USGS upgrades Sikkim Earthquake to 6.9; Two minor aftershocks today

National Earthquake Information Center of U.S. Geological Survey (USGS) has upgraded the largest Sikkim quake from 6.8 magnitude to a 6.9, and the other two at magnitudes 4.8 and 4.6. All three occurred within an hour and 15 minutes, the U.S. agency said. The India Meteorological Department (IMD) has held on that the largest earthquake was 6.8 magnitude, 5.7 magnitude and 5.3 magnitude.

In terms of energy, each whole number increase in the intensity of earthquake corresponds to an increase of about 31.6 times the amount of energy released. Therefore, a 7.0 earthquake on the Richter scale releases 31.623 times more energy than a 6.0 and a 8.0 on the Richter scale releases 1000 times more energy than a 7.0. A 0.1 increase in earthquake on Richter scale suggests nearly three times more powerful earthquake. Hence the difference between 6.8 and 6.9 is significant. A 6.0–6.9 Strong earthquake is destructive in areas up to about 160 kilometres (100 mi) across in populated areas.

The US agency said that the region has experienced relatively moderate seismicity in the past, with 18 earthquakes of Magnitude 5 (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.

USGS said that the depth of the earthquake was 19.7 km (12.2 miles) with an uncertainly of horizontal +/- 13.5 km (8.4 miles); vertical+/- 3.5 km (2.2 miles).

Sikkim Earthquake USGS

The IMD has said that a slight magnitude earthquake (M:3.9) also occurred at 06 hours 22 minutes IST on 19th September, 2011 in the Latur district of Maharashtra. Though the event is located about 1500 kms away from the epicenter of the earthquake in Sikkim-Nepal border region of 18th September, 2011 and hence felt not directly related to it.

The most recent powerful earthquake in the area was the Sikkim earthquake of 14.02.2006 (M: 5.7) and Bhutan earthquake of 21.09.2009 (M:6.2). The IMD has also said that the entire area of Sikkim lies in Zone IV, which is considered fairly dangerous.



  • loday rabten

    hi. thanx fr d information as i m just 150kms away from epic centre at Bhutan. we were really shocked to hv such experience in my life. Still we r in very scary to live as feeling that another after shock mAY occur at any time. so we would earnestly like to know whether will be possibility of reoccurance of such incidence at any time. plz advice for the precautionary meASURE . THANKING YOU.

  • keshav luitel

    १८ सेप्टेम्बर २०११ मा आएको भयानक भूकम्प बाट सिक्किमा भएको अपुरणीय क्षिति प्रति हामि अत्यधिक दुखि छौ विधिको विधान माथि भाला मनुस्यको के लाग्छ र सिक्किमे जनतालाई पर्न गएको यो आपत कालिन परोस्थिति मा हामि बाट जे जस्तो सहयोग हुन्छ हामी गर्न सदैव तत्पर छौ यो दैविक दुर्घटनामा परेर दिवंगत भएका सम्पूर्ण व्यक्ति प्रति गहिरो समवेदना प्रकट गर्दछौ i आचार्य ड़ा. केशव लुइँटेल श्रीमती सरिता लुइँटेल सुश्री प्रदक्षीणा लुइँटेल

  • iSikkim

    Dear Rabten and Keshav,
    We are all saddened by the quake and the innumerable tragedies it has caused. As for recurrence of earthquake, most experts have held that a repeat on a big scale is unlikely. Yet, we can’t ignore that there is no foolproof scientific procedure to determine quake. Hence, we can’t be sure. Still, we can hope that the situation is not going to worsen in terms of recurrence. Aftershocks, may be but weaker ones and harmless. Precaution, you can’t ignore though.
    With wishes and prayers for all

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