雅山结晶线（HHC）和Tethys喜马拉雅山，这两个地质单元由藏南拆离系（STDS）区分。估计了HHC和Tethys Himalaya这两个区域的共振频率和衰减特性。在HHC和Tethys Himalaya之间以共振频率和衰减特性的形式进行了比较。低值共振频率和朝向STDS北侧的高衰减率，即特提斯喜马拉雅山，支持了低品位的沉积沉积岩的存在。这表明特提斯喜马拉雅山与HHC相比具有较高的潜在地震危险带。

研究重点

• 在喜马拉雅山西北部Kinnaur地区，已经结合了场地效应来估计P，S和尾波的衰减特性。
• 取决于区域频率的衰减关系，即Q _p（f ）=（29±1）f ^{（1.01±0.05）}，Q _s（f ）=（38±5）f ^{（1.1±0.06）}和Q _c（f ）=（^{在Kinnaur地区建立了}74±11）f ^{（1.17±0.01）。}
• 已经观察到共振频率与研究区域的地质情况非常相似。
• 特提斯喜马拉雅山位于目前的研究区域，与高喜马拉雅山结晶线相比，具有较高的地震危险潜在带。