1975 Kinnaur earthquake
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| Date | January 19, 1975 |
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| Magnitude | 6.8 Ms |
| Depth | 33 km |
| Epicenter | 32°28′N 78°26′E / 32.46°N 78.43°ECoordinates: 32°28′N 78°26′E / 32.46°N 78.43°E |
| Areas affected | India, Himachal Pradesh |
| Max. intensity | IX (Violent) |
| Casualties | 47 |
The 1975 Kinnaur earthquake occurred in the early afternoon (local time) (08:02 UTC) of 19 January. It had a magnitude of 6.8 on the surface wave magnitude scale and a maximum perceived intensity of IX (Violent) on the Mercalli intensity scale, causing extensive damage in Himachal Pradesh, in northern India. Its epicentre was in Kinnaur district in the southeastern part of Himachal Pradesh and caused 47 casualties. Landslides, rock falls and avalanches caused major damage to the Hindustan-Tibet Road. The earthquake affected many monasteries and buildings in the state and led to an extensive restoration work in the late 1970s and early 1980s in Himachal Pradesh. The Spiti and Parachu valleys in particular suffered the greatest damage being on the north-south Kaurik-Chango fault, causing damage to landmarks such as Key Monastery and Tabo Monastery.
The state of Himachal Pradesh lies towards the southern boundary of the Himalayan mountain belt, which was formed by the collision between the Indian Plate and the Eurasian Plate. The mountain building that formed the Himalayas is an example of thrust tectonics and is dominated by thrust faulting. There is however, a significant amount of extension along the length of the mountain belt, possibly related to its arcuate form, with the extension accommodating the bulging out of the frontal part of the Himalayas. However, the faulting in the NW Himalayas demonstrates west-east extension, which is at a fairly high angle to the trend of the main thrust structures and may be better explained as partly accommodating the eastward spreading of the Tibetan Plateau. One of the most significant extensional structures in Himachal Pradesh is the Kaurik-Chango Fault Zone. This is interpreted to be seismically active from the presence of thermal springs and gypsum deposits and from studies of soft-sediment deformation structures thought to be seismites. These seismites have been used to suggest eight earlier earthquakes of magnitude greater than 6 in the Sumdo area affecting these Late to Holocene sediments. The estimated recurrence interval for earthquakes along this fault zone is about 10,000 years.
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