Ground Response of Ahmedabad City during Bhuj Earthquake: A Case Study   Jyant Kumar Associate Professor, Civil Engineering Department, Indian Institute of Science, Bangalore jkumar@civil.iisc.ernet.in
			ABSTRACT

The seismogram recorded at Ahmedabad city during the occurrence of Bhuj earthquake was analyzed to compute the response of ground mass up to a depth of 10 meters. The horizontal acceleration and shear stress time histories of the ground mass were computed at various depths. It was seen that the amplification of the earthquake base motion was quite predominant in the upper 4 m thickness of the soil mass near the ground surface. Standard penetration conducted at three different locations, around the area where a majority of the building failures were experienced, revealed the presence of loose sand strata in a soil zone over which most of the building foundations were provided. The failure of the building foundations was anticipated due to (i) the placement of the building foundations at very shallow depths over loose alluvial sand deposits, and (ii) the significant amplification of the earthquake motion in the upper 4 m thickness of the soil mass.

Keywords: damping; earthquakes; elasticity; liquefaction; vibrations.

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