Unlike Himalayan quakes caused by plate tectonics, this earthquake was an intra-plate event, resulting from "in situ material heterogeneity”.

• Tremors were more intense due to the epicentre (point on the Earth's surface directly above the focus of an earthquake) located within Delhi and the earthquake's shallow depth of 5 km (See box).

Earthquakes Due to In-Situ Material Heterogeneity

• Definition: It refers to seismic activity caused by the inherent variability in the physical properties of the Earth's crust. E.g., Rock type, presence of fluids in rock pores, etc.
• Formation: Variations in physical properties (heterogeneities) can cause stress concentration, which eventually increase the likelihood of earthquakes. 
• Influence on Faults: ‘In-situ heterogeneity’ creates stress buildup in fault zones, increasing the chances of earthquakes.
  • Delhi is placed in seismic zone IV in the seismic zoning map of India, the second highest in the country.

Why is Delhi Earthquake Prone?

• Delhi is near the Indian-Eurasian Plate collision zone, with the Indian Plate moving northward at 5 cm/year, creating stress along fault lines.
• Fault Systems: Delhi-Haridwar Ridge is an extension of the Indian Plate; Aravalli Fault System is a deep-seated geological structure, both contributing to intra-plate tremors.
• Indo-Gangetic Plain: Delhi-NCR sits on soft alluvial soil, amplifying seismic waves.