National Global Positioning System (GPS) Programme for Earthquake Hazard Assessment- An overview Manoranjan Mohanty and Dr. G.D.Gupta Seismology Division, Department of Science and Technology New Delhi-110016 . E-mail:- mohantym@alpha.nic.in Abstract Department of Science and Technology has launched a National Programme on Global Positioning System (GPS) and other geodetic studies for monitoring the crustal deformation due to earthquake occurrence and other geodynamic phenomena, on the recommendations of an Expert Group set up for the purpose. The Group recommended that an extensive GPS control network consisting of permanent stations, semi-permanent stations and field stations should be established. Further, it has been recommended that a consortium approach, involving all the organizations that are active in this field, should be adopted. Already, 18 Permanent GPS Stations all over India have been established and initiative is being taken to establish more permanent stations in the NW and NE part of Himalaya. A no of semi-permanent stations have also been established in the peninsular India region by Survey of India and Indian Institute of Geomagnetism and in the North Western Himalayan region by Wadia Institute of Himalayan Geology, in project mode. A number of projects have already been funded to SOI, WIHG (Dehradun), IIG (Mumbai), IIT (Mumbai), Tezpur University, CMMACS (Bangalore), NGRI (Hyderabad), Manipur University, Cochin University, GB Pant Institute (Almorah), CESS (Trivandrum), etc., for studying the crustal deformation process in consortium mode. Some significant results related to the movement of Indian Plate and velocity vectors have been obtained. A National GPS Data Centre has been established at Survey of India, Dehradun, where all the data of Permanent stations are being stored and analyzed. DST is also continuously supporting training programmes at different places of India in order to train the scientists in GPS technology. In addition to the above, recently DST has supported a major project to determine transformation parameters between Everest Spheroid and WGS-84 and vice versa, the final values of the transformation parameters are expected soon. Efforts are also being made to strengthen the programme by creating manpower in this technology. Introduction Scientists are using different techniques to understand the earth geodynamic processes and to monitor seismic activities in India. The geodetic and geophysical methods have been accepted as one of the most accurate and reliable techniques to understand the earthquake mechanism. After the removal of Selective Availability of satellite data by US Department of Defense, the Global Positioning System (GPS) technology is being used extensively all over the world to generate useful data for different purposes. The Department of Science and Technology has evolved a programme on National GPS to study crustal deformation processes with the following objectives:
After the 1993 Latur Earthquake, with the World Bank assisted DST project on seismic instrumentation in the Indian Peninsular Shield, geodetic and geophysical studies including GPS surveys have also been undertaken by Survey of India and other organization in the Peninsular Shield. The Department of Science and Technology, Government of India had set up an expert group on Global Positioning System observations and geodetic studies with special reference to Himalayas during July 1997 to evolve a national program on GPS and other geodetic studies for monitoring the crustal deformation due to earthquake occurrences and other geodynamic phenomena. The need for urgent requirement of monitoring the seismotectonic activities and crustal deformation was identified by the Expert Group. The Expert Group had recommended that an extensive GPS control network consisting of Permanent Stations (observing continuously), Semi Permanent Stations (to be observed for 3-5 days at least once in a year) and field stations (for local investigations) might be established in phased manner. In addition to the above, the committee had also recommended for establishment of a GPS data centre at Survey of India for storage and dissemination of GPS data and organization of specialized training programmes to train the personnel. As a follow up action of the recommendations of the Expert Group, DST has launched the National GPS Programme. Participating Organisations in the Programme.
The implementation of the National GPS Programme for Earthquake Hazard Assessment, as recommended by the GPS Expert Group, has been taken up by DST, since 1998. An extensive network of permanent, semi-permanent and field GPS stations is being established by the participating organizations, and a National GPS data centre has been established. Specifications of the GPS instrumentation for this purpose have also been formulated. A Committee has been constituted for overseeing the programme. A brief report on these activities is given below: - Establishment of Permanent Stations Permanent GPS stations at Dehradun, Dharmashala, Delhi, Hanle, Leh, Bangalore, Almora, Kodaikanal, Lucknow, Itanagar, Dhanbad, Bhubneswar, Pune and Trivandrum have already been established. Recently, DST has taken an initiative for establishing permanent stations at Tezpur, Gauwahati, Aizawl, Imphal and Kohima in NE India with the help of CMMACS, Bangalore. The establishment of permanent GPS stations in NW part of Himalaya, with the help of Wadia Institute of Himalayan Geology is being taken up and setting up of permanent stations at Jabalpur and Shillong is being done by Survey of India, Dehradun. GPS receivers have also been installed at Tirunelvelli, Kolhapur, Nagpur and Allahabad and data are being collected by Indian Institute of Geomagnetism, Mumbai. DST is also planning to establish permanent stations at Bhopal, Gangtok, Bomdilla, Visakhapatnam, PortBlair and Pondicherry. National GPS Data Center Considering the importance of management of a huge volume of GPS data collected from different GPS-related projects, the Expert Group had recommended the establishment of a National GPS data centre at SOI, Dehradun. Subsequently, a National GPS Data Centre has been set up at Survey of India, Dehradun. Achieving of GPS data is being done from the permanent GPS stations of Almora, Lucknow, Kodaikanal, Trivandrum, Pune, Bhubneswar, Leh and Hanle, and data from other stations will be added subsequently. SOI is also planning to make the data available to all authorized users through ftp/internet, so as to reduce response time for data delivery and eliminate avoidable manpower costs. Transformation Parameters The reference frame for GPS is World Geodetic System-1984 (WGS-84). GPS measurement at terrestrial sites therefore give coordinates on WGS-84 Datum. This datum is different from that of the Indian Geodetic datum i.e., Everest Datum. All Survey of India Topographical maps are based on this datum. In order to make optimum use of GPS-based coordinate system, it has become essential to determine transformation parameters for conversion of coordination of points from WGS-84 Datum to Everest Datum, and vice versa. In view of the importance of this task, DST has recently sanctioned a project entitled “Determination of Transformation Parameters between Everest Datum and World Geodetic System-1984 (WGS-84 Datum)” to Survey of India. The Survey of India has already completed GPS measurements at 272 old GT stations for this purpose. The processing of already collected data is in progress. The final values of transformation parameters are expected soon. Campaign mode studies All the participating organizations as mentioned above are deeply involved in carrying out the GPS aided crustal deformation studies in different parts of India as per the following: - Peninsular Shield campaign GPS related activities have been carried out by the Survey of India, mainly for densification of the Geodetic control in various parts of the country since 1991. GPS studies in the context of earthquake monitoring were taken up during 1994, after the 1993 Latur earthquake and continued in the World Bank Assisted DST projects in Peninsular India. One epoch of GPS observation has been completed and some significant deformation results have been obtained in Khandwa, Bhopal, Jabalpur and Yavatma areas by Survey of India. Two GPS networks have been set up by IIT, Mumbai for carrying out the deformation studies in the Koyna dam and Bhuj area. The analysis of data is being carried out using Bernese software. The changes in coordinates and baseline lengths have been calculated. Many GPS campaigns have been undertaken in western Maharashtra, Marbad region and Bhuj region by IIG, Mumbai. The data have been analyzed using GAMIT/GLOBE software. The average velocity and strain field of the above mentioned regions have already been obtained. GPS observations are being carried out for studying crustal movements in and around Palaghat Gap Shear Zone by CESS, Trivandrum. GPS observations have already been carried out on four GPS stations and baselines have tentatively been obtained. The detailed analysis of data using bernese software is under progress. North Western Himalayan Campaign 50 Campaign mode GPS stations covering the entire Himachal Pradesh, Garhwal region and parts of Ladakh, Punjab and adjoining region have been established by Wadia Institute of Himalayan Geology, Dehradun. Results from repeat measurements of the GPS stations in NW Himalaya have revealed some important conclusions about the strain accumulation and plate velocities. GPS and leveling measurements are also being carried out across parallel transects in Ladakh Himalayas by WIHG, Dehradun under another project. Other Campaign C-MMACS, Bangalore has also covered several areas through GPS campaigns, which include Southern Peninsula, Garhwal, Kumaon, Ladakh Himalayas and Gujarat. GPS measurements were also carried out in Bidar, Andamans, Shillong and Darjeeling by CMMACS, Bangalore. In addition to the above, the following new projects have been recently sanctioned by DST for carrying out campaign mode studies.
Considering the future need of suitable manpower in GPS technology, necessary the Seismology Division of DST for organizing short-term courses is making efforts, workshops and training programmes. As a result of this, 4 training programmes/short term courses have already been organized at WIHG Dehradun, IIT Bombay, Itanagar and CMMACS, Bangalore in which nearly 80 persons from various Universities and research institute have been trained. A short-term course on GPS technology and its applications is being organized at IIT Bombay during November 2002. Conclusion The number of groups working under this programme is limited and as such there is a need for involvement of new groups. This requires a regular dialogue with other geoscientific agencies and researchers in research institutions and universities. Efforts in building up expertise in GPS technology is highly essential and DST is trying to generate manpower in this new technology through training programmes and contact courses. Acknowledgements Authors are thankful to all the participating organizations who are actively involved in DST projects for providing required information in respect of their projects. | ||
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