A rock slope failure occurred on August 13, 2016 from a 710 m high south facing slope in Dzongu valley, Sikkim, India. This failure was preceded by ten years of slope deformation. Since 2006, crack development was evident in satellite images of the eastern flank of the failure. Satellite data show deformation in the days prior to failure, while eyewitnesses attest that deformation and rock fall activity accelerated after the September 18, 2011 magnitude MW 6.9 earthquake, which had an epicenter ~50 km away. Reconstruction of the pre-failure surface on a post-failure DSM, indicates a failed volume of 8.7 million m3. The failure surface is roughly planar. However, one structure (100/48, dipdir/dip) cuts through the planar surface. The failure occurred late in the monsoon season, not coinciding with any registered earthquakes. Such rock slope failures are widespread in the deeply incised valleys of Sikkim: three such events have been reported here in the past 30 years and multiple deposits have been mapped.

This content is only available via PDF.
You can access this article if you purchase or spend a download.