Seismic Site Classification and Site Period Determination of NIT Silchar Using MASW

Abstract

Silchar is situated in the north-eastern region of India which comes under seismic zone-V. This region of India is bounded by several faults like Dauki fault, Indo-Myanmar subduction zone and Sitakunda–Teknaf fault. Most of the buildings in Silchar including some buildings at NIT Silchar developed cracks during Imphal Earthquake of magnitude Mw = 6.7 on 4th January 2016. Hence, seismic site classification becomes very crucial for the entire north-east region. In the present study, NIT Silchar campus has been taken as a study area. Multichannel analysis of surface waves (MASW) technique, one of the recent developments in geophysical methods, was carried out at nine sites within the campus and the average shear wave velocity (Vs30) upto 30 m depth was obtained. Three confirmatory boreholes were dug for validation. The study showed that NIT Silchar falls under seismic site class D category according to National Earthquake Hazards Reduction Program (NEHRP) Code. The fundamental site period obtained from MASW reveals that, the soil conditions at NIT Silchar pose a potential threat to four- and five-storey buildings due to resonance during earthquakes.