A magnitude 4.9 earthquake struck Chamoli in Uttarakhand at 10:23 pm on October 6, according to the National Centre for Seismology, with tremors felt in Delhi, Noida and Ghaziabad.
The reach is explained by the depth. At 13 km the quake is relatively shallow, and a shallow quake sends stronger shaking to a wider area than a deep one of the same magnitude.
The location explains the frequency. Uttarakhand lies in the Himalayan belt, one of the most seismically active regions in the world, and Delhi sits in seismic zone IV, so tremors from the Himalaya are felt in the capital from time to time.
A quake of 4.9 is light to moderate, and the first reports did not mention damage or injuries.
The reports gave slightly different times, with some saying about 10:13 pm, but the NCS post gave 22:23:13 IST.
People in Bhowali, Haldwani, Khatima, Rishikesh, Gopeshwar and Badrinath reportedly felt the shaking.
The first reports did not mention any damage or injuries.
The relatively shallow depth of 13 km means that the shaking can be felt over a wide area.
Uttarakhand lies in the Himalayan belt, which is one of the most seismically active regions in the world.
Delhi lies in seismic zone IV on India’s earthquake hazard map, and it often feels tremors from earthquakes in the Himalaya.
Magnitude is a measure of the energy released at the source, and the shaking felt at a place depends on the distance and depth as well.
A magnitude 4.9 earthquake is classed as light to moderate, and damage from such a quake is usually limited.
The National Centre for Seismology reports earthquakes in India and publishes the time, magnitude, depth and location.
ANI, Business Today and other outlets carried the NCS details on the night of October 6.
Garhwal Himalaya, Uttarakhand (representative image), Wikimedia Commons, CC BY-SA 4.0