A powerful earthquake of magnitude 4.0 hit Delhi today and tremors were felt in many areas around the national capital. According to the National Centre for Seismology, the epicentre of the quake was at a depth of about 5 kilometres. No one was harmed during the quake, except that a loud rumbling sound was heard for a few moments in Delhi at the time of the quake. Loud rumbling sounds during earthquakes are usually caused by vibrations during shallow-focus seismic tremors. According to the US Geographical Observatory (USGS), high-frequency vibrations from shallow tremors produce a noisy sound when the ground shakes and create seismic wave motion of a short length. Seismicity in North India:- Seismicity in North India, including the Himalayas, is caused by the collision of the Indian plate and the Eurasian plate. This has been happening for the last 50 million years. These colliding plates are flexible, storing energy like a spring.
