Shallow Sedimentary Structure of the Brahmaputra Valley Constraint from Receiver Functions Analysis

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• 作者：Sowrav Saikia ; Sumer Chopra ; Santanu Baruah…
• 关键词：Brahmaputra Valley ; Receiver function inversion ; Neighborhood Algorithm (NA) ; sedimentary structure
• 刊名：Pure and Applied Geophysics
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：174
• 期：1
• 页码：229-247
• 全文大小：
• 刊物类别：Earth and Environmental Science
• 刊物主题：Geophysics/Geodesy;
• 出版者：Springer International Publishing
• ISSN：1420-9136
• 卷排序：174

文摘

In this study, receiver functions from ten Broadband seismograph stations on Cenozoic sediment formations of Brahmaputra valley and its neighboring region in northeastern part of India are determined. Receiver function traces from this region show delay in peak by 1–2.5 s and associated minor peaks with the direct P-phase peak. Based on such observation, we try to image sedimentary structure of the Brahmaputra valley plain, adjacent Shillong plateau and Himalayan foredeep region. An adapted hybrid global waveform inversion technique has been applied to extract sedimentary basin structure beneath each site. The sedimentary cover of the basin is about 0.5–6.5 km thick across the valley, 0.5–1.0 km on Shillong plateau and 2.0–5.0 km in nearby foredeep region. We have found that sedimentary thickness increases from SW to NE along the Brahmaputra valley and towards the Eastern Himalayan syntaxes. The estimated sediment thickness and S wave velocity structure agree well with the results of previous active source, gravity, and deep borehole studies carried out in this region. The thick crustal low velocity sediment cover in Brahmaputra valley is expected to amplify ground motions during earthquakes and therefore important for seismic hazard assessment of the region.