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Seismic Microzonation reports for Delhi and Kolkata
Mar 22, 2016

Union Minister for Science & Technology and Earth Sciences released Seismic microzonation reports for Delhi and Kolkata in New Delhi.

What help these programme do

such scientific endeavours should help to minimize the impact of earthquakes by

(a) Proper assessment of Seismic Hazard

(b) Implementation of safe building construction codes, and 

(c) adopting appropriate land-use planning

What is Microzonation: Prediction of most of the natural events, particularly the earthquakes, is not possible, but the resulting damage due to them can be minimized by taking proper measures. Microzonation is one such measure where the emphasis on the impact of earthquake on the habitat is given.

Definition: Seismic Microzonation is a process of identifying such related geological, seismological, hydrological and geotechnical site characteristics in a specific region.  These would help design of safe structures to reduce loss of human life.

How process of Microzonation help in lessening impact of earthquake:

It was seen that due to an earthquake in 1985 there was severe damage in Mexico city, though the earthquake source was located about 350 km away from the city. It was realized that putting a large region into a single seismic hazard zone is not a good idea. This and several other examples led to a new concept, called Microzonation.

Practice followed in India: Earlier a seismic zoning map for entire India was prepared and published by  the Bureau of Indian Standards (BIS),classifying the entire country into 4 major groups Zone-V (High intensity) to Zone-II (Low intensity). These zones encompass wider area for which specific design spectra is commonly used, despite geological and geo-morphological variability within the respective zones.

What is done under Microzonation:

Under the microzonation process various investigations are done:

  • Ambient noise survey

  • Multi-Channel Analysis of Surface Waves (MASW) survey

  • In-situ geotechnical testing

  • In-situ seismic measurements etc. were carried out 

After analysis of data sets different maps viz., 

  • Peak Ground Acceleration (PGA

  • Spectral accelerations for different periods

  • Liquefaction potential, predominant frequency

  • Amplification factor

  • Average shear wave velocity at 30 meters depth, geology & geomorphology and projected Hazard Scenarios at GIS platform etc. are prepared.

Beneficiaries of  microzonation maps would include:

  • Disaster Mitigation & Management Authorities

  • Urban Development Authorities

  • Planning, Design & Construction Agencies

  • Risk Assessment to existing life & Property

  • Defense Installations

  • Heavy Industry

  • Public Utilities & Services

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