Earthquake in Himachal Pradesh
Fragile hills of Himachal Pradesh are witnessing massive construction activities on its steep slopes. Even the fact that the state falls under seismic zone IV and V and in 1905 had witnessed a big Earthquake in Himachal Pradesh killing 20,000 people and destructing around one lakh houses has not stopped people from turning slopes into concrete jungles.
With experts not ruling out the possibility of a major earthquake in future, these structures raised on fragile slopes have now posed a big threat as they might fall like a “pack of cards”. Experts said that the majority of buildings in the state have been raised without checking the strength of the foundation, testing the stability of soil and adhering to earthquake-resistant norms and without bothering to check the structural strength. High rise buildings coming up in the state to steep slopes has now become a threat to the population.
Experts said that from earthquake angle even Delhi is not safe. So, one can easily imagine the fate of buildings located in the steep slopes on the angle between 30 to 70 degrees. Fragile slopes and weak strata on which constructions have been made would further aggravate the damage. The devastating earthquake in Nepal has now shifted focus on the vulnerability of such buildings. Himachal Pradesh falls under seismically active regions of the world and has experienced earthquakes in the past.
The region has also experienced tectonic movements which are evident from the several thrusts and faults present around the region. The major tectonic features which have earthquake potential are Main Boundary Thrust (MBT) and Main Crustal Thrust (MCT). In fact, these tectonic features are present all along the entire Himalayan tectonic belt.
Regulation of construction activities in the state
After 2001 Gujarat earthquake, the state government had taken some measures to regulate the construction activities in the state by bringing major towns under the ambit of Town and Country Planning Act, but construction activity in the majority of areas remained unchecked all these years. Be it the last Indian village of Namgia located close to China border in Kinnaur district or state capital Shimla or tourist town of Dharamshala and Mcleodganj, people have constructed houses on the steep slopes without realizing whether they would be safe during an earthquake.
Districts Kangra, Hamirpur and Mandi fall in very high vulnerable category, districts which fall in high earthquake vulnerability include Chamba, Kullu, Kinnaur and part of Kangra and Shimla, whereas the moderate and low vulnerable districts are Una, Bilaspur, Sirmour, Solan, Shimla and Lahaul-Spiti respectively. Since the 1905 Kangra earthquake, the risk of extensive damage has increased more as not only the population has grown manifold but the massive construction activity too has taken place across the state.
While making construction, the majority of the population has not followed the building norms. Seismic experts have not ruled out the possibility of an earthquake of as much as magnitude 8 to struck the Himalayan region in future as the Main Boundary Thrust (MBT) of Eurasian and Indian tectonic plate passes through Himachal Pradesh which may result in exposing heavy loss to life and property during such a disaster. According to the 2011 census of state, the urban population in the last 10 years has increased by 10.03 per cent.
Town and Country Planning Act (TCPA)
In Himachal Pradesh, the Town and Country Planning Act (TCPA) is applicable only in 34 planning areas and 34 special area development authorities catering to the population of around 10 lakh while in the rest of state people are free to make construction according to their own plans. Even in the areas where the Town and Country Planning Act is in force, people have not followed the rules strictly as there are 8281 unauthorized constructions and deviations in the buildings.
While the TCPA makes it clear that no construction could be allowed on more than 40 degrees slopes, one could see rampant construction made on the steep slopes across the state especially in the major towns of Shimla, Solan, Dharamshala, Mcleodganj, Mandi and Kullu that leaves a big question mark on the enforcement of act.
Himachal Pradesh Town and Country Planning Director Sandeep Kumar said that the department cannot check each and every building to find out whether they are earthquake resistant. “It is the responsibility of engineers issuing the structural safety report and person making the construction and architect preparing the design,” he said. He said that department now allows only frame structure construction which is earthquake resistant. A report prepared by the National Institute of Disaster Management (NIDM) said that Himalayan Frontal Thrust, the Main Boundary Thrust (MBT), the Krol, the Giri, Jutogh and Nahan thrusts are some of the tectonic features that are responsible for shaping the present geophysical deposition of the state.
The seismal vulnerability of Himachal Pradesh
The seismal vulnerability of Himachal Pradesh is primarily attributed to the northward movement of the Indian plate and to the foremost dislocation tectonic options. Besides the longitudinal tectonic feature trending parallel to the mountain chain, there square measure an oversized range of transversal fractures, faults that are accountable for the seismal activity within the mountain range region normally and Himachal Pradesh especially.
The Kinnaur earthquake of 1975 was associated with transverse Kauirik fault. In fact, about 250 earthquakes with magnitude 4 and 62 earthquakes having magnitude of 5 and above have impacted the state so far.
Situated in the western Himalayas and spread over an area of 55,673 kilometres, Himachal Pradesh is a mountainous state with elevation ranging from about 350 metres to 6,000 metres above the sea level. Whether in the high in the Himalayas or the lower regions, the majority of populations have made constructions on the hill slopes making them vulnerable to earthquake threat.
Also Read: Geography of Himachal Pradesh
Professor Sandeep Singh Department of Earth Sciences, Indian Institute of Technology (IIT) Roorkee said that unscientific land use and unplanned expansion of urban areas is also overloading and destabilising the slopes in the state especially in the urban areas. He said that overloaded slopes initially may cause only minor landslides, but at later stages, they could trigger larger landslides and become vulnerable to earthquake posing threat to buildings erected on the slopes.
A study has shown that the region of eastern Ladakh, Spiti Basin and the upper Satluj River basin record a concentration of earthquakes in a well defined NE-trending seismic zone sub-parallel to the strike of Leo-Pargil Horst and the Kaurik-Chango Fault Zone.
An earthquake cannot be predicted
It is difficult to predict earthquake but at the same time, the possibility of its occurrence cannot be ruled out. After 1905, no major earthquake has occurred in the region. Earlier, people used to build houses using the traditional hill architecture which was suitable for earthquake-prone areas with very less load on the top but now concrete structures with top-heavy has made them vulnerable to earthquakes.
The small earthquakes are continually occurring all these years in the Himalayan region. To minimize the impact of the earthquake, “factor of safety” in the construction would play an important role. People should be building their houses keeping in mind the factor of safety. Earthquake resistant structures should be built though they would cost more but would ensure safety.
In Uttarkashi earthquake of 1991, houses made of concrete collapses due to heavy load on the top. “Rooftop was made of concrete, walls were of brick and stone which could not stand the tremors.
The earthquake cannot be predicted but people should learn to live with earthquake as is being done in Japan. Awareness needs to be created among people so they could remain prepared to meet any challenge lying ahead. Sensitization is more important than creating panic.
Seismicity and Vulnerability in the Himalayas
A study conducted by Dr Vishwa BS Chandel and Professor Karanjot Kaur Brar of Department of Geography, Panjab University Chandigarh, on the “Seismicity and Vulnerability in Himalayas: the case study of Himachal Pradesh” which was published in journal “Geomatics, Natural Hazards and Risk” has revealed that promotion of infrastructure, tourism and associated building activities, hydro-power generation and allied activities have been rampant in the last 20 years.
Also Read: Best Places to Visit in Himachal in Winter
The study said that construction activity has been reckless, and it has largely ignored the hazards posed by seismicity. In such a situation, the vulnerability of the human population and associated economic losses in the event of an earthquake would be very high. Seismicity in the Himalayas is much in evidence. The historical records have shown that devastating earthquakes have been a regular feature of the entire Himalayan system.
A highly devastating earthquake of magnitude 7.8 on the Richter scale had occurred in Kangra district in 1905. It is a matter of concern that no such big earthquake has occurred in Himachal Pradesh after 1905. The population in the state is concentrated in zones of very high seismicity. Most houses under Category A: ReportA report prepared by Disaster Management Cell of Himachal Pradesh Revenue Department said that unfortunately, in spite of the probable maximum seismic intensities being high, the house types mostly fall under Category A, consisting of walls of clay mud, unbaked bricks or random rubble masonry without any earthquake resisting features.
Even the burnt-brick houses, classified as Category B, as built-in Himachal Pradesh do not have the earthquake-resisting features, namely good cement mortar seismic bands and roof typing, therefore. It said this became quite evident even in 5.7 magnitude Dharamshala earthquake of 1986.
Multi-State Earthquake Project
After realizing the lurking danger, the government of India and the National Disaster Management Authority (NDM) had launched a Multi-State Earthquake Project involving Himachal Pradesh, Punjab, Haryana and Chandigarh.
The state has not only been shaken by an earthquake occurring in its territory but also in the neighbouring areas of J&K in the North, Tibet in the East and UP hills in the South East.
80 Earthquake in Himachal Pradesh So Far
Himachal Pradesh has been shaken by more than 80 times by earthquakes having a magnitude of 4 and above on the Richter Scale as per the recorded history of earthquakes.
As per the BIS seismic zoning map five districts of the state, namely Chamba (53.2%) Hamirpur (90.9%), Kangra (98.6%), Kullu (53.1%), Mandi (97.4%) have 53 to 98.6 percent of their area liable to the severest design intensity of MSK IX or more, the remaining area of these districts being liable to the next severe intensity VIII. Two districts, Bilaspur (25.3%) and Una (37.0%) also have a substantial area in MSK IX and rest in MSK VIII. The remaining districts also are liable to intensity VIII.
Also Read: History of Himachal Pradesh
Quake revisits after 50 years
Some experts said that earthquake revisits after a gap of 50 years and in Kangra district, for the last 110 years no major Earthquake in Himachal Pradesh has occurred. A study conducted a couple of years back by National Disaster Management Authority (NDMA) had shown that during a natural disaster like earthquakes 17% of people would be injured while 3 to 4 per cent people would die. The study has also shown that an earthquake of 8 or above magnitude would kill around 1.6 lakh people out of 69 lakh population in Himachal Pradesh.
Severe Earthquake in Himachal Pradesh
Most severe earthquakes in Himachal Pradesh occurred in past:
4th April 1905: In Kangra earthquake of 7 .8 magnitude had killed 20,000 people and 53,000 domestic animals had perished while 1 lakh houses destroyed. The economic cost of recovery was estimated at 2.9 million rupees.
19th January 1975 Kinnaur: Earthquake of 6.8 magnitudes had killed 60 people while 100 others were badly injured. 2000 dwellings devastated and 2500 people rendered homeless.
26th April 1986 Dharamshala: Earthquake of 5.5 magnitudes had killed 6 people. Extensive damage to buildings. Loss estimated at 65 crores.
24th March 1995 Chamba: Earthquake of 4.9 magnitudes had leftover 70% of houses with cracks.
29th July 1997 Sundernagar: Earthquake of 5.0 magnitude had left around 1000 houses damaged.
Also Read: Best Places to Visit in Himachal in Summer
Guidelines for Constructing Earthquake-Resistant Home
Guidelines for constructing earthquake-resistant structure issued by Town and Country Planning department: House or building should be designed by a qualified Architect/ Planner/ Engineer etc. The construction should be undertaken strictly in accordance with the architectural as well as structural design. Otherwise, there is no use of consulting a professional person.
A structure should be as simple as possible. By simple it means “Symmetry of plan, mass and rigidity”. Though it’s a very difficult proposition and ideally not achievable, maximum efforts should be made to do so. Earthquake forces are enhanced when a building is comparatively taller, stiffer, heavier and unsymmetrical or illogical. Since earthquake force is a function of weight the building should be as light and small as possible. Besides, the roof, as well as upper storeys, should be kept the light. Heavier floors are planned at bottom levels only.
Due consideration should be given to the prevailing soil conditions.
Avoid planning huge structures on loose sandy soils or where a site is a water prone. In these situations, there always exists a possibility of liquefication – a position in the event of an earthquake when the soil loses strength and behaves as a fluid. There should be proper and adequate setbacks. A high rise structure adjoining an ordinary structure may also take it along with in the event of a collapse. Adequate setbacks provide a cover to the stresses and strains being returned to the mother earth in the case of an earthquake.
If buildings are all connected or joined together the situation may become chaotic. The building may include features like plinth beams, lintel band, monolithic constructions etc. One must avoid doors and windows at the corners of the buildings. There should not be too many openings. Every opening should be suitably strengthened by vertical and horizontal reinforcement.
In load-bearing structures the solid walls should be positioned symmetrically in both the directions. Moreover, these must-have vertical continuities and properly anchored to the slab.
Huge projections / chajjas should be avoided
In case they are unavoidable, they must be properly anchored with the main structure. Ceiling plaster is as light and thin as possible. The suspended ceiling should be the lightest in weight. Sloping roofs are ideal from a seismic point of view.
Length of a building may not exceed 3 times its width. Buildings having plans or shapes like L, T, E, Y etc should be separated by rectangular parts by adequate separation. In the case of RCC structures, columns should be stronger than beams, especially the end columns and the periphery columns.
The columns should preferably be symmetrical, RCC shear walls must be incorporated as an essential feature in both the directions. On record, no such building which had shear walls has ever collapsed in the event of a tremor. Non-structural parts like almirahs, shelves, parapets, water tanks should be properly tied to the structural parts of the buildings. The premises around the buildings must be developed properly.
In hill areas, slopes are developed in steps/ terraces or through retaining works. There must be an efficient system of disposal of all types of water-rain, drainage, sewage etc. No illogical or ad hoc additions – vertically as well as horizontally be made to the building once it has been completed according to structural design. All temptations for additional area or floor must be avoided.
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