| 词条 | 1991 Uttarkashi earthquake |
| 释义 |
| name = 1991 Uttarkashi earthquake | timestamp = 1991-10-19 21:23:14 | anss-url = usp0004y1r | isc-event = 317038 | image = | alt = | caption = | map = | map_alt = | map_caption = | map2 = {{Location map+ | India |places ={{Location map~|India|lat=31.55|long=74.34|label=Lahore|position=left|label_size=120|mark=Green pog.svg}}{{Location map~|India|lat=28.61|long=77.23|label=Delhi|position=left|label_size=120|mark=Green pog.svg}}{{Location map~|India|lat=27.7|long=85.33|label=Kathmandu|position=top|label_size=120|mark=Green pog.svg}}{{Location map~|India|lat=30.75|long=78.82|mark=Bullseye1.png|marksize=40}} | width = 250 | float = right | caption = | relief =yes}} | local-date = 20 October 1991 | local-time = 02:53 | duration = ~ 45 seconds[1] | magnitude = 6.8 {{M|w|link=y}} | depth = {{convert|11.6|km|mi|0|abbr=on}} | location = {{coord|30.75|78.82|region:IN_type:event|display=inline,title}} | fault = | type = Thrust fault[5] | affected = India | damage = $60 million[6] | intensity = IX (Violent)[6] | pga = .31g[8] | tsunami = | landslide = | foreshocks = | aftershocks = | casualties = 768–2,000 dead[5] 1,383–1,800 injured[5] }} The 1991 Uttarkashi earthquake (also known as the Garhwal earthquake) occurred at {{tooltip|02:53:16 20 October local time|21:23:16 19 October UTC}} 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. Tectonic setting{{See also|Geology of the Himalaya}}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 {{convert|5|cm|sp=us}} 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.[1] EarthquakeSix three-axis accelerometers that were within {{convert|60|km|abbr=on}} 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 ({{convert|1.5|m|abbr=on}}) 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.[2] DamageScientists 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.[6][3] Intensity{{see also|Earthquake zones of India}}{{harvnb|Jain|Singh|Gupta|Nagar|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, {{harvnb|Jain|Das|1993}} clarified that while Bhatwari and Uttarkashi experienced intensity VIII shaking at distances of {{convert|25|km|abbr=on}} and {{convert|40|km|abbr=on}} respectively, there was a small 20 km square mile area that experienced a maximum intensity of IX (Violent).[4][3]See also
References1. ^{{citation|title=Himalayan hazard study on the basis of stress and strain state of 1991 Uttarkashi earthquake using Coulomb stress transfer model|first=D. K.|last=Gupta|first2=D.|last2=Bhowmick|first3=P. N. S.|last3=Roy|year=2015|journal=Geomatics, Natural Hazards, and Risk|volume=6|number=2|pages=133, 140|doi=10.1080/19475705.2013.820797}} [5][6][7]2. ^{{citation|title=Rupture history and seismotectonics of the 1991 Uttarkashi, Himalaya earthquake|url=http://www.sciencedirect.com/science/article/pii/0040195195001549|first=F.|last=Cotton|first2=M.|last2=Campillo|first3=A.|last3=Deschamps|first4=B. K.|last4=Rastogi|year=1991|journal=Tectonophysics|volume=258|issue=1–4|pages=35–51|doi=10.1016/0040-1951(95)00154-9|bibcode=1996Tectp.258...35C}} 3. ^1 {{citation|title=Garhwal Earthquake of Oct. 20, 1991|url=http://www.nicee.org/eqe-iitk/uploads/EQR_Uttarkashi.pdf|first=Sudhir. K.|last=Jain|first2=Ramesh P.|last2=Singh|first3=Vinay K.|last3=Gupta|first4=Amit|last4=Nagar|year=1992|publisher=National Information Centre of Earthquake Engineering|series=EERI Special Earthquake Report|volume=26|number=2|pages=1–3}} 4. ^1 {{citation|title=Analysis of Strong Motion Records from Uttarkashi Earthquake for Assessment of Code Provisions for Different Seismic Zones|url=http://www.iitk.ac.in/nicee/skj/Research_Papers/ANALYSIS%20OF%20STRONG%20MOTION%20RECORDS%20FROM%20UTTARKASHI_39.pdf|first=Sudhir K.|last=Jain|first2=Satrajit|last2=Das|date=1993|journal=Earthquake Spectra|volume=9|number=4|pages=739, 742|doi=10.1193/1.1585738}} 5. ^1 2 3 {{citation|title=Significant Earthquake Database|url=https://www.ngdc.noaa.gov/nndc/struts/form?t=101650&s=1&d=1|author=National Geophysical Data Center / World Data Service (NGDC/WDS)|publisher=National Geophysical Data Center, NOAA|doi=10.7289/V5TD9V7K|year=1972|type = Data Set}} 6. ^1 2 3 {{citation|title=PAGER-CAT Earthquake Catalog|url=https://earthquake.usgs.gov/static/lfs/data/pager/catalogs/|author=USGS|date=4 September 2009|publisher=United States Geological Survey|series=Version 2008_06.1}} 7. ^1 {{citation|title= Precursor seismicity, foreshocks and aftershocks of the Uttarkashi earthquake of October 20, 1991 at Garhwal Himalaya|url=http://www.sciencedirect.com/science/article/pii/S0040195197814886|first=J. R.|last=Kayal|year=2015|journal=Tectonophysics|volume=263|issue=1–3|page=339|doi=10.1016/S0040-1951(97)81488-6|bibcode=1996Tectp.263..339K}} }}Sources{{refbegin}}
External links
7 : 1991 disasters in India|1991 earthquakes|Disasters in Uttarakhand|Earthquakes in India|History of Uttarakhand (1947–present)|October 1991 events in Asia|Uttarkashi district |
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