P. Solomon Raju

Seismicity studies in eastern Dharwar craton and neighbouring tectonic regions

Various developmental activities like installation of hydroelectric projects, multipurpose projects, nuclear power plants, rapid urbanization and industrial growth needs mapping seismically active faults and correlating with the regional tectonics. This is the present day demand from the society to seismologists at large. To meet this demand the agencies involved in earthquake research, National Geophysical Research Institute (NGRI), recently commissioned state of art broad band seismological networks in Andhra Pradesh and adjoining states in southern peninsular shield to study the seismic activity in eastern Dharwar craton. Installation of seismic networks namely Andhra Pradesh seismic network, Koyna seismic network, and shield seismic networks operated by National Geophysical Research Institute in southern peninsular shield tremendously improved the capabilities of monitoring the earthquake activity in near real time. This article deals with the application and necessity of monitoring micro earthquake activity by installing network of seismic stations along pre existing zones of weakness, which have been earlier subjected to major earthquakes like Kinnerasani-Godavari fault (Bhadrachalam region), Gundlakamma river fault (Ongole region) and characterizing the nature of faulting associated with the above.

The ISLANDS Network in the Andaman–Nicobar Subduction Zone

### Tectonics The Andaman–Nicobar Islands form the central part of the 5,000-km-long Burma–Sunda–Java subduction complex. The islands, situated to the southwest of the Indian subcontinent, currently overlie one of the most seismically active regions of the world. The complexity of this active tectonic region can be attributed to several factors, including oblique subduction, arc volcanism, and the ill-defined Andaman spreading ridge in the Andaman Sea. The oceanic lithosphere of the Indian plate subducts eastward below the oceanic part of the Burmese plate in southeast Asia (Curray et al. , 1979) identified by the Andaman–Sumatra trench and accretionary subduction complex ridges to the west of the Andaman Islands. The Andaman Sea, lying east of these islands, is a pull-apart basin rather than a typical backarc basin (Curray, 1989). The region comprises the West Andaman fault (WAF), the Sumatra fault system, and a spreading center spanning 10°–12°N in the Andaman Sea (Fig. 1). Also, the Sagaing fault, situated further east and characterized by transform faulting, demarcates the eastern boundary of the Burmese plate (Curray et al. , 1979). The central lowlands are separated from the eastern highlands of Burma by this Sagaing fault, which continues to the Andaman Sea rift zone. The young Barren and Narcondam volcanoes within the Andaman Sea, lying 150 km east of the main islands, are interpreted as a part of the inner arc. The Narcondam volcano is calm, with no historically known activity (Pal et al. , 2007). However, the Barren is designated as an active volcano that erupted in March 1991, after lying dormant for nearly two centuries and subsequently erupting in 1994–1995, 2005–2006, and 2008–2009 (Rajendran et al. , 2003; Sheth et al. , 2010). The region between the Andaman Islands and the volcanic arc is described as the foredeep sedimentary trough (Dickinson and Seely, 1979 …