An explanation of induced magnetic variations at Sabhawala,India

Induction vectors calculated for short-period events such as “bays” and “storm sudden commencements” (SSCs) indicate that the conductor causing the anomaly lies to the south of Sabhawala. The nature of vertical transfer functions obtained from spectral analysis of storm-time variations further confirms the presence of such a conductor. The nature of maximum (G_p) and minimum (G₁) response functions suggests that a two-dimensional conductor south of Sabhawala is responsible for anomalies in Z. Invoking a structural model of the Earth's crust beneath the Himalayas, in keeping with accepted orogenic theories, we propose that one structure capable of producing the desired conducting path is a rise of the asthenosphere south of the Himalayan range. Another important factor contributing to the induced variations at Sabhawala is due to a sedimentary trough running parallel to the Himalayas, again to the south. These views are confirmed by a two-dimensional model calculation. It is found that the undulation of the asthenosphere alone does not reproduce the nature of the anomalies in H and Z.