Earthquakes - Staying stable on unstable grounds

At 7:51 am on 28 April 2021, Assam was struck by a massive earthquake of 6.4 magnitude on the Richter scale, according to the National Center for Seismology. The earthquake was felt in the entire northeast region of India and some parts of Bihar and West Bengal. A total of six aftershocks of magnitude ranging 3.2 to 4.7 on the Richter scale were felt within three hours from the time of occurrence of the main shock of 6.4. 

The Bureau of Indian Standards has classified regions in India into four seismic zones. These are, zones II (low intensity), III (moderate intensity), IV (severe intensity) and V (very severe intensity). Among these, zone V is the most seismically active region and zone II is the least active. Northeast India falls under ‘Seismic Hazard Zone V’ and is also one of the six most seismically active regions of the world. The northeastern region is also associated with collisional tectonics where Indian plate subducts beneath the Eurasian Plate. 

Earthquake hazards in the northeastern region and elsewhere cannot be predicted, however the disaster can be mitigated. To reduce the potential for human, material, or environmental losses caused by earthquakes, modern disaster management goes beyond post-disaster assistance and includes pre-disaster planning and preparedness activities, organisational planning, training, information management etc.

Preparing ahead 

The impact of an earthquake can certainly be minimised with proper preparation. For this purpose, consulting structural engineers and designing the infrastructure of our cities to be earthquake resistant can help in long term prevention from earthquakes. Damage to buildings is a serious cause of human injury and death during an earthquake. For old homes, it is advised to know whether it complies with the National Building Codes (NBC) to identify potential weaknesses. One should closely inspect their house and also their workplace to determine if there are structural dangers such as cracks on walls and ceilings and work towards repairing them. Fastening shelves securely to walls and placing heavy/large objects on lower shelves also helps in preventing damage during an earthquake.

When an earthquake does strike, remember the Drop-Cover-Hold technique. Drop on your hands and knees, Cover your head and neck with your hand and seek shelter under a table or sidle up to the interior wall, away from tall objects that might topple. Hold onto the leg of a table or if you’re outside continue to shield your head and neck with your arms. Even after an earthquake subsides, one has to be careful of the aftermath including aftershocks. One shouldn’t enter damaged buildings, and if stuck in rubble, make sure to protect the nose, mouth and eyes from dust. Make noise by whistling or tapping on a surface to get attention. When outside, one should be careful from hazards like fallen electrical lines, ruptured gas pipes etc.

Towards a quake- resilient future 

Frequent earthquakes have increased the importance of mainstreaming earthquake resistant infrastructure in India. Several codes on earthquake engineering have been produced in construction of quakeresistant structures and regarding tests & measurements therewith by the Bureau of Indian Standards. Various mechanisms have been adopted while designing buildings which make them more earthquake resistant, such as bracing, base isolation, dampers etc, to enhance building vibration control. Vibration control is the reduction of desired building structural response to earthquake or wind forces on the structure. 

One should also be aware of the necessary compliances and guidelines while making buildings. Awareness regarding prevention methods during an earthquake along with relief and reconstruction is a must for people. Continuous inspection and care of buildings is also critical in minimising damage from earthquakes. An earthquake can strike anytime but it's upon ourselves to be prepared for tomorrow which can help to save our present. 

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