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.
