Seismic site classification and correlation between V-S and SPT-N for deep soil sites in Indo-Gangetic Basin

Bajaj, Ketan and Anbazhagan, P (2019) Seismic site classification and correlation between V-S and SPT-N for deep soil sites in Indo-Gangetic Basin. In: JOURNAL OF APPLIED GEOPHYSICS, 163 . pp. 55-72.

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Abstract

The Indo-Gangetic Basin (IGB) is occupied by the thick deposits of different types of loose to dense soil due to the active sedimentation. Till date, no detailed study has been carried out on seismic site characterization, and classification considering shear wave velocity >50 m depth. In this study, surface wave survey was used for determining the shear wave velocity (V-S) variation with depth at 276 locations in the IGB using low-frequency geophones by performing combined active (Multichannel analysis of surface waves, MASW) and passive (Ambient Noise) surveys. To study the spatial variability of V-S, based on the sediment deposition and geological variability, the whole IGB has been divided into Punjab-Haryana region (PHR), Uttar Pradesh region (UPR), and Bihar region (BR). Firstly, using the least square, orthogonal, and mixed effect approaches, a new correlation between the V-S and SPT-N has been developed for all the three regions separately. The V-S and SPT-N correlation has been developed considering both corrected and uncorrected SPT-N value. The residuals have been determined using the observed and the predicted V-S values from newly developed V-S and SFT-N correlation from each approach. For the same SPT-N value, correlation for UPR region is predicting high V-S value as compared to other two regions. Studying the variation of residuals with V-S, it is determined that the mixed effect is performing better for V-S <= 250 m/s and orthogonal for V-S > 250 m/s. At higher N-value, difference between V-S values for all the three regions are noticeable. Further, the newly developed relationships are compared with the existing V-S and SPT-N relationship. Additionally, the IGB is classified based on the average shear wave velocity in the top 30 m (V-S30) as per the National Earthquake Hazards Reduction Program (NEHRP) and compared with Eurocode 8 (EC8). The V-S30 is high in the southern part of the BR and UPR and low near to the active channel deposition and major part of the IGB is classified as seismic site class D. Most of the IGB sites have experienced severe damage either due to local site effects or liquefaction during past earthquakes. Therefore, the spatial variability of the average shear wave velocity at different depths, i.e., at top 5,10,1520, 30 50, 100, 150, 200, 250 and 300 m are also estimated and compared with the available basement depth map. (C) 2019 Published by Elsevier B.V.

Item Type:	Journal Article
Publication:	JOURNAL OF APPLIED GEOPHYSICS
Publisher:	ELSEVIER SCIENCE BV
Additional Information:	copyright this article belongs to ELSEVIER SCIENCE BV
Keywords:	Seismic site classification; V-S and SPT-N correlation; V-S30; Indo-Gangetic basin; Deep sedimentary deposits; Surface wave methods
Department/Centre:	Division of Mechanical Sciences > Civil Engineering
Date Deposited:	26 Jun 2019 17:11
Last Modified:	26 Jun 2019 17:11
URI:	http://eprints.iisc.ac.in/id/eprint/63085

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