Delhi Earthquakes

What is the issue?

An earthquake of magnitude 2.1 was detected near Delhi on June 08, 2020.
This is the eleventh minor earthquake that is being recorded in and around Delhi since May.

What are the discussions?

These recent earthquakes have triggered discussions on the possibility of increased seismicity around Delhi.
They have also triggered fears of an impending big earthquake soon.
None of these apprehensions has any scientific basis.

Is it unusual for Delhi to experience so many earthquakes?

Nothing unusual - Scientists assert that no unusual seismic activity is taking place around Delhi in the last few months.
Delhi and its surrounding areas usually experience between two and three earthquakes of magnitude 2.5 and above every month.
But there are monthly and annual variations as well.
Geological and seismological processes are not very smooth.
So nothing special has happened in Delhi in the last couple of months.
Detection - Detection of earthquakes, especially those of smaller magnitude, being recorded in an area also depends on the number of seismic recorders installed in that area.
The area around Delhi has the densest concentration of seismometers in the country, even more than the seismically active Himalayan region.
Out of the 115 detectors installed in India, 16 are in or around Delhi.
As a result, even the earthquakes of smaller magnitude are recorded, and this information is publicly accessible.

Do these small earthquakes foretell a bigger one?

Scientifically - Earthquakes of magnitude 4 or below hardly cause any damage anywhere and are mostly inconsequential for practical purposes.
Thousands of such earthquakes are recorded around the world every year, and most of them are uneventful.
They certainly do not signal any big upcoming event.
Foreshocks -Foreshocks are post-event definitions, which is something that is largely applied in hindsight.
When a big event happens, all the smaller earthquakes that have occurred in that region in the near past are classified as foreshocks.
The description does not exist before any big earthquake has happened.
So, the talk of these being foreshocks of a big earthquake in Delhi have no basis at all.
Reality - A big earthquake might still occur, which no can rule out. But they cannot be predicted.
So to say that these small earthquakes are precursors to the big one is totally unscientific.

What is a signal to an upcoming earthquake?

Scientists have been working for years to identify “precursors” to an earthquake, but have so far met with no success.
Some special earthquakes, triggered by volcanic activity, can be predicted to some extent but nothing else.
Predicting earthquakes in a region like Delhi is all the more difficult because the place does not lie on any fault lines.
We know a little bit about the tectonics in the Himalayan region, where two tectonic plates are meeting each other.
But Delhi is located on a single plate, and the seismic activity is generated by internal deformities.
Therefore, predicting earthquakes in advance is out of the question.

Is a big earthquake coming to the Himalayan region?

Scientists say that the Himalayan region is due for a big earthquake, of magnitude 8 or even higher.
That is because they have been able to measure the energy that is getting trapped under the surface as a result of one tectonic plate trying to move beneath the other one.
Even here, scientists have no idea when this big earthquake will occur.
The prediction about the big one is based only on the estimate of the energy that is ready to be released.
An earthquake of magnitude 6 is typically associated with the kind of energy that was released by the atom bomb in Hiroshima.
An earthquake of magnitude 8 would be almost 1,000 times more powerful than a magnitude 6 event.
Even the argument that the smaller quakes are helping release the energy bit by bit so that a big one would not be necessary does not hold.
1,000 earthquakes of magnitude 4 are needed to release the energy equivalent of a magnitude 6 earthquake. These arguments have no basis.

Is a big earthquake coming to Delhi?

No one knows, but a more relevant question is what even if we knew.
Prediction is not going to make us safe against earthquakes.
It is important that we need to make our structures earthquake resistant, we need to follow prescribed drills when an event happens.
These kinds of discussions are the meaningful ones.
No one is ruling out a possibility of a big earthquake in Delhi.
But they would occur when they have to.

Source: The Indian Express