Volume No. 9 Issue No.: 2 Page No.: 446-453 October-December 201

 

EARTHQUAKE HAZARD ASSESSMENT IN KACHCHH SEISMIC ZONE, GUJARAT, INDIA : USING AMBIENT NOISE MEASUREMENT TECHNIQUES

 

Shukla Arjav * and Thakkar M.G.

Department of Earth & Environmental Science, KSKV Kachchh University, Bhuj-Kachchh, Gujarat (INDIA)

 

Received on : July 10, 2014

 

ABSTRACT

 

Microzonation practice in seismically active regions like Kachchh, India has been an essential, advantageous and predictive application to study the behavior and estimation of local sites. The fundamentals of site response studies are to estimate the response of a particular site to seismicity in the earthquake prone regions. In recent years, a sum up of specified relative techniques and operations for microzonation in reference of site response has been established. The relative techniques for microzonation studies in civil engineering practice are Ambient Noise measurements, Multichannel Analysis of Surface Waves (MASW), Borehole Logging (PS Logging) etc. have been established to validate the response of a particular site to seismicity. Ambient Noise measurement practice is relatively an inexpensive technique for microtremor recording in site response study, apart from other relevant microzonation practices. The seismic vibrations and emplacements of ambient noise oscillations due all three horizontal to vertical (H/V ratio) components are characterized by dominant soil properties of the particular site. Since the region of Kachchh is considered as intra-plate seismic zone, site response studies are required to be undertaken. The Kachchh basin has short recurrence for large to strong earthquake, hence the vulnerability study in urban, semi-urban and coastal industrial regions are needed to mitigate seismic hazard. In the present study a geophysical instrument, City Shark-?? is used to carry out the ambient noise measurement survey. The site response data collected from varied rock units of Kachchh including sandstones, limestones and shales of Mesozoic to Cenozoic time. Further, the data also collected from soft sediments of the plain of Banni and the Great Rann of Kachchh to understand frequency amplitude variation in varied deposits. It is found that soft sediments show more amplitude variation compared to the hard rocks, irrespective of the hard rock lithologies and gain of the microtremor recorder. Hence, the sites, which are places on Quaternary sediments with > 3m thickness and hard rock basements, are vulnerable for seismic hazards in active intra-plate basin like Kachchh.

 

Keywords : Ambient noise, H/V Ratio, Microzonation, Kachchh Seismic Zone, City Shark-II, Seismic hazard

 

 

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