The M6.9 Sikkim Earthquake of 18 September 2011 caused widespread devastation in the state and adjoining areas from disrupting the road network to damaging structures of commercial, public, and religious values. This event presented another opportunity to further the understanding of earthquake risk of the affected region as well as of the North-Eastern Himalayan region, which have similar patterns of seismicity, built environment and construction practices. The general pattern of damage to structures, landslides, rockfalls, etc. was consistent with the shaking associated with this event. However, collapses of many buildings and damages to structures were disproportionate to the observed intensity of shaking, primarily due to poor compliance with seismic codes, inferior quality of raw materials and shoddy workmanship. Consequently, the seismic risk in the region is growing at an alarming pace with increasing inventory of vulnerable construction. The current event provides a preview of what is likely to happen in the event of a larger earthquake which the Himalayan region has witnessed in the past. This article discusses the construction practice in Sikkim Himalayas and their seismic performance in the recent earthquake, highlighting the vulnerability of inventories and suggests steps to mitigate the seismic risk for future events.

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This paper presents an η‐compliance method to measure the J‐Δa curve for pipes with a circumferential surface crack, using the experimentally recorded load versus the crack mouth opening displacement (CMOD) relationship. This study modifies the η method commonly practiced for standard through‐thickness fracture specimens to measure the energy release rate, J, from P‐CMOD curve for pipes with a circumferential surface crack. The non‐dimensional parameter η for the surface‐cracked pipes derives from elastic–plastic finite element analyses. The relationship between the crack size and the CMOD‐based compliance, coupled with crack profiles interpolated linearly between the fatigue crack profile and the crack profile after ductile tearing, allows determining the crack depth corresponding to the measured CMOD compliance. The measured location‐specific J‐Δa curves indicate consistency with the fracture resistance curve measured from through‐thickness fracture specimens at small crack extension levels. The difference between the fracture resistances becomes significantly larger as the crack extends beyond 0.5 mm.

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