Effects of the 2005 Muzaffarabad (Kashmir) Earthquake on Built Environment

Effects of the 2005 Muzaffarabad (Kashmir) earthquake on built environment

Studying the effects of earthquakes has widespread destruction in POK, Paki- VIII at Uri, VII at Baramulla and Kupwara long been recognized as a necessary step stan’s North-West Frontier Province and V at Srinagar on MSK scale3. How- to understand the natural hazard and its (NWFP), and western and southern parts ever, the collapse of stone walls of random risk to the society in the long term. A of the Kashmir on the Indian side of rubble types was a surprise even with rapid assessment of general damage survey LoC. This earthquake is associated with much lesser shaking. It has been well es- and documentation of initial important the known subduction zone of active tablished that the local soil site and to- observations, not only help management thrust fault along the Himalayan moun- pographical conditions play a significant of emergency response and rehabilitation tain ranges in the area where the Eurasian role in modifying the nature of ground activities, but also help to assess the need and Indian tectonic plates are colliding motion which leads to varying degree of of follow-up areas of research1,2. The and moving northward at a rate of 40 mm/yr response to similar structures. Structures Muzaffarabad earthquake of 8 October (Figure 1). located on ridges and along steep slopes 2005 which caused major devastation on The worst affected major towns on the were subjected to a greater degree of both sides of the Line of Control (LoC) Indian side of LoC are Tangadhar in Kup- damage in comparison to those located in in Kashmir, presented another opportunity wara district and Uri in Baramulla dis- valleys, during this earthquake as well. to further our understanding of earthquake trict. Significant damages have also been The affected region lies in the top two risk in the region. reported from the Poonch and Rajouri high risk seismic zones of IV and V of The Mw 7.6 earthquake on 8 October district further south from the epicentre Indian seismic code IS:1893 (ref. 4) with 2005 was a major earthquake at a depth on the Indian side of LoC. During the re- an expected intensity of IX or more in of 26 km from the surface with its epi- connaissance survey we visited places the zone V and of VIII in the zone IV. centre located at 34.493°N, 73.629°E, along National Highway NH1A during The region affected by the Muzaffara- 19 km northeast from Muzaffarabad, the 14–19 October 2005 from Srinagar to Uri bad earthquake is mountainous terrain capital town of the Pakistan Occupied and along Sopore, Durgwilla, Kupwara, where the settlement is dense in valleys Kashmir (POK) and 170 km west-north- Traigaon on the road to Tangdhar. and sparse on hill slopes. Major civil en- west of Srinagar, Jammu & Kashmir, India Damage to buildings and other struc- gineering projects in the area are high- (USGS). The event which was similar in tures in general agreed well with the in- ways, bridges, small dams and micro magnitude to the 2001 Gujarat earthquake tensity of ground shaking observed at hydro-electric projects and a few RC framed and the 1935 Quetta earthquake caused various places, with the maximum of buildings. The housing units are largely

1066 CURRENT SCIENCE, VOL. 90, NO. 8, 25 APRIL 2006 SCIENTIFIC CORRESPONDENCE low rise brick and stone masonry load mary lateral resistance against the earth- ing masonry is quite different from typi- bearing types often in association with quake forces is provided by the membrane cal brick masonry and their performance timber. The diaphragms vary from pitched action of the diaphragms (floors and in this earthquake has been once again flexible roofs to mixed flexible and rigid roofs) and bearing walls. The seismic shown to be superior with no or very lit- concrete floors and roofs. performance of load-bearing masonry tle damage. No collapse was observed in Structures need to have suitable earth- structures depends heavily on the struc- such masonry even in the areas of higher quake-resistant features to safely resist tural characteristics (strength, stiffness shaking. This timber-lacing of masonry, large lateral forces that are imposed on and ductility) of surrounding walls to resist which is locally referred as dhajji-dewari them during infrequent earthquakes. Or- in-plane and out-of-plane inertia forces (meaning patch quilt wall) has excellent dinary structures for houses are usually and of the diaphragms (floors and roofs) earthquake-resistant features. Presence of built to safely carry their own weight and to not only safely resist the shear forces timber studs, which subdivides the infill, low lateral loads caused by wind and but also to distribute the forces to verti- arrests the loss of the portion or all of therefore, perform poorly under large cal elements (walls) and maintain the in- several masonry panels and resisted pro- lateral forces caused by even moderate tegrity of the structure. gressive destruction of the rest of the size earthquakes. In Kashmir, traditional timber–brick wall (Figure 2). Moreover, the closely The majority of buildings in the affected masonry construction consists of burnt spaced studs prevent propagation of di- region use the unreinforced masonry clay bricks filled in a framework of tim- agonal shear cracks within any single walls as bearing and enclosure walls. ber to create a patchwork of masonry, panel, and reduce the possibility of out- These masonry structures can be viewed which is confined in small panels by the of-plane failure of masonry of thin half- as box-type structures in which the pri- surrounding timber elements. The result- brick walls even in higher stories and gable portion of the walls. Dhajji-dewari system is often used for walls of upper stories, especially for the gable portion of the wall, even when the walls in bot- tom stories could be made of brick or stone masonry (Figure 2 a). In older constructions, another form of timber-laced masonry, known as Taq has been practiced in which large pieces of wood have been used as horizontal run- ners embedded in the heavy masonry walls, which add to the lateral load re- sisting ability of the structure (Figure 2 b). The concept of Dhajji-dewari has also been extended to develop a mixed construction in which stones are used as filler hard material in wall panels created by a series of piers in softer coursed brick masonry of greater integrity under lateral loads (Figure 2 c). The masonry walls with stones confined in such a manner have performed quite satisfactorily, in contrast to usual brick or stone masonry. In the upper reaches of North Kashmir Himalayas, majority of houses use stone masonry in mud mortar for walls and flexible diaphragms for floors and roofs consisting of timber. Stone masonry is produced from a wide range of materials and constructed in many different forms that have shown varying degree of performance in this earthquake. Unreinforced stone masonry is very durable even in the hostile environment and can accommo- date movements and resist natural forces without becoming unstable and falling apart, especially when they are laid in even courses after proper dressing (Fig- ure 3).

Figure 1. Location of epicentre of the earthquake and its aftershocks, Main Central Thrust However, some forms of stone masonry, fault, and the towns visited in the Indian side of Line of Control (LoC). especially Random Rubble (R/R) stone

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a b c

Figure 2. Traditional masonry for proven earthquake resistance. a, Dhajji-dewari system of timber laced masonry for confining masonry in small panels; b, Taq system of embedding timber thick walls; c, Brick masonry piers for timbers in stone infilled wall.

Figure 3. Examples of mixed construction involving dhajji-dewari and dressed/undressed stone masonry and brick masonry.

a b c

Figure 4. Out-of-plane collapse of stone masonry walls.

masonry construction are extremely vul- built during the last 4 to 5 decades suf- Uri and Kupwara are a few examples. nerable to earthquakes. Undressed stones fered heavy damage especially when the Such out-of-plane failures arising from are laid in mud or cement mortar and structure is old. This was primarily due the dynamic instability of unsupported plastered in cement mortar to provide to the fact that the walls could not main- walls were also evident in collapsed tall finished surface. Most of government tain their integrity during the shaking. slender end wall in brick masonry as well. buildings, hospitals, schools, jails, etc., The collapsed walls of army buildings in Moreover, masonry walls are weakened

1068 CURRENT SCIENCE, VOL. 90, NO. 8, 25 APRIL 2006 SCIENTIFIC CORRESPONDENCE by openings for doors and windows (Fig- ings. However, there are many variants ing material. Corrugated Galvanized Iron ure 4). of pitched roofs with varying degree of (CGI) sheets have also been used as a Deficiencies of stone masonry walls seismic performance. In rural areas and roofing material in many cheaply built were more evident in R/R type masonry low cost houses, roofs are either com- school buildings. These roofs are inher- and were responsible for the majority of posed of wooden joists and planks or ently weak in shear and cannot tie the the observed damage in the earthquake- simple wooden trusses and rafters. In walls together even when they are prop- affected areas. Such deficiencies can government buildings, wooden planks erly connected to them. Most of roof render typical brick masonry buildings are placed on rafters to support the roof- failures can be attributed to a combination vulnerable to damage as shown in Figure of deficiencies such as loss of support of 5. However, timber-laced masonry can roof trusses and rafters due to failure of maintain its integrity even when the sup- masonry walls and failure of roof truss porting masonry walls in lower stories itself due to failure of joints and/or are severely damaged (Figure 6). members forming the truss or other roof Pitched roofs have been the most popu- supporting structure (Figure 7). lar choice as a roofing system for build- The area has a number of highways and pedestrian bridges over rivers, rivulets, and gorges. No serious damage to any of the highway bridges was noticed in the a areas visited away from the epicenter. However, it has been reported that the Aman Setu at India-Pak border closer to the epicenter has suffered damage. Most of pedestrian bridges were of suspension types and no particular damage to the bridge structure or to the supporting py- lons was noticed. The affected region which may experience ground shaking Figure 7. Failure of supporting walls for the roof in a traditional building using Taq system more than IX on MSK scale, has a num- of masonry at Baramulla. ber of major bridges which are simply b supported prestressed concrete girder type with inadequate seating or no provi- sion to prevent unseating (Figure 8). Roads closer to epicentral area in the mountainous region suffered extensive landslides which resulted in the closure of traffic for many days (Figure 9). The road to Tangadhar from Kupwara was not open even a week after the quake. Fissures on roads were noticed at places

which were primarily due to ground Figure 5. Damage to brick masonry build- movement across unstable slopes. Pipe- ings. a, Out-of-plane collapse of walls; b, In- lines for drinking water supply broke at plane failure of masonry walls in lower stories Figure 8. Simply supported prestressed con- several places causing severe hardships. and out-of-plane collapse at uppermost storey. An overhead water tank on shaft supported crete girder bridge on NH1A in Zone V which lacks restrainers for preventing unseating dur- staging in Traigaon suffered circumfer-

ing earthquakes. ential flexure tension and shear cracking which was empty at the time of earthquake (Figure 10). Such damages have been observed in many past earthquakes which highlight the inadequacy of current design methods of such tanks. The damage to built environment, eco- nomic loss and human casualties caused by Himalayan earthquakes are increasing rather proportionally with the growth of settlements and population in its upper reaches. Significant damage to residential, community and government buildings Figure 6. Timber-laced masonry in gable result from prevailing stone masonry wall suffered little damage whereas extensive damage in stone masonry wall rendered the Figure 9. Landslide on NH1A near Uri dis- buildings, especially those with random- building unsafe at Uri. rupted the road traffic. rubble types, which are well known for

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taken to evaluate and improve them. Similarly, seismically deficient structures need to be strengthened to reduce their vulnerability.

1. Post-Earthquake Investigation Field Guide: Learning from Earthquakes, Earthquake Engineering Research Institute, Oakland, CA, 1996, Publication No. 96-1, p. 144. 2. Reducing Earthquake Hazards: Lessons Learned from Earthquakes, Earthquake Engineering Research Institute, Oakland, CA, 1986. 3. EERI News Lett., Dec. 2005. 4. Indian Standard Criteria for Earthquake Figure 10. A 50000 gallon water tank at Traigaon developed flexure tension cracks in its sup- Resistant Design of Structures: Part 1– porting shaft rendering it unsafe for use. General Provisions and Buildings, Bureau

of Indian Standards, New Delhi, 2002, poor seismic performance. Buildings should carrying capacity. There is an urgent IS:1893 (Part 1). not only meet the functional requirements need to revive these traditional masonry of occupants but also essential require- practices which have proven their ability ACKNOWLEDGEMENTS. We thank the ments for sound earthquake-resistant de- to resist earthquake loads, in contrast to numerous officers and staff of IRCON Inter- sign and construction. contemporary colonial-style masonry national and Military Engineering Services Most residential units in the affected buildings. The seismic performance of (MES) in the affected area who provided help and support during the field visit. Special area relied on load-bearing masonry such masonry systems should be resear- thanks are due to Professor Sudhir K. Jain, IIT walls for seismic resistance. Much of the ched and guidelines developed for their Kanpur, for encouragement and support in damage could be attributed to inferior cost-effective implementation which can carrying out the reconnaissance studies in one construction materials, inadequate sup- optimally exploit their inherent ability to of the most difficult areas of the country. We port of the roof and roof trusses, poor resist seismic actions. thank DST for financial support. wall-to-wall connections, poor detailing Modern bridges, roads, water tanks, work, weak in-plane wall due to large etc., which have been constructed in the Received 24 October 2005; revised accepted openings, out-of-plane instability of Kashmir region without due considera- 17 February 2006 walls, lack of integrity or robustness, tion of high seismic activities of the Hi- asymmetric floor plans and ageing. Con- malayan region making such civil DURGESH C. RAI* ventional unreinforced masonry laced infrastructure extremely vulnerable for C. V. R. MURTY with timber performed satisfactorily as future earthquakes. There is an urgent expected as it arrests destructive crack- need that prevailing standard codes of Department of Civil Engineering, ing, evenly distributes the deformation practices for earthquake-resistant design Indian Institute of Technology, which adds to energy dissipation capac- and construction should be adhered to, Kanpur 208 016, India ity of the system, without jeopardizing and wherever these provisions are defi- *For correspondence. its structural integrity and vertical load cient, detailed studies should be under- e-mail: [email protected]

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