Geomagnetic Investigation in the Seismoactive area of Narmada-Son Lineament, Central India

Abstract

Activation of Narmada south fault caused the devastating Jabalpur earthquake (6.0 M) on May 22, 1997. To understand the secular variation of the total geomagnetic field in the vicinity of Narmada south fault, particularly comprising the seismoactive zone of Jabalpur and its adjoining areas in the Narmada-Son Lineament, Central India, tectonomagnetic studies were undertaken by carrying repeat surveys since 2003. The repeat survey area covers a total of 70 observation stations falling in areas of Jabalpur, Mandla, Seoni, Lakhnadon and Narsimhapur in Deccan Trap provinces. Using the Proton Precession Magnetometer of sensitivity 0.1nT, simultaneous measurements of total geomagnetic field were made at all stations and at base station and the process was repeated at yearly intervals. In this study, Seismic Observatory, Jabalpur was used as reference base station. For data interpretation purpose, five magnetic profiles were drawn i.e. the Katangi-Mandla (AA'), Mandla-Lakhnadon (BB'), Lakhnadon-Narsimhapur (CC'), Narsimhapur-Jabalpur (DD') and JabalpurSeoni (EE'). Repeated yearly surveys of 2003, 2004, 2005, 2006 and 2007 bring out secular changes in total geomagnetic fields that seem to be concentrating locally. Results of these observations have shown the anomalous geomagnetic field secular variations in a range of ± 0.06 to ± 9.54 nT at separate stations over the distinct profiles. The anomalies in secular variation of the total geomagnetic field may be related to anomalous accumulation of tectonic stresses and tensions on the fault zones and crustal blocks due to recent geodynamic processes and tectonic setting of the Narmada-Son Lineament.