Why in the News?

A 4.0 magnitude earthquake struck the national capital on 17^th February morning, with the epicentre being located near Durgabai Deshmukh College of Special Education in Dhaula Kuan.

What’s in Today’s Article?

• Introduction (Context, Seismic Activity in India, Aravalli-Delhi Fold, Possibility of Large Earth Quake in Delhi, etc.)

Introduction:

• Delhi is located in a seismically active region, making it susceptible to earthquakes.
• Although most tremors felt in the city originate from far-off places like Afghanistan or the Himalayan region, the recent earthquake originated within Delhi itself.
• The event has sparked discussions about the city's seismic risk, geological features, and the possibility of stronger earthquakes in the future.

Seismic Activity in Delhi:

• Delhi falls under Zone 4 of India’s earthquake hazard map, meaning it is in the second-highest category of risk.
• This classification is based on the MSK scale (Medvedev-Sponheuer-Karnik scale), which measures earthquake intensity. Zone 4 areas can experience MSK-8 intensity, making them vulnerable to structural damage.
• In the last five years, Delhi and its surrounding regions have recorded multiple small earthquakes (magnitude 2-3), mostly unnoticed by residents but detected by seismometers.
• Such low-magnitude tremors are common, but stronger quakes are rare in the region.

Understanding the Aravalli-Delhi Fold Belt:

• Delhi is part of the Aravalli-Delhi Fold Belt, a geological structure that extends from southern and eastern Rajasthan to Haryana and Delhi.
• This region has undergone significant geological changes over millions of years, leading to folded rock formations.
• These geological stresses can sometimes trigger mild earthquakes.

Different from Himalayan Earthquakes:

• Unlike the Himalayan earthquakes, which are caused by the subduction of the Indian tectonic plate under the Eurasian plate, earthquakes in the Aravalli-Delhi Fold Belt occur due to pre-existing geological faults.
• Although the region was more seismically active in the past, tectonic activity has slowed down over time, making strong earthquakes less likely.

Sound During the Earthquake:

• Many Delhi residents reported hearing a peculiar sound during the earthquake.
• While earthquakes do produce sound, it is often at frequencies beyond human hearing.
• However, in some cases, large earthquakes can create audible sounds due to vibrations.
• These sounds are often mistaken for the earthquake itself but are usually caused by the shaking of buildings, objects, or underground structures.

Possibility of a Large Earthquake in Delhi:

• While historical records mention strong earthquakes affecting Delhi in the past, experts believe that a major earthquake originating in Delhi is highly unlikely. The strongest known earthquakes in Delhi’s history include:

• 1720: A powerful earthquake reported in Delhi.
• 1803: A large earthquake that supposedly damaged the Qutub Minar (later found to have originated near Srinagar-Devprayag in Uttarakhand).

• Delhi’s tectonic setup does not indicate the presence of large stress build-ups required for high-magnitude earthquakes.
• However, the city remains vulnerable to strong quakes originating in the Himalayan region, which could cause significant damage due to its dense population and high-rise buildings.

Conclusion:

• Delhi’s recent earthquake has once again highlighted the city's seismic vulnerability.
• While a large earthquake in Delhi is unlikely, the city’s location in Zone 4 means it is susceptible to moderate tremors.
• Understanding Delhi’s seismic history and geological structure is crucial for preparedness and disaster mitigation.
• Authorities and residents should remain vigilant and ensure that buildings and infrastructure are earthquake-resistant to minimize risks in case of a stronger quake in the future.