RESILIENCE OF VERNACULAR STRUCTURES TOWARDS EARTHQUAKE

Abstract

Vernacular structures are specific to a region and reflect the traditional wisdom of constructing houses using locally available materials and basic techniques. There exist some exceptional vernacular structures which have shown outstanding resilience during earthquakes in severe seismic zones. This gives a strong reason to study these earthquake resistant vernacular structures which have been saving lives of the occupants since a commendable span of time. Five vernacular structures, found on the plate boundary regions i.e severe seismic zone, are studied for their features which have made them resilient to earthquakes. These are: Bhunga houses of Gujarat, lkra houses of Assam. Koti banal structures of Uttarakhand & Himachal, Dhajji Dewari of Kashmir and Nicobarese huts of Nicobar Islands. The intrusion of modern construction practices even in the difficult locations, where these vernacular structures mostly exists, has overlooked these traditional practices and these structures are losing their real attribute. Modern interference and modification in design - based on the experience from past earthquakes, affects the vulnerability of vernacular structures. The affect on vulnerability due to evolution in design of various building parameters is shown through an evolution-vulnerability index. In further chapters, risk assessment of the Kangra seismogenic source zone is done by applying the methodology as per Arya (2013) and districts with highest risk are studied. Parameters used in assessing seismic risk were: building types and grade of damage, housing data, seismic zoning map of India (BlS: 1893- 2002), population of each district, and time of occurrence of the earthquake. This study indicates that Kangra and Mandi district would suffer maximum human casualty in terms of numbers and percentage respectively. Few of the susceptible areas in these districts are interpreted based on the physiography and human settlements, through satellite images. These areas might suffer damage due to hazards like landslides, rockfall, liquefaction etc. Being located in the regions through which MBT passes, lot of destruction is seen in past earthquakes but still modern construction is rushing in these terrains where the earthquake resistant vernacular structures have shown resilience and survived. Thus these practices need to be revived and lessons learnt from vernacular approach both at planning or settlement level and building level can form the basis for new developments coming up in such regions. Also there is a need to preserve the existing vernacular structures so that they can be examples for more years to come and should be promoted by initiatives of authorities concerned in disaster management.