The Gujarat (India) Seismic Network

Abstract

The 26 January 2001 ( Mw 7.7) Bhuj earthquake, in the Kachchh region of Gujarat, India, caused 13,819 deaths, U.S. $10 billion in economic losses and damaged more than 1 million houses (Gupta, Purnachandra Rao, et al. 2001, Gupta, Harinarayana, et al. 2001; Rastogi et al. 2001). The city of Bhuj and neighboring villages were most affected. The damage can be seen as far as Ahmedabad, 240 km from the epicenter, where 69 reinforced buildings collapsed (Department of Earthquake Engineering, University of Roorkee 2001). Gujarat and the adjoining region falls under all four seismic zones—V, IV, III, and II—of the seismic zoning map of India (Bureau of Indian Standards 2002), with likely earthquakes of magnitude 8, 7, 6, and 5, respectively. It is one of the most seismic-prone intracontinental regions in the world. It has experienced two large earthquakes of magnitude M w 7.8 (Johnston and Kanter 1990) and 7.7, in 1819 and 2001, respectively, and seven earthquakes of magnitude M ≥ 6.0 (Figure 1) during the past two centuries (Quittmeyer and Jacob 1979; Rastogi 2001, 2004). The intense aftershock activity of the 2001 Bhuj earthquake is still continuing. Through March 2008, 14 aftershocks with M 5.0–5.8, about 200 aftershocks with M 4.0–4.9, about 1,600 aftershocks with M 3.0–3.9, and several thousand aftershocks with M < 3 have been recorded (Mandal and Johnston 2006; Mandal 2007). Regional seismicity has also increased with M ≤ 5 earthquakes and associated foreshock-aftershock sequences. At the time of the earthquake, the Kachchh region had only one seismic observatory at Bhuj operated by the India Meteorological Department (IMD), the primary agency in the country for routinely monitoring earthquakes through its national seismological network. In the past, a few analog seismic recorders and strong-motion accelerographs have been operated by irrigation projects in …