Natural Disasters

Triple tremors in Delhi: ‘We should always be prepared for a big earthquake’

Poorly constructed houses in crammed colonies can present tough challenge      

By Seema Prasad
Published: Wednesday 16 November 2022

Nepal witnessed three earthquakes November 9, 10 and 12, which led to tremors in Delhi and other parts of northern India.
Down To Earth spoke to Harsh Kumar Gupta, a Padmashree-winning Indian earth scientist and seismologist, to understand the reasons behind this occurrence.

Gupta is a member of the Atomic Energy Regulatory Board, president of the Geological Society of India and editor-in-chief of the Encyclopedia of Solid Earth Geophysics.

Seema Prasad: Last week we had three earthquakes in Nepal causing tremors across India. What is causing them?

Harsh Kumar Gupta: If you remember, we had an earthquake on the India-Nepal border on April 25, 2015 of 7.8 magnitude. Seventeen days later, the region experienced another earthquake of 7.3 on May 12 and the aftershocks continued for quite some time after that. 

The activity happening now is close to those quakes. At the same time, these quakes could also be foreshocks of larger quakes. 

One major problem in seismology is we cannot say for sure if some activity is an aftershock or foreshock. Furthermore, it cannot be ruled out that these are independent quakes on their own too. One cannot make any conclusions.

For the Delhi region, earthquakes in the range of 4-4.5 magnitude are very common. In the last 100 years, about 25-30 such earthquakes have already happened in Delhi without significant damage. So, this is not unusual. What is unusual is that no major earthquake of magnitude 6 has been felt in Delhi thus far.

SP: Do the earthquakes of the last week signify anything for us in Delhi beyond this?

HKG: Earthquakes commonly occur in the Himalayas and will continue to occur. But it must be remembered that we have not had a severe earthquake since the 1950 Assam-Tibet earthquake of magnitude 8.6 in the Himalayan range. 

However, these minor earthquakes are just a reminder and indication that a big earthquake can occur at any time. That is about it. 

Theoretically, the situation would be very bad, particularly in locations like Delhi, which has small, little colonies with poorly constructed two to three-story houses, built without earthquake-resilience in mind.

Earthquakes cannot be predicted and we can never say for sure. But for instance, tomorrow if there was an earthquake of magnitude 8 about to take place in the vicinity of Delhi, 200-300 kilometres away by 12 noon, how fast would the residents be able to evacuate? 

It would result in 50,000-60,000 casualties in the National Capital Region. In fact, this is why we have to learn to live with earthquakes as a reality. It all boils down to preparedness and awareness right from school. 

We could also have an Earthquake Week or Day to build consciousness. In Nepal, for instance, they observe Earthquake Day on January 15 every year to pay tribute to the tragedy of the 1934 Nepal-India earthquake. 

In Kathmandu, they located 100 spots that are designated safe places for people to run to during a quake. In Delhi, the government could try something similar. 

SP: Has there been an increase or decrease in seismic activity in the Himalayas in the last few decades?

HKG: We have not had a magnitude 8 earthquake in the Himalayas since 1950. Only three earthquakes of magnitude 7.5 or more have occurred in the Himalayas since the 1980s. These were the 1988 earthquake in northeast India, the 2005 earthquake on the Muzzafarabad-Pakistan border and the Nepal earthquake in 2015.

Moreover, there are phases of ‘seismic quiescence’ and ‘seismic activity’ in earthquake belts. The Himalayas, by and large, is currently in a ‘seismic quiescence’ phase, which indicates a relative decrease in seismic activity. 

SP: Recently, there was a 6.1 magnitude earthquake in Japan. Could that have potentially impacted India? Earthquakes in which other geographies could impact India?

HKG: Theoretically, there could be an effect in India in case of a great earthquake in Japan. The 2004 Sumatra earthquake in Indonesia, for instance, created a huge tsunami claiming some 20,000 lives in India.

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