UTC time | 1991-10-19 21:23:14 |
---|---|
ISC event | 317038 |
USGS-ANSS | ComCat |
Local date | 20 October 1991 |
Local time | 02:53 Indian Standard Time (UTC+5:30) |
Duration | ~ 45 seconds [1] |
Magnitude | 6.8 Mw [2] |
Depth | 11.6 km (7 mi) [2] |
Epicenter | 30°45′N78°49′E / 30.75°N 78.82°E [2] |
Type | Reverse [3] |
Areas affected | Uttar Pradesh India |
Total damage | $60 million [4] |
Max. intensity | MMI IX (Violent) [5] |
Peak acceleration | 0.31 g [5] |
Casualties | 768–2,000 dead [3] 1,383–1,800 injured [3] |
The 1991 Uttarkashi earthquake (also known as the Garhwal earthquake) occurred at 02:53:16 Indian Standard Time (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 and Gharwal regions of the Indian state of Uttarakhand (then still part of Uttar Pradesh). High intensity shaking resulted in the deaths of at least 768 people and the destruction of thousands of homes.
The Garhwal division in northern India, flanked by the Tons River to the west and the Alaknanda River to the east, is located at the boundary of the Indian and Eurasian tectonic plates. In the region, the Indian plate is moving northeastward at a rate of 5 centimeters (2.0 in) 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 events showed low-angle thrust faulting with varying amounts of strike-slip movement. [6]
Six three-axis accelerometers that were within 60 km (37 mi) 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, with maximum slip (1.5 m (4 ft 11 in)) 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. [7]
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 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. [4] [8]
The United States' National Geophysical Data Center and the Belgian Centre for Research on the Epidemiology of Disasters' EM-DAT database both list 1,500 fatalities for the event with EM-DAT also listing 1,383 injuries. The USGS's Preliminary Determination of Epicenters and the Utsu catalog both list 2,000 deaths and 1,800 injured. [3]
Jain et al. 1992 stated that the shock was generally moderate while further clarifying the intensities that were observed at specific locations. Ghansyali, Gongotri, and Tehri were listed as experiencing intensity VII (Very strong) shaking and Bhatwari, Budhakedar, Krishanpur, Mahinanda, Maneri, and Uttarkashi were listed as experiencing intensity VIII (Severe) shaking. In a report that documented the study of strong motion recordings of the event, Jain & Das 1993 clarified that while Bhatwari and Uttarkashi experienced intensity VIII shaking at distances of 25 km (16 mi) and 40 km (25 mi) respectively, there was a small 20 km square mile area that experienced a maximum intensity of IX (Violent). [5] [8]
Megathrust earthquakes occur at convergent plate boundaries, where one tectonic plate is forced underneath another. The earthquakes are caused by slip along the thrust fault that forms the contact between the two plates. These interplate earthquakes are the planet's most powerful, with moment magnitudes (Mw) that can exceed 9.0. Since 1900, all earthquakes of magnitude 9.0 or greater have been megathrust earthquakes.
The 1950 Assam–Tibet earthquake, also known as the Assam earthquake, occurred on 15 August and had a moment magnitude of 8.7. The epicentre was located in the Mishmi Hills. It is the strongest earthquake ever recorded on land.
The geology of Nepal is dominated by the Himalaya, the highest, youngest and a very highly active mountain range. Himalaya is a type locality for the study of on-going continent-continent collision tectonics. The Himalayan arc extends about 2,400 km (1,500 mi) from Nanga Parbat by the Indus River in northern Pakistan eastward to Namche Barwa by the gorge of the Tsangpo-Brahmaputra in eastern Tibet. About 800 km (500 mi) of this extent is in Nepal; the remainder includes Bhutan and parts of Pakistan, India, and China.
The 1999 Chamoli earthquake occurred on 29 March in the Chamoli district in the Indian state of Uttar Pradesh. Approximately 103 people died in the earthquake.
The 1905 Kangra earthquake occurred in the Kangra Valley and the Kangra region of the Punjab Province in India on 4 April 1905. The earthquake measured 7.8 on the surface-wave magnitude scale and killed more than 20,000 people. Apart from this, most buildings in the towns of Kangra, Mcleodganj and Dharamshala were destroyed. The earthquake also had a widespread impact in Jammu and Kashmir particularly in the densely populated Kashmir valley. A total of 7,000 to 8,000 people were killed in Jammu and Kashmir with 4,000 to 5,000 deaths occurring in the Kashmir valley. Widespread structural damage was reported across Himachal Pradesh, Jammu and Kashmir and Uttrakhand.
The 1975 Kinnaur earthquake occurred in the early afternoon 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 1944 Tōnankai earthquake occurred at 13:35 local time on 7 December. It had an estimated magnitude of 8.1 on the moment magnitude scale and a maximum felt intensity of greater than 5 Shindo. It triggered a large tsunami that caused serious damage along the coast of Wakayama Prefecture and the Tōkai region. Together, the earthquake and tsunami caused 3,358 casualties.
The Sagaing Fault is a major fault in Myanmar, a mainly continental right-lateral transform fault between the Indian Plate and Sunda Plate. It links the divergent boundary in the Andaman Sea with the zone of active continental collision along the Himalayan front. It passes through the populated cities of Mandalay, Yamethin, Pyinmana, the capital Naypyidaw, Toungoo and Pegu before dropping off into the Gulf of Martaban, running for a total length of over 1200 kilometers.
The 1762 Arakan earthquake occurred at about 17:00 local time on 2 April, with an epicentre somewhere along the coast from Chittagong to Arakan in modern Myanmar. It had an estimated moment magnitude between 8.5 and 8.8 and a maximum estimated intensity of XI (Extreme). It triggered a local tsunami in the Bay of Bengal and caused at least 200 deaths. The earthquake was associated with major areas of both uplift and subsidence. It is also associated with a change in course of the Brahmaputra River to from east of Dhaka to 150 kilometres (93 mi) to the west via the Jamuna River.
The 1956 Anjar earthquake occurred at 15:32 UTC on 21 July, causing maximum damage in town of Anjar in Kutch, Gujarat, India. It had an estimated magnitude of 6.1 on the surface wave magnitude scale and a maximum perceived intensity of IX on the Mercalli intensity scale.
The Main Himalayan Thrust (MHT) is a décollement under the Himalaya Range. This thrust fault follows a NW-SE strike, reminiscent of an arc, and gently dips about 10 degrees towards the north, beneath the region. It is the largest active continental megathrust fault in the world.
The Main Frontal Thrust (MFT), also known as the Himalayan Frontal Thrust (HFT), is a geological fault in the Himalayas that defines the boundary between the Himalayan foothills and Indo-Gangetic Plain. The fault is well expressed on the surface thus could be seen via satellite imagery. It is the youngest and southernmost thrust structure in the Himalaya deformation front. It is a splay branch of the Main Himalayan Thrust (MHT) as the root décollement.
The 1889 Chilik earthquake occurred on July 11 on the Gregorian calendar, or June 30 on the Julian calendar at 15:14 local time in the Tien Shan mountains. The earthquake measured an estimated Mw 7.9–8.0 on the moment magnitude scale and was assigned a maximum intensity of X (Devastating) on the MSK 64 and Rossi-Forel scales. Over 92 people across Kazakhstan, Kyrgyzstan and China were killed.
The 1885 Kashmir earthquake, also known as the Baramulla earthquake occurred on 30 May in Srinagar. It had an estimated moment magnitude of Mw 6.3–6.8 and maximum Medvedev–Sponheuer–Karnik scale intensity of VIII (Damaging). At least 3,081 people died and severe damage resulted.
The 1803 Garhwal earthquake occurred in the early morning of September 1 at 01:30 local time. The estimated 7.8-magnitude-earthquake had an epicenter in the Garhwal Himalaya near Uttarkashi, British India. Major damage occurred in the Himalaya and Indo-Gangetic Plain, with the loss of between 200 and 300 lives. It is among the largest Himalaya earthquakes of the 19th-century, caused by thrust faulting.
The 1887 Verny earthquake occurred on June 8 at 04:35 local time in the Turkestan region of present-day Kazakhstan. It had an epicenter in the northern foothills of the Trans-Ili Alatau mountain range, or just south of the city of Verny,. This earthquake destroyed the city of Verny, killing at least 330 people. A moment magnitude of 7.3–7.7 and MSK 64 intensity of X (Devastating) has been estimated for the earthquake.
The 1980 Nepal earthquake devastated the Nepal–India border region on the evening of July 29. The epicenter of the 6.6 Mw earthquake was located in Nepal, northwest of Khaptad National Park. At least 200 people died and 5,600 were injured in the disaster. Extensive damage occurred on both sides of the border, amounting to 245 million USD.
The region of Ningxia was struck by a major earthquake on the morning of 14 October 1709. It had an estimated magnitude of 7.5 Ms and a maximum felt intensity of X (extreme) on the Modified Mercalli intensity scale. The city of Zhongwei was badly damaged, including a section of the Great Wall. A total of 2,032 people were killed.
The 1858 Prome earthquake occurred on August 24 at 15:38 local time in British Burma. The earthquake occurred with a magnitude of 7.6–8.3 on the moment magnitude scale. It had an epicenter in near the city of Pyay (Prome), Bago. The shock was felt with a maximum Modified Mercalli intensity of XI (Extreme) for about one minute. Severe damage was reported in Bago, and off the coast of Rakhine, an island sunk.
The 1940 Shakotan earthquake occurred on August 2 at 00:08:22 JST with a moment magnitude (Mw ) of 7.5 and maximum JMA seismic intensity of Shindo 4. The shock had an epicenter off the coast of Hokkaido, Japan. Damage from the shock was comparatively light, but the accomanying tsunami was destructive. The tsunami caused 10 deaths and 24 injuries on Hokkaido, and destroyed homes and boats across the Sea of Japan. The highest tsunami waves were recorded at the coast of Russia while along the coast of Hokkaido, waves were about 2 m.