Delhi has more seismic recorders than anywhere else in the country, with 16 of the total 115 detectors having been installed in the national capital.
Earthquakes in Delhi: Since May, Delhi and surrounding areas have experienced 11 minor earthquakes, with the most recent being a 2.1 magnitude one on Monday. The most powerful of these minor earthquakes was one with the magnitude of 3.4. The series of earthquakes has caused people to discuss whether the seismicity in Delhi has increased and speculate that a bigger earthquake is coming, according to a report in IE. However, these apprehensions seem to be without any reason, the report added.
Are so many earthquakes in Delhi unusual?
According to the report, scientists have said that in the last few months, Delhi has not witnessed any unusual seismic activity. The report quoted former head of Delhi’s National Centre for Seismology and currently working at National Geophysical Research Institute (NGRI) in Hyderabad Vineet Gehlot as saying that Delhi and surrounding areas, which includes Ajmer, the Aravallis, Mount Abu and Jaipur, experience about two to three earthquakes of 2.5 magnitude or higher every month. However, they can vary monthly or annually, he said, adding that seismological and geological processes are not very smooth, so witnessing a higher number of cases sometimes is not unexpected.
The report also stated that the detection of earthquakes also depends on the number of seismometres installed in the area. Delhi has more seismic recorders than anywhere else in the country, with 16 of the total 115 detectors having been installed in the national capital. Therefore, even the minutest of earthquakes, which are not even felt by people, are recorded, the report added.
Are the small earthquakes a sign of a bigger one coming?
The report states that earthquakes below the magnitude of 4.0 barely cause any damage. It added that such earthquakes are recorded in thousands all over the world every year and they do not foretell any bigger earthquakes. Former NGRI director and an expert on earthquakes Harsh Gupta was quoted by the report as saying that the concept of foreshocks is usually applied in hindsight and when a big event happens, all smaller earthquakes in the region are usually classified as foreshocks. Foreshocks, he said, are post-event definitions.
He further said that a big event might occur, and it cannot be ruled but they cannot be predicted on the basis of small earthquakes.
Earthquakes in Delhi: The signal to an upcoming earthquake?
The report stated that scientists have for years been working on identifying the signs for an earthquake, but have not had any success so far. Only some special earthquakes, which are usually triggered by volcanic eruptions, can be predicted to some extent, the report stated, adding that according to Gehlot, these earthquakes are more “well-behaved” than others.
Moreover, Gehlot said, predicting earthquakes in Delhi is even harder since the city does not lie on any fault lines, unlike Himalayan region, where understanding of tectonics is a little better due to it being located in a region where two tectonic plates meet each other. The Himalayan region, the report added, is one of the most seismically active regions in the world.
Is a big earthquake coming in Himalayan region?
Scientists believe that the region might witness a major earthquake of magnitude 8 or higher. The conclusion has been reached after scientists were able to measure the tension building up under the surface due to one tectonic plate trying to move underneath the other. However, scientists do not know when this major earthquake will occur, and the prediction is only based on the estimate of the energy waiting to be released.
The report explained that an earthquake of magnitude 6.0 is typically linked with the energy that was released by the atom bomb dropped over Hiroshima. Moreover, the magnitude of earthquakes is measured on a logarithmic scale, the earthquake of 7.0 magnitude would be 32 times more powerful than a 6.0 magnitude one, and a quake of 8 magnitude would be nearly 1,000 times more powerful than a 6.0 magnitude earthquake.
The report quoted Gupta as saying that the argument of smaller earthquakes helping release energy little by little also does not hold, since Delhi has not witnessed any earthquakes of 5.0-6.0 magnitudes in the last 50-60 years and in order to release the energy equal to a 6.0 magnitude earthquake, a thousand 4.0 magnitude quakes would be needed.
Is a big earthquake coming to Delhi?
While the report quoted Gupta as saying that they do not know, he further asked that even if we did know about an upcoming earthquake, what could be done about it. The entire city could not be evacuated even if the exact time of the earthquake was known, he said, adding that prediction would not make the people safe against earthquakes. What is needed, he said, are earthquake resistant structures, information about drills during the occurrence and knowledge about the safe places to run to.