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Earthquakes: How safe are buildings in India? (a very important and timely article about India)

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Earthquakes: How safe are buildings in India? (a very important and timely article about India) Empty Earthquakes: How safe are buildings in India? (a very important and timely article about India)

Post by Seva Lamberdar Fri Feb 10, 2023 8:46 am

courtesy Vibha Sharma 
(The Tribune, Chandigarh: full reference to the article at the bottom of page*)

Two devastating earthquakes measuring 7.8 and 7.5 in magnitude flattened multiple buildings, killing thousands of people across southern Turkey and northern Syria.

According to reports, some of the new buildings also crumbled under the impact, raising questions about building safety standards in Turkey. Ideally, technology and building rules should have ensured that buildings withstand earthquakes of higher magnitudes.

Seismicity (earthquakes) and Indian subcontinent:

While there have been several minor/moderate quakes in the region, the last devastating episode in the series in the Indian subcontinent were the two back-to-back shockers measuring 7.8 and 7.3 on the Richter followed by several high-intensity ones in April 2015.

They caused damage worth $10 billion, killing around 9200 persons according to the available data in Nepal.

The subcontinent is sitting on the highly seismic Indian plate, with some major fault lines.

Active thrust faults exist all across foothills in North India, the North-East and into northern Pakistan. Major faults exist from North-West to East and the North-East in India.

Some of the faults in the 1905 Kangra earthquake measuring 8 on the Richter scale and the 1934 along Bihar-Nepal Border measuring 8.4.

Experts say that there is no seismically (earthquake) safe zone in India.

The Indian plate is one of the 12 major plates locked together to the surface of the earth like a jigsaw puzzle.

The Indian plate boundary has become very active of late and is gradually moving, pushing against the Eurasian plate by 4 to 5 cm every year.

If the recent incidents in Joshimath are any indication, mountains are becoming increasingly restless.

In the North, areas south of the Himalayas and Indo-Gangetic plains, including parts of Punjab, Haryana, Himachal, Delhi, Uttaranchal and Uttar Pradesh, are vulnerable.

With many areas in the high seismic activity zones IV and V, this should be a major cause of worry for the planners.

Seismic (earthquake) zones in India:

India is divided into four seismic zones —Zone-II to Zone V.

Very high risk Zone V with the highest seismic intensity comprises the north-eastern areas, parts of Jammu and Kashmir, Himachal Pradesh, Uttaranchal, Rann of Kutch and north Bihar.

High risk Zone-IV covers the remaining parts of Jammu & Kashmir and Himachal Pradesh, Union Territory of Delhi, Sikkim, northern parts of Uttar Pradesh, Bihar and West Bengal, parts of Gujarat, some parts of Maharashtra near the west coast and Rajasthan.

Moderate risk Zone-III includes Kerala, Goa, Lakshadweep islands, the remaining parts of Uttar Pradesh, Gujarat and West Bengal, parts of Punjab, Rajasthan, Madhya Pradesh, Bihar, Jharkhand, Chhattisgarh, Maharashtra, Orissa, Andhra Pradesh, Tamil Nadu and Karnataka.

The rest of the country is Zone-II.

Almost 59 per cent of India is prone to earthquakes of different magnitudes—11 per cent in Zone V, 18 per cent in Zone IV and 30 per cent in Zone III.

Buildings and earthquakes:

Strange as it may sound, earthquakes do not kill, it is the structurally unsound buildings that do. Experts say earthquakes are a hazard that need not get converted into a disaster if buildings are safe, everyone follows the law and there is a -drafted disaster management plan in place.

While India has National Building Code and stringent rules and regulations related to constructing safer buildings, the question is the implementation.

India has well developed BIS and earthquake resistant guidelines. The 1962 guidelines were revised in 2002 after the devastating Bhuj earthquake resulting in devastation and death toll (anywhere between 13,805 and 20,023) of unimaginable order.

Building safety guidelines deal with earthquake-resistant construction—design, construction, improving earthquake resistance, repair and seismic strengthening of buildings etc.

Contrary to popular belief, a structurally sound high-rise is safer than an unscientifically constructed single-storied house.

During an earthquake, a building experiences transverse and longitudinal vibrations.

As the ground moves randomly, the top weight vibrates accordingly.

Any building constructed under the supervision of structural engineers with attention to material grades and designs to ensure its movement as a single unit in the event of an earthquake will be able to sustain the impact due to uniformity of structure.

While new buildings can be made safe by following the laws, structural strength and stability of old ones can also be improved with the help of retrofitting (later fixing), etc.

However, the problem is most Indian cities have been urbanised in the most haphazard and unorganised way and buildings constructed in clear defiance of laws.

*Ref.: Vibha Sharma (The Tribune), "Earthquakes: How safe are buildings in India?", Feb. 10, 2023,  https://www.tribuneindia.com/news/nation/earthquakes-how-safe-are-buildings-in-india-478501
Seva Lamberdar
Seva Lamberdar

Posts : 6512
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https://docs.google.com/document/d/1bYp0igbxHcmg1G1J-qw0VUBSn7Fu

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Post by Seva Lamberdar Fri Feb 10, 2023 3:02 pm

While the accurate prediction of earthquakes well ahead of time (to give advance warning adequately) is highly unlikely in the near future, there are steps people and Govts. can take to minimize property damage and human injury and death due to earthquakes.

This will require the proper implementation of building code (especially by incorporating the seismic code) in the design and construction of new buildings, while retrofitting (fortifying and updating) the old buildings so as to bring them up-to-date against potential seismic activity.

This naturally involves strict implementation of seismic code not only in the design of buildings but also during their construction and maintenance (using right materials and construction methods and timely maintenance etc., as recommended based on the seismic code). A general public awareness is very much needed in this regard.
Seva Lamberdar
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Post by Seva Lamberdar Sun Feb 12, 2023 5:56 pm

Please check out the following link for additional comments / responses: 
 http://creative.sulekha.com/how-safe-are-buildings-in-india-against-earthquakes-a-very-important-and-timely-article-for-indians_641790_blog
Seva Lamberdar
Seva Lamberdar

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