Delhi lies in high risk zone of seismicity

Delhi is located in zone IV, which has fairly high seismicity where the general occurrence of earthquakes is of 5-6 magnitude, a few of magnitude 6-7 and occasionally of 7-8 magnitude 

Hyderabad: Delhites woke up to a rumbling sound and strong tremors due to an earthquake which measured at 4.0 magnitude on Ritcher Scale on Monday. The earthquake, with its epicentre near Durgabai Deshmukh College of Special Education in Dhaula Kuan in New Delhi, struck at a depth of 5 km at 5.36 am.

The termors were so strong that it shook highrise buildings, creating panic among residents, who ran outside to save their lives.

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Delhi and its surrounding areas have been experiencing either lower or milder magnitude earthquakes, almost in every 2 to 3 years. The earlier quake in the region was experienced in 2015, which was of 3.3 magnitude. Earthquakes in the range of 4 to 5 magnitude are common here. According to Delhi Disaster Management Authority, Delhi region had experienced around 25 to 30 such earthquakes in the last century.

Why quakes are so frequent in Delhi area?

Seismicity around Delhi is associated with a major geological structure, which is known as the Delhi-Haridwar Ridge. It coincides with the extension of the Aravali mountain belt beneath the alluvial plains of the Ganga basin to the northeast of Delhi towards the Himalayan mountain .

The Bureau of Indian Standards has categorised regions in India into four seismic zones – II, III, IV and V. Of these, the most seismically active area is Zone V and the least active is Zone II. Delhi is located in zone IV, which has fairly high seismicity where the general occurrence of earthquakes is of 5-6 magnitude, a few of magnitude 6-7 and occasionally of 7-8 magnitude. Delhi lies among the high-risk areas.

Earthquakes occur in North India, including the Himalayas, due to collision of the Indian plate with Eurasian plate. This is a continuous process happening for the last 50 million years. These colliding plates flex, storing energy like a spring, and when the plate’s margin finally slip to release energy, an earthquake results.

Five earthquakes of Ritcher magnitude 5.5 to 6.7 are known to have occurred in Delhi or close to it since 1720 AD.

Two major lineaments namely Delhi-Haridwar ridge and Delhi-Moradabad faults pass through the territory, both having potential of generating earthquakes of magnitude upto MSK VIII. Normal depth of 30 km may be assumed for these earthquakes.

Risk for Delhi

The city’s settlement pattern has largely overlooked its geographical location and geological features. High-rise buildings in high-risk areas have been developed without proper consideration for earthquake resistance. Unplanned settlements in Connaught Place and the trans-Yamuna area, characterised by sub-standard structures, are particularly vulnerable to severe damage, even from moderate earthquakes.

After the Chamoli earthquake in 1999, which was felt in Delhi, there were reports of cracks in high-rise buildings situated on alluvial deposits in the trans-Yamuna region.

An earthquake disaster in Delhi would carry significant economic and political consequences for the entire nation.