In the past few weeks, various parts of India have been hit by earthquakes. While they have not caused serious damage, they can be emotionally and mentally traumatising, especially for those who have only
learnt of this natural calamity in school textbooks and haven’t lived through them.
Last evening, August 5, a moderate earthquake measuring 5.0 on the Richter scale struck the northeastern state of Arunachal Pradesh. The tremor’s epicentre was located 60 kilometres north-northeast of Shi Yomi district.
Just weeks ago, on July 16, a 5.1 magnitude earthquake jolted the Upper Siang district in Arunachal Pradesh. Prior to that, a 4.8 magnitude quake struck Assam’s Hailakandi district in April.
In North India, in the early hours of August 2, a 2.9 magnitude earthquake jolted Delhi. Prior to that, in July, a 4.5 magnitude earthquake hit in the Bay of Bengal, and it triggered tremors in parts of Visakhapatnam and adjoining districts of Andhra Pradesh. The tremors were felt in Gajuwaka, Mangalapalem, Sagar Nagar, Pedda Waltair, Arilova, MVP colony, Appughar and other areas.
What is an earthquake?
The U.S. Geological Survey explains an earthquake as what happens when two blocks of the Earth suddenly slip past one another. The surface where they slip is called the fault or fault plane. The location below the earth’s surface where the earthquake starts is called the hypocenter, and the location directly above it on the surface of the earth is called the epicenter.
How is tectonic activity divided in India?
India is divided into four seismic (earthquake hazard) zones by the Bureau of Indian Standards. These zones indicate the expected level of earthquake hazard, with Zone V being the highest risk and Zone II the lowest.
The highest risk, Zone V regions are Assam, Arunachal Pradesh, Manipur, Meghalaya, Mizoram, Nagaland, Tripura, Andaman and Nicobar Islands, parts of Jammu and Kashmir, Ladakh, Himachal Pradesh, Uttarakhand, the Rann of Kutch, Gujarat region and parts of Bihar.
In the High Damage Risk zone (Zone IV) lie parts of Delhi, Punjab, Haryana, Uttar Pradesh, Bihar, West Bengal, Sikkim, parts of Rajasthan, Gujarat, Maharashtra and Jharkhand.
Parts of Karnataka, Tamil Nadu, Telangana, Madhya Pradesh, Chhattisgarh fall in Zone II, while large parts of Kerala, Goa, Madhya Pradesh, Chhattisgarh, Odisha, Andhra Pradesh, Telangana, Karnataka, Tamil Nadu, Maharashtra and parts of northern and western India fall in Zone III, moderate damage risk zone.
How deep in the Earth’s crust do earthquakes occur?
Earthquakes occur in various depth ranges, from 0km to 700 km beneath the Earth’s surface and are divided into three zones: shallow, intermediate, and deep. Shallow earthquakes are generally more dangerous than deep earthquakes. This is because the seismic waves from shallow earthquakes have a shorter distance to travel to the surface, resulting in stronger ground shaking and potentially more damage to structures and greater casualties.
What to do during an earthquake?
Here is what you should do during an earthquake, as recommended by the U.S. Geological Survey:
- If you are INDOORS – stay there! Get under a desk or table and hang on to it (Drop, Cover, and Hold on!) or move into a hallway or against an inside wall. STAY CLEAR of windows, fireplaces, and heavy furniture or appliances. GET OUT of the kitchen, which is a dangerous place (things can fall on you). DON’T run downstairs or rush outside while the building is shaking or while there is danger of falling and hurting yourself or being hit by falling glass or debris.
- If you are OUTSIDE – get into the OPEN, away from buildings, power lines, chimneys, and anything else that might fall on you.
- If you are DRIVING – stop, but carefully. Move your car as far out of traffic as possible. DO NOT stop on or under a bridge or overpass or under trees, light posts, power lines, or signs. STAY INSIDE your car until the shaking stops. When you RESUME driving, watch for breaks in the pavement, fallen rocks, and bumps in the road at bridge approaches.
- If you are in a MOUNTAINOUS AREA – watch out for falling rock, landslides, trees, and other debris that could be loosened by quakes.
