A magnitude 4.9 earthquake struck Chamoli in Uttarakhand on Tuesday night, and tremors were felt as far as Delhi-NCR. But why does this region shake so often?

The Himalayas sit where two giant pieces of the Earth’s crust meet. The Indian plate is slowly pushing into the Eurasian plate, and this collision is still raising the mountains. The pressure builds up and releases as earthquakes.

Uttarakhand falls in India’s highest earthquake risk zone, Zone V. The state has seen many quakes over the years because the rocks under it are still adjusting.

A magnitude 4.9 quake is classed as moderate. It is felt widely and can shake buildings, but it rarely damages well-built structures. Deeper or stronger quakes cause more harm.

Experts say the region will keep seeing such quakes. The best defence is quake-safe building design and knowing what to do: drop, cover and hold on, then move to open ground.