GEOTECHNICAL IMPACTS OF EARTHQUAKE-RELATED MASS MOVEMENTS: SOME LESSONS LEARNT FROM THE 2011 SIKKIM EARTHQUAKE
Debasis ROY Professor Department of Civil Engineering, IIT Kharagpur, WB 721302 debasis@civil.iitkgp.ernet.in
Alpa SHETH Managing Director VMS Consultants Private Limited, Mumbai 400021 alpa_sheth@vakilmehtasheth.com
Nagendra KOLA PhD Research Scholar IIT Kharagpur, WB 721302, INDIA kola_nagendra@yahoo.in
Debasis Roy, a 1985 B. Tech (Honors) from BHU, has an MS degree from University of Idaho (1992), USA and a PhD from the University of British Columbia, Canada (1997). He practiced as a Professional Engineer in India and Canada for over ten years mainly in projects on seismic hazard and risk and geotechnical earthquake engineering before joining IIT Kharagpur in 2002.
Alpa Sheth is the Managing Director of VMS Consultants Pvt. Ltd, a structural engineering practice in Mumbai. She is a Visiting Professor at Kamla Raheja Vidyanidhi Institute of Architecture and INAE Visiting Professor at IIT Madras. She has been a Seismic Advisor to Gujarat State Disaster Management Authority for many years and is on several Code Committees of the Bureau of Indian Standards. She holds a Master of Engineering from University of California, Berkeley.
Nagendra Kola received his Bachelor’s degree in Civil Engineering in 2011 form VR Siddhartha Engineering College, Vijayawada and Master’s degree in Geotechnical Engineering from NIT Rourkela in 2014. Presently he is a Research Scholar at IIT Kharagpur.
Abstract A magnitude (Mw) 6.9 earthquake of September 18, 2011, cantered in the Sikkim-Nepal border area, affected large portions of Sikkim, West Bengal states of India and adjoining Nepal, Bhutan, China and Bangladesh. Thin population density and absence of infrastructure facilities in the epicentral region, existence of few recording instruments within the affected area and a wide variation in the ground motion parameters because of topographic effects made precise engineering assessment of the event difficult. Regardless, geotechnical impacts were largely attributable to seismically-triggered permanent ground deformations, slope movements, landslides, rock falls and over reliance on isolated shallow foundations. Many of the affected facilities were constructed on pre-existing landslide or rock 12 Volume 45
Number 1 March 2015
fall tracks or on top of steep slopes leaving them vulnerable to reactivated mass movements, seismic ground motion amplification and permanent ground deformation. This paper summarizes the lessons learnt during the aftermath of the September 18, 2011 earthquake that may lead to the development of appropriate zoning and facility development strategies in seismically active Himalayan region. Key Words : Landslides, anisotropy, slope, rock fall, reactivation, development zoning
1.
Introduction
The magnitude (Mw) 6.9 earthquake of September 18, 2011 that affected large portions of Sikkim, West Bengal states of India and adjoining Nepal, Bhutan, China and Bangladesh leading to the The Bridge and Structural Engineer