The Narmada-Son Fault zone is a major east-west trending lineament that crosses central India for well over 1,000 kilometres, closely following the courses of the Narmada and Son rivers. It marks the boundary of an ancient rift and one of the oldest and most fundamental tectonic structures of the Indian subcontinent.
Originally formed as a set of rift-bounding normal faults deep in geological time, the Narmada-Son zone has been repeatedly reactivated, and under present-day compression its faults move mainly in a reverse sense. It separates distinct crustal blocks and controls the alignment of the Narmada valley across the Indian peninsula.
Although seismicity is moderate compared with the Himalaya, the fault zone has produced notable intraplate earthquakes, including the 1997 Jabalpur earthquake of magnitude 5.8 that caused damage and casualties in central India. Its length and deep crustal roots make it an important structure for evaluating earthquake hazard in the peninsula.