Seismological Report on Sikkim Earthquake of 18th September 2011

Contents: 1. Introduction. 2. Geology and seismotectonics. 3. Macroseismic survey and damage assessment. 4. Main shock and after shock studies. Conclusion. References. Appendices.

From the foreword: The present bullet in series on Sikkim earthquake of 18th Sept 2011 summarizes the work carried out by Geological Survey of India. The present write up gives a quantitative account of computation of earthquake intensity assessment of stress build-up and possible occurrences of earthquake.

Sikkim is situated in a seismically high risk zone. Due to the movement of Indian plate towards north, stress has been accumulating in the region for impending large/great earthquake. A strong earthquake of M 6.0 occurred in 1980 in the Gangtok area. Recently medium earthquake of Mw 5.7 occurred on 14th Feb. 2006 about 60 km north of Gangtok city. Several seismic surveys were carried out by the Geological Survey of India in recent past.