Foundation, Concrete and Earthquake Engineering

Tectonic Cause of Magnitude 6.9 earthquake of Sikim, India 2011 September 18

A magnitude 6.9 earthquake strike sikim, india on Sunday, September 18, 2011 at 06:10:48 PM at epicenter. The location coordinates are 27.723°N, 88.064°E. The hypocenter was at 12.2 miles depth. The epicenter was 42 miles north west of Gangtok, Sikkim, India.

Felt report :

1. 20 people have been killed in total.

2. 7 people have been killed in Sikkim.

3. 5 people are reported dead in Nepal.

4. 2 persons were reportedly killed in Nalanda and Darbhanga districts of Bihar, out of which one died in a stampede. .

5. 4 persons in total were also reported dead in Kalimpong, Jalpaiguri and Siliguri in West Bengal.

6. Two Army personnel were also killed in the earthquake.

Tectonics of Earthquake:

Magnitude 6.9 earthquake of Sikim, India 2011 September 18
This 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 eventsoccurring 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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