Conductivity Anomalies in Australia and the Ocean Effect

An Interpretation of the Induction Arrows at Indian Stations

“…SRIVASTAVA et al (1974b) found that along the AlibagHyderabad-Kalingapatnam profile, the negative Z variations for positive H variations and negative D variations, become positive at a distance of about 100 km east of Hyderabad due to ocean effect from the east coast. Since larger Sq(Z) values are also observed near the east coast (Kalingapatnam), the induced electric currents along the east coast will again concentrate along and near the coastline in the seawater as well as in the steplike structure in the conductive upper mantle, and flow from north to south (the upper mantle being elevated under the sea, as was pointed out by PARKINSON (1962PARKINSON ( , 1963). Hyderabad turns out to be an ideal inland low-latitude station, outside the influence of the day-time equatorial electrojet and the oceanic induced electric currents.…”

The geomagnetic coast effect

“…The continental shelf is moderately narrow around the southern half of Australia, if Bass Strait is considered part of the continent. The GCE seems to be normal in the southwest and southeast [Parkinson, 1964;Bennett and Lilley, 1971; Lilley and . The Otway anomaly, on the SW coast of Victoria, interferes with the normal GCE only locally.…”

Geomagnetic variation anomalies in the Koyna and the Bhadrachalam seismic areas in Peninsular India.

“…While the enhancement of Z-amplitudes of short-period (less than one hour) geomagnetic variations near the coastline is directly attributed to induced electric currents in the conducting sea-water, the increase in the value of long-period Z varitions Zr near the coast is associated with an upwelling of conductive mantle under the ocean near a coastline (continental shelf), so that the longperiod induced currents underneath the oceans would flow quite close to the earth's surface and affect Zr values observed near a coastline (PARKINSON, 1964;SCHMUCKER, 1964;LAMBERT and CANER, 1965).…”