An investigative study of seismic landslide hazards

A decade ago, in September 2006, the European Commission sanctioned Amrita University, Kerala, to design, develop, and deploy a wireless sensor network-based landslide monitoring system. The deployment was completed in June 2009, at the Anthoniar Colony Landslide in Munnar, Kerala, and the system has been in successful operation since then. Recently, the Government of India commissioned Amrita University to deploy a similar landslide monitoring system in the Himalayas. We selected the Chandmari Landslide in Gangtok City, Sikkim, as our deployment site. The deployment has been phased in two stages. The first stage, completed in June 2015, was a pilot deployment in which a 33.5 m deep borehole was drilled into rock, piezometers and inclinometers were installed, and rock samples were extracted and analyzed. Soil samples were extracted from elsewhere on the hill and tested. In the second stage, we will instrument other areas of Chandmari Hill, so that the entire region can be adequately monitored. Chandmari lies in a seismically active zone and has experienced earthquake-induced landslides in the past. In this paper, we present a thorough analysis, considering linear and gridded seismicity models and three sets of ground motion prediction equations, and estimate seismic hazard at Chandmari. In addition, we report, in detail, the results of the Chandmari soil and rock tests. We then describe a method that uses these soil and rock test results and seismic hazard analyses to estimate seismic landslide hazard at the site.