NEW DELHI: The 7.3-magnitude earthquake that hit Nepal and several parts of North India earlier in the day recorded an intensity of VIII to IX at the epicentre, while Delhi and its neighbouring areas recorded the intensity of V.
The effect of an earthquake on the earth's surface is called the intensity. The intensity scale consists of a series of certain key responses such as people awakening, movement of furniture, damage to chimneys, and finally total destruction.
"The epicentre records highest intensity. Although the magnitude was recorded at 7.3 on the Richter Scale, the intensity was recorded between VIII to IX in Nepal.
"In several parts of Indian states bordering Nepal such as the eastern part of Uttar Pradesh, Bihar, West Bengal and Sikkim recorded an intensity of VI-VII. Delhi recorded an intensity of V," J L Gautam, Head of Operations of IMD's Seismology Division, said.
Although numerous intensity scales have been developed over the last several years to evaluate the effects of earthquake, the one currently used widely in many countries is the Modified Mercalli (MM) Intensity Scale.
It was developed in 1931 by American seismologists Harry Wood and Frank Neumann. This scale, composed of increasing levels of intensity that range from imperceptible shaking to catastrophic destruction, is designated by Roman numerals.
"Intensity I is where earthquake is recorded, but people many not feel it. After intensity II, people can feel the tremor. At level V, fans or other stuff in a house may start moving or waving.
"With intensity of VI-VII, there are possible damages to any structure. Level XII means complete destruction," Gautam added.