The 1991 Uttarkashi earthquake (also known as the Garhwal earthquake) occurred at 02:53:16

Indian Standard Time Indian Standard Time (IST), sometimes also called India Standard Time, is the time zone observed throughout India, with a time offset of UTC+05:30. India does not observe daylight saving time or other seasonal adjustments. In military and avi ...

( UTC+05:30) on 20 October with a moment magnitude of 6.8 and a maximum Mercalli intensity of IX (''Violent''). This thrust event was instrumentally recorded and occurred along the Main Central Thrust in the

Uttarkashi Uttarkashi, meaning Varanasi, Kashi of the north, is a town located in Uttarkashi district in Uttarakhand, India. Uttarkashi town is headquarters of the district. Uttarkashi is also known as Somya Kashi. Uttarkashi is a religious place for spir ...

and Gharwal regions of the

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

n state of

Uttarakhand Uttarakhand ( , or ; , ), also known as Uttaranchal ( ; the official name until 2007), is a state in the northern part of India. It is often referred to as the "Devbhumi" (literally 'Land of the Gods') due to its religious significance and ...

(then still part of

Uttar Pradesh Uttar Pradesh (; , 'Northern Province') is a state in northern India. With over 200 million inhabitants, it is the most populated state in India as well as the most populous country subdivision in the world. It was established in 1950 ...

). High intensity shaking resulted in the deaths of at least 768 people and the destruction of thousands of homes.

Tectonic setting

The

Garhwal division Garhwal (IPA: /ɡəɽʋːɔɭ/) is one of the two administrative divisions of the Indian state of Uttarakhand. Lying in the Himalayas, it is bounded on the north by Tibet, on the east by Kumaon, on the south by Uttar Pradesh state, and on the ...

in northern India, flanked by the

Tons River The Tons (टौंस नदी) is the largest tributary of the Yamuna. It flows through Garhwal region in Uttarakhand, touching Himachal Pradesh. The Tons thrust is named after this river. Its source lies in the high Bandarpunch mountain, ...

to the west and the

Alaknanda River The Alaknanda is a Himalayan river in the Indian state of Uttarakhand and one of the two headstreams of the Ganges, the major river of Northern India and the holy river of Hinduism. In hydrology, the Alaknanda is considered the source stream ...

to the east, is located at the boundary of the

Indian Indian or Indians may refer to: Peoples South Asia * Indian people, people of Indian nationality, or people who have an Indian ancestor ** Non-resident Indian, a citizen of India who has temporarily emigrated to another country * South Asia ...

and

Eurasian Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern Hemisphere, Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Ja ...

tectonic plates. In the region, the Indian Plate is moving northeastward at a rate of per year. The Main Central Thrust is the primary northwest-striking structure and dips to the north at 30–40°. The fault plane solutions from the parametric catalogs for the 1991 and

1999 File:1999 Events Collage.png, From left, clockwise: The funeral procession of King Hussein of Jordan in Amman; the 1999 İzmit earthquake kills over 17,000 people in Turkey; the Columbine High School massacre, one of the first major school shoot ...

events showed low-angle thrust faulting with varying amounts of strike-slip movement.

Earthquake

Six three-axis accelerometers that were within captured the event, including two units that were close to the projection of the fault at the surface. Analysis of the data recorded by these devices revealed the distribution of slip, moment release over time, and the location of the maximum slip. The mechanism of the event was typical of the thrust system of the

Himalayas The Himalayas, or Himalaya (; ; ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the planet's highest peaks, including the very highest, Mount Everest. Over 10 ...

, with maximum slip () occurring to the west and southwest of the hypocenter. Energy release began slowly and built to a crescendo four seconds after the initiation of the rupture. USGS Shakemap - 1991 Uttarkashi earthquake

USGS Shakemap - 1991 Uttarkashi earthquake

Damage

Scientists from the Indian Institute of Technology Kanpur (IITK) conducted a survey of the affected areas between 27 October and 4 November. Their work revealed that more than 300,000 people in 1,294 villages were affected by the shock. Stone masonry homes (that usually supported heavy roofs) fared badly in areas where high intensity shaking occurred. The United States'

National Geophysical Data Center The United States National Geophysical Data Center (NGDC) provided scientific stewardship, products and services for geophysical data describing the solid earth, marine, and solar-terrestrial environment, as well as earth observations from spac ...

indicates that 7,500 homes were damaged and another 7,500 were destroyed while the IITK report shows that up to 42,400 houses were damaged. The United States'

and the Belgian

Centre for Research on the Epidemiology of Disasters The Centre for Research on the Epidemiology of Disasters (CRED) is a research unit of the University of Louvain (UCLouvain). It is part of the School of Public Health located on the UCLouvain Brussels Woluwe campus, in Brussels, Belgium. CRED has ...

' EM-DAT database both list 1,500 fatalities for the event with EM-DAT also listing 1,383 injuries. The USGS' Preliminary Determination of Epicenters and the Utsu catalog both list 2,000 deaths and 1,800 injured.

Intensity

stated that the shock was generally moderate while further clarifying the intensities that were observed at specific locations. Ghansyali, Gongotri, and

Tehri New Tehri is a city and a municipal board in Tehri Garhwal District in the Indian state of Uttarakhand. It is the administrative headquarters of Tehri Garhwal District. This urban municipality area has 11 wards, from Vidhi Vihar to Vishwakarma P ...

were listed as experiencing intensity VII (''Very strong'') shaking and Bhatwari, Budhakedar, Krishanpur, Mahinanda, Maneri, and

were listed as experiencing intensity VIII (''Severe'') shaking. In a report that documented the study of strong motion recordings of the event, clarified that while Bhatwari and Uttarkashi experienced intensity VIII shaking at distances of and respectively, there was a small 20 km square mile area that experienced a maximum intensity of IX (''Violent'').

References

External links

M 6.8 – Uttaranchal, India
–

United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

The Great Himalayan Earthquakes
– '' Himalayan Journal'' * {{Himalayan earthquakes Uttarkashi Earthquake, 1991

Disasters in Uttarakhand Earthquakes in India History of Uttarakhand (1947–present) October 1991 events in Asia Uttarkashi district