GPS for Earthquake Affected Areas in Gujarat

GPS for Earthquake Affected Areas in Gujarat

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Madhav N Kulkarni

Various government agencies are applying GPS for understanding and monitoring earthquake crustal deformations and dynamics

In India, an extensive high precision Geodetic & Geophysical control network has been established by Survey of India (SOI), the National Mapping Agency of Government of India, for the primary purpose of national mapping, through dedicated efforts of over two centuries.

Application of Geodesy for Earthquake Studies in India
Recently, various national organisations and institutions, including Geological Survey of India (GSI), National Geophysical Research Institute (NGRI), Indian Institute of Geomagnetism (IIG), Indian Institute of Technology Bombay (IITB), Centre for Mathematical Modelling & Computer Simulation (CMMACS), Bangalore, etc. have taken up geodetic, geophysical and geological surveys for specific purposes. The extensive horizontal and vertical geodetic and geophysical control network established through these collaborative efforts, and the huge amount of valuable data thus generated, have contributed significantly towards monitoring the crustal dynamics of the Indian sub-continent. In the past, the geodetic studies were carried out using the conventional terrestrial techniques, mostly by SOI, which consisted of establishing a dense high precision geodetic survey control network of survey pillars, bench marks and bases, around the location of the active fault under investigation, using conventional geodetic instruments and techniques. Repeat observations over this network, carried out periodically, would provide precise estimates of the crustal deformation vectors and velocities, rotations, etc. in horizontal as well as vertical directions, between the observation epochs.

During the period from 1984 to 1992, an inter-disciplinary national programme for seismotectonic studies in the Himalayan region, involving 11 Government institutions, which was functioning under the Department of Science & Technology (DST), Government of India, has collected valuable data for such studies. After the 1993 Latur earthquake, extensive geodetic and Global Positioning System (GPS) investigations have been taken up in that region, and a comprehensive plan to extend such studies, by GPS surveys, to the Peninsular Shield of India and the Himalayan region, is also being implemented by DST. In order to evolve a ‘National Programme on GPS for Geodynamic Studies in India’, by integrating the GPS control network for Peninsular Shield, and other existing GPS stations, to cover the entire country, DST has set up a GPS Expert Group. This National GPS Network for Geodynamics, recommended by the Expert Group and now being implemented in a Project by DST, consists of permanent, semi-permanent, and many field GPS stations to be established in campaign mode, to monitor the crustal deformations. Several GPS research groups are engaged in studies of specific regions under this National programme. The GPS teams of IITB, CMMACS and IIG have now undertaken GPS studies for monitoring the post-earthquake deformations in the Gujarat area, after the Jan. 2001 earthquake.

Efforts in Progress

GPS field data collection for the Bhuj earthquake has been taken up by a team of research fellows and students of the Dept., under the guidance of Prof. M. N. Kulkarni, are carrying out GPS work in the area on priority basis, as a DST-funded project.

Work Plan:
A collaborative work, involving the GPS teams from IIT Bombay, CMMACS, CSIR, Bangalore, and GII, Mumbai, has been taken up, to carry out immediate GPS observations in the earthquake-affected area of Gujarat near Bhuj, to understand the post-earthquake crustal deformation pattern, and for monitoring crustal dynamics in this earthquake-affected region in the future. GPS teams from University of Colarado, USA, and University of Tokyo, Japan are also carrying out GPS observations in the area, and the joint work is being co-ordinated by Prof. M. N. Kulkarni. It is proposed to establish about 25-30 GPS stations in the area, and few reference stations outside the earthquake affected region. The aim of establishing these stations is to monitor the deformations of the region from a reference point outside the region, and to monitor the deformations of the region near the epicentre. These observations will be useful in estimating the crustal deformations in the region, using GPS repeat observations in the future also . The post-earthquake GPS studies and the repeat observations subsequently, is expected to yield valuable data related to this tragic earthquake.