Natural Disasters and Risk Assessment in Uttarakhand with special reference to Uttarkashi Earthquake.

Abstract

Uttarkashi lies in the main Alpine Himalayan belt, one of the most earthquake prone regions of the world. Crustal instability in this belt is ascribed to the movement of the Indian plate towords the Eurasian plate at the rate of about 50mm per year. Besides several local faults, two prominent thrusts tending northwest to southeast, from the conspicuous tectonic features. The basic aim of the present work is taken just one more step to make cities safer before the next disaster strikes. Development of a mitigation plan in more economic and effective in a long run than providing an ad-hoc relief after the disaster. The earthquake caused strong ground shaking over a large area with worst effects suffered in Uttarkashi Bhatwari region. Damage was observed in unreinforced masonry buildings as well as RC frame structures. Good construction performed much better than poor quality construction. The need for RC roof and gable bands in masonry buildings was clearly underlined by the performance of buildings at the ITBP campus at Mahidanda. There was enormous loss due to landslides and collapse of retaining walls. The failure of Gawana bridge needs to be studied. This may trigger revision of the Indian code. The earth is continually evolving and undergoing changes. From our view point at the surface of the Earth, we observe and are affected by both surface processes and the external expression of the activity occurring deep within the earth. This activity may be very slow and take place over millions of years, as in the case of a major earthquake. Much of the large scale earth movement is concentrated along faults or breaks in the earth’s crust e.g. Himalayan belt of Uttarakhand when movement occurs suddenly along a fault; energy is released in the form of an earthquake. Earthquake consists of vertical and horizontal waves like motions of the ground. The horizontal motions cause heavy destructive forces being larger than the vertical waves say 5 to 10 times greater. They may further be along any direction. Aims And Objectives Of Present Work: The basic aim of the present work is taken just one more step to make cities safer before the next disaster strikes. Development of a mitigation plan in more economic and effective in a long run than providing an ad-hoc relief after the disaster. Table :1 Districtwise House types as per MSK Classifcation Name of District No. of Houses Ares of District & houses (Per km) Number of A,B,C type houses with percentage Area under MSK Intensity KM Number of houses in Intensity Area Numbe r a type houses Number B-type houses Number of C type houses Almora 282620 5385 (52.48) A 273530 (96.78%) B 6515 (2.31%) C 2575 (0.91%) VIII 800 VII 1300 VI 3285 41986 68228 177406 40636 66033 166861 968 1573 3974 382