Configuration of an optimum seismological network for India

Abstract

India Meteorological Department (IMD) is the nodal agency of Government of India responsible for monitoring seismicity in and around the country. IMD maintains the national seismological network consisting of 47 permanent observatories, in addition to some observatories in northern India for special studies. A 16-element VSAT-based digital telemetry system for close monitoring of seismicity in and around Delhi is also in operation. In addition to IMD, several state/central government organizations, universities and R&D institutions are also operating seismological observatories in various parts of the country. Some of these observatories in the Peninsular shield region have been upgraded in the recent past with state-of-the-art digital broadband seismograph systems, in addition to opening 10 such new digital broadband stations. This paper makes an attempt to assess the magnitude threshold of routinely detecting and locating earthquakes occurring any where in the country with the existing IMD network. Using the seismic wave attenuation characteristics in the Himalayan and Peninsular shield regions, we have estimated epicentral distance up to which a regional earthquake of given magnitude can be detected and located as well. The minimum number of observatories required for uniform azimuthal coverage and accurate determination of hypocentral parameters has also been taken into consideration. An optimum seismological network configuration has been worked out based on the above inputs. It is found from the analysis that the existing IMD network is capable of detecting and locating earthquakes of magnitude 3.5 and above occurring in the mainland of the country, except for a few pockets in Rajasthan, Gujarat, Arunanchal Pradesh and J&K. An attempt has also been made to show that regional earthquake monitoring capability would largely improve by suitably upgrading and integrating the existing seismological observatories operated by various other agencies together with setting up a number of new observatories in the instrumental gap areas.