Microzonation of Earthquake Hazards

Introduction

Many earthquakes in the past have left many lessons to be learned which are very essential to plan infrastructure and even to mitigate such calamities in the future. The hazards associated with earthquakes are referred to as seismic hazards. The practise of earthquake engineering involves the identification and mitigation of seismic hazards. Microzonation has generally been recognized as the most accepted tool in seismic hazard assessment and risk evaluation. It is defined as the zonation concerning ground-motion characteristics taking into account source and site conditions. Making improvements on the conventional macrozonation maps and regional hazard maps, the micro zonation of the ar region generates detailed maps that predict the hazard at much smaller scales. Seismic microzonation is the generic name for subdividing a region into individual areas having different potentials hazardous earthquake effects, defining their specific seismic behaviour for engineering design and land-use planning.

Fundamentals

The basis of microzonation is to model the rupture mechanism at the source of an earthquake, evaluate the propagation of waves through the earth to the top of bedrock, determine the effect of the local soil profile and thus develop a hazard map indicating the vulnerability of the area to potential seismic hazard. Seismic microzonation will also help in designing buried lifelines such as tunnels, water and sewage lines, gas and oil lines, and power and communication lines.
Seismic microzonation is defined as the process of subdividing a potential earthquake-prone area into zones concerning some geological and geophysical characteristics of the sites such as ground shaking, liquefaction susceptibility, landslide and rockfall hazard, earthquake-related flooding so that seismic hazards at different locations within the area can correctly be identified. Microzonation provides the basis for site-specific risk analysis, which can assist in the mitigation of earthquake damage.

Effect of Site Conditions on Earthquake Ground Motion

It has long been recognized that the intensity of ground shaking during earthquakes and the associated damage to structures are significantly influenced by local geologic and soil conditions. Unconsolidated sediments are found to amplify ground motion during earthquakes and are hence more prone to earthquake damage than ground with hard strata. Modern cities built on soft sediments are especially vulnerable to damage caused by amplified ground motions.

Conclusion:

Dynamic characteristics of the site such as predominant period, amplification factor, shear wave velocity, standard penetration test values can be used for seismic microzonation purpose. Microtremor observations are easy to perform, inexpensive and can be applied to places with low seismicity as well; hence, microtremor measurements can be used conveniently for microzonation.In a nutshell, microzonation is the need of the hour to deal with such terrible and devastating disasters.


WRITTEN BY: Biswajit Sahoo and Debasish Beria


Comments

Post a Comment

Popular posts from this blog

Tackling the storm

Image
CYCLONE RESISTANT BUILDING CONSTRUCTION Cyclones have been an inescapable situation in India, especially in the eastern states of Odisha, West Bengal, and Andhra Pradesh. This calls for the construction of cyclone-resistant buildings in cyclone-prone areas to avoid loss of life and property. Low-lying coast areas, river floodplains, and sea-shore areas are highly vulnerable to cyclones. Certain settlement pattern even causes "funnel effect" which results in greater damage. While it's a common belief that heavier buildings are safer, in reality, a well built and engineered house provides better safety. Minimum standards for the design, construction, and performance of buildings to withstand extreme climate-related natural hazard events depending upon their locations should be set. We know cyclones are beyond human control but measures can be taken to reduce the loss of lives like evacuating people to safe areas, quick recovery of important fa
Read more

Central Vista Project: Transforming the Political Face of India, the Civil Way

Image
    Source: Wikipedia     Central Vista Redevelopment Project  refers to the ongoing  redevelopment  to revamp the Central Vista, India's central administrative area located near  Raisina  Hill, New Delhi . The area houses India's government and parliamentary offices and has  been  described as the "power corridor" of the country. The project seeks to improve infrastructure for the Government of India, including retrofitting and refurbishing some heritage buildings to make them functional and safe.        Source: The Hindu   The Central Vista Redevelopment Project was launched in 2019 .   The project includes converting North and South Blocks into public museums while creating an ensemble of new secretariat buildings to house all ministries, relocating the Vice President and the Prime Minister's offices  and residences near the North and South Blocks, and revamping the 3 km (1.9 mi) long  Rajpath  between  Rashtrapati  Bhavan  and  India Gate .   A new Parliament
Read more

Demolition of Building Structures

Image
Demolition of a building is the process of dismantling or destroying a structure after its life of serviceability by pre-planned and controlled methods. It is the science and engineering in safely and efficiently tearing down buildings and other artificial structures . The tallest planned demolition of a building was the 47-storey Singer Building in New York City , built-in 1908 and torn down in 1967–1968 to be replaced by One Liberty Plaza Building Demolition methods: There are two types of demolition methods used for buildings and structures, Non-explosive demolition and Explosive demolition. In the non-explosive method, demolition of a structure is done with some equipment, without the use of any explosive. In contrast, in the explosive method, demolition is done with the help of bombs and explosives. Building Demolition Process: Different steps are involved in the process of demolition of building structures. They are: 1. Surveying 2. Removal of hazardous materials 3
Read more