Magnitude 6.9 - INDIA-NEPAL BORDER REGION

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2011 September 18 12:40:48 UTC

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Earthquake Details

  • This event has been reviewed by a seismologist.
Magnitude6.9
Date-Time
Location27.723°N, 88.064°E
Depth19.7 km (12.2 miles)
RegionINDIA-NEPAL BORDER REGION
Distances68 km (42 miles) NW of Gangtok, Sikkim, India
119 km (73 miles) NNW of Shiliguri, West Bengal, India
272 km (169 miles) E of KATHMANDU, Nepal
572 km (355 miles) N of Kolkata (Calcutta), West Bengal, India
Location Uncertaintyhorizontal +/- 13.5 km (8.4 miles); depth +/- 3.5 km (2.2 miles)
ParametersNST=344, Nph=348, Dmin=371.8 km, Rmss=1.21 sec, Gp= 22°,
M-type="moment" magnitude from initial P wave (tsuboi method) (Mi/Mwp), Version=C
Source
  • Magnitude: USGS NEIC (WDCS-D)
    Location: USGS NEIC (WDCS-D)
Event IDusc0005wg6
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Earthquake Summary

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Felt Reports

At least 94 people killed, several injured and 5,000 displaced and several thousand buildings and many roads and bridges destroyed or damaged in the Sikkim-Bihar-West Bengal area; 6 people killed and 25 injured and at least 4,300 buildings destroyed or damaged in Bhojpur, Ilam, Panchthar and Sankhuwasabha, Nepal; 7 people killed and 136 injured in Tibet, China; 1 person killed and 16 injured and at least 6,000 buildings damaged in the Paro-Thimphu region, Bhutan; minor damage to several buildings in Dhaka, Bangladesh. Total economic loss in India estimated at 22.3 billion US dollars. Electricity, telecommunications and water supplies disrupted and landslides and mudslides occurred in Sikkim, India, eastern Nepal and the Paro-Thimphu region, Bhutan. Felt (VII) at Gangtok and Shiliguri; (VI) at Jalpaiguri; (V) at Bandel, Baranagar, Barddhaman, Koch Bihar, Darjiling, Dispur and Guwahati; (IV) at Barakpur, Calcutta, Dhanbad, Durgapur, Haora, Iranagar, Muzaffarpur, Nagaon, Patna, Ranchi, Shillong and Tura; (III) at Delhi, Dam Dam, Faizabad, Ghaziabad, Gurgaon, Jaipur, Kharagpur, Lucknow, Noida, Rurki and Silchar; (II) at Agartala and Jamshedpur, India. Felt northwest to Chandigarh, southwest to Bhopal, south to Bhubaneshwar and east to Nahorkatiya. Felt (VI) at Damak, (V) at Biratnagar, Dhulikhel, Kathmandu and Pokhara, (IV) at Bhaktapur, Bharatpur, Patan and Tansen and (III) at Kirtipur, Nepal; (VI) at Thimphu and (V) at Paro, Bhutan; (V) at Lhasa, China; (IV) at Barguna, Chittagong, Dhaka, Rajshahi and Sylhet, Bangladesh. Felt in much of Bangladesh, Bhutan and eastern Nepal.

Tectonic Summary

The September 18, 2011 India-Nepal border region earthquake occurred near the boundary between the India and Eurasia plates, in the mountainous region of northeast India near the Nepalese boarder. Initial analyses suggest the earthquake was complex, likely a result of two events occurring close together in time at depths of approximately 20 km beneath the Earth's surface. At the latitude of the September 18 earthquake, the India plate converges with Eurasia at a rate of approximately 46 mm/yr towards the north-northeast. The broad convergence between these two plates has resulted in the uplift of the Himalayas, the world's tallest mountain range. The preliminary focal mechanism of the earthquake suggests strike slip faulting, and thus an intraplate source within the upper Eurasian plate or the underlying India plate, rather than occurring on the thrust interface plate boundary between the two.

This region has experienced relatively moderate seismicity in the past, with 18 earthquakes of M 5 or greater over the past 35 years within 100 km of the epicenter of the September 18 event. The largest of these was a M 6.1 earthquake in November of 1980, 75 km to the southeast.

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