Prepared By: Sarah Bettinger
Occupancy: Education
Year Built:
Number of stories: 6
Stories below ground: unknown
Original Code: IS:1893-1984 (also Sikkim Building Construction Regulations of 1991?)
Modification: Unknown
Year Modified:
Code of Modification:
Lateral Load System: Unknown
Other Load System:
Vertical Load System: Unknown
Other Vertical Load System:
Foundation : Unknown
Other Foundation :
Country: India
State: Sikkim
City: Chungthang
Latitude: 27.60434
Longitude: 88.646597

Moonlight School

Earthquake Information



Earthquake Date 40804
Moment Magnitude 6.9
Epicentral Distance 60
Local Intensity VI Other
Site Description
PGA Lateral 0.25 (g)
PGA Vertical None (g)
Ground motion recording stations Earthquake motions were recorded at Gangtok and Siliguri by strong motion accelerographs operated by DEQ, IIT Roorkee. The PGA values recorded at these locations are 0.15g and 0.20g, respectively (Rai, 2012).
Distance to station None
Station Latitude None
Station Longitude None
Ground Motion Summary The US Geological Survey (USGS) indicates that the earthquake was located at 27.723N, 88.064E with a focal depth of 19.7km, in the India-Nepal border region. The quake occurred at the boundary between the India and Eurasian plates, in a region known for seismic activity between the Main Boundary Thrust (MBT) and the Main Central Thrust (MCT).


Damage Information



Performance summary

The building remained standing, but was severely damaged.

Damage state description

The building suffered a pancake collapse of the third story, and shortening of the fourth story.

Summary of causes of damage

1. Building suffered pancake collapse of intermediate story, as well as shortening of story above collapsed story. 2. Severe cracking and out-of-plane collapse of masonry infill panels on shortened story. 3. Reported that the shallow rock below the building foundation uplifted during ground motion.

Observed Design and Construction Characteristics


Construction Quality

MaterialsNotesContribution to Damage
Concrete Poor quality concrete is typical for construction in this area.
Reinforcing steel Smooth bars are typical for construction in this area.

ExecutionNotesContribution to Damage
Conveyance/placement of concrete
Field variance with design documents
OtherNotesContribution to Damage
Other Factors Construction Quality


Plan IrregularitiesNotesContribution to Damage
Perimeter boundary
Out-of-plane offsets in lateral resisting system
Non-orthogonal systems

Vertical IrregularitiesNotesContribution to Damage
Soft story Pancake collapse of intermediate story, partial collapse of story above collapsed story.
Weak story
Geometric variablility of lateral resisting system
In-plane discontinuity of lateral resisting system
Mass distribution
Change in stiffness

OtherNotesContribution to Damage
Other Factors Configuration

Lateral Load Resisting System‐General

StrengthNotesContribution to Damage
Overall lack of strength

StiffnessNotesContribution to Damage
Extreme Flexibility

Load PathNotesContribution to Damage
Anchorage of nonstructural elements
Out-of-plane capacity of walls
Diaphragm chords
Diaphragm openings

OtherNotesContribution to Damage
Other Factors Lateral Load Resisting System-General

Lateral Load Resisting System‐Frames

ColumnsNotesContribution to Damage
Shear strength
Flexural strength
Axial load ratio
Vertical load columns drift capacity
Interference of frame action by infill

BeamsNotesContribution to Damage
Strength relative to columns
Shear controlled behavior
Continuity of longitudinal reinforcing
Loss of vertical capacity
Interference of frame action by infill beams

JointsNotesContribution to Damage

OtherNotesContribution to Damage
Other Factors Lateral Load Resisting System-Frames

Lateral Load Resisting System‐Shear Walls

ShearNotesContribution to Damage
Diagonal tension/compression
Sliding Shear

FlexureNotesContribution to Damage
Compression zone buckling capacity
Discontinuity of wall
Boundary reinforcing fracture/buckling
Boundary Reinforcing at openings

OtherNotesContribution to Damage
Other Factors Lateral Load Resisting System-Shear Walls

Lateral Load Resisting System‐Infills

InfillsNotesContribution to Damage
Interference with frame action
Out of plane Out-of-plane collapse of masonry infill panels on floor above pancake collapse.
Attachment to framing

OtherNotesContribution to Damage
Other Factors Lateral Load Resisting Systems-Infills

Lateral Load Resisting System‐Other

FoundationsNotesContribution to Damage
Surface Rupture

OtherNotesContribution to Damage
Pile/Pier tension capacity

MiscellaneousNotesContribution to Damage
Spread footing capacity
Other Factors Lateral Load Resisting Systems-Other-Foundations Boulder below building foundation was uplifted.

OtherNotesContribution to Damage
Other Factors Lateral Load Resisting Systems-Other-Misc

Repair and Retrofit Information


Type of Retrofit or Repair


Other Retrofit or Repair

Performance Level


Hazard Level


Retrofit or Repair Code


Other Retrofit or Repair Code

Lateral Analysis


Other Lateral Analysis

Design Strategy

Retrofit Summary

Murty, C.V.R. and Sheth, A., ed. The Mw 6.9 Sikkim-Nepal Border Earthquake of September 18, 2011. Learning from Earthquakes. EERI Special Earthquake- February 2012.
Sheth, A. and Murty, C. V. R., "Concrete Coalition Project Earthquake Damage Examples from India." Earthquake Engineering Research Institute. Oakland, California. 25 June 2012.
National Information Center on Earthquake Engineering, 2011. 2011 Sikkim Earthquake: Effects on Built Environment & a Perspective on Growing Seismic Risk, (July 10, 2012).
Rai, D. C., et. al., 25 May 2012. The M 6.9 Sikkim (India-Nepal Border) earthquake of 18 September 2011, Current Science , vol. 102, no. 10, 1437-1446 .
Bhalla, N.. "Sikkim earthquake by ActionAid." SIKKIM e.newsletter. S. K. Sarda. 30 September 2011. 12 July 2012 <>.
United States Geological Survey (USGS), 2012.Magnitude 6.9- India-Nepal Border Region (25 July 2012).