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Evaluation of parameters controlling Earthquake Management System : An analytical approach using 3S' Technology
Crustal Deformation Studies through GPS
Throughout the world most of the earthquake activity are confined to plate margin associated with crustal deformation. Now a day’s crustal movement can be recorded with high degree precision using GPS.
Crustal deformation through GPS is one of the fast emerging area and most probably the only area where the real potential of GPS lies as far as effective earthquake prediction are concerned. GPS is now being used effectively for monitoring of crustal movement. In view of its prediction potential, Indian Meteorological Department (IMD) has planned a national GPS programme. In the long term an extensive GPS network consisting of permanent station (for continuos observation) and semi permanent station (at least for a year) and other field station are planned. Twenty-seven permanent station-covering regions from Himalayas to the south India are planned. Twelve of these are for the Northwestern Himalayas and ten stations are planned for the northeastern region of India. The continuos and repeated data recording over a fixed time interval from these stations can be of great help in preparation of crustal deformation model of Indian subcontinent. Such a model will give accurate detail about crustal movement of Indian plate. Recent advancements in the space geodetic techniques have been accepted worldwide for the understanding of crustal dynamics and earthquake mechanism.
Himalayan frontal arc of the Indian subcontinent is one of the seismically active regions of the world and shows many unique features as far as earthquakes are concerned. This region has shown evidences of frequent seismic activities starting from the first phase of Himalayan orogeny. The peninsular shield of India is not left far behind and has experienced some remarkable earthquakes. The earthquakes of Latur, Maharastra(1993), Koyna, Maharastra(1967); Jabalpur, Madhya Pradesh(1997), and Bhuj, Gujrat(2001) are some of the examples of earthquakes of peninsular shield, which have caused considerable destruction. The 1819 Rann of Kutch earthquake is one of the largest intraplate events that produced a surface scarp about 100 Km Long.
The Seismotectonic Zones in the Himalayan arc bears direct bearing with the Crustal deformational history of India. Following the breakup of the Gondwana supercontinent, India first moved southwards along with Antarctica and Australia. It then moved eastwards with Madagascar and later drifted northwards as part of the African plate before rapidly moving northward by itself to collide with Asia. Throughout most of its history subduction was taking place to the north of India.
Repeated GPS measurement at different GPS stations have revealed that out of 54 mm/yr convergence rate of Indian shield, a shortening of nearly 4mm/yr is taking place between Bangalore and Delhi, within Indian shield. Whereas there is no apparent surface contraction taking place between the northern tip of the Indian shield(Delhi) and the lesser Himalayan sites. It has been observed that a stretch of nearly 100 km between Main boundary thrust ( MBT ) and Main central thrust
( MCT ) is getting shortened with the rate of nearly 10-14mm/yr while no crustal movement was detected across any of the major Himalayan frontal thrust including MBT and MCT. Modeling of the GPS data have shown that at 50 km across the strike width of the decollement is locked, to the north of which free movement is taking place. As a result strain is developed which is likely to be released through earthquake along the northern tip of the locked fault system lying the MCT (Main central thrust ). This narrow zone is seismically highly active.
In modern time, earthquakes are studied with more authenticity, as high quality seismic and geodetic data are available globally. India has also made substantial
Progress in this field with the establishment of Broad band digital seismograph and geodetic network. Data accumulated through the seismological, geological and geodetic observations can be of great help in the delineation of the earthquakes prone areas. This will have direct impact on the hazard assessment and public safety measures.