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

An Interpretation of the Induction Arrows at Indian Stations

“…1. This will explain the reversed coast effect observed at Alibag for events like SSCs and bays with larger negative Z amplitudes near the coast for positive H variations (SRIVASTAVA et al, 1974a) and larger Sq(Z) values at Alibag as compared to Hyderabad (SRIVASTAVA, 1970). The current concentration is expected to turn westwards from the coast near Calicut (SRIVASTAVA and SANKER NARAYAN, 1969).…”

“…Introduction The geomagnetic induction anomalies in India were discovered more than a decade ago (SRIVASTAVA, 1966;SANKER NARAYAN, 1967, 1969). This was followed by more intensive investigations for the delineation of the anomalies and also for better appreciation of the oceanic and subsurface causes of the amonalies identified mostly from the records of the permanent magnetic observatories in Peninsular India (SRIVASTAVA, 1970(SRIVASTAVA, , 1977aSRIVASTAVA et al, 1974a, b;NITYANANDA et al, 1977). We now have in the longitude zone 72E-80E in India, a chain of ten magnetic observatories from Gulmarg in the Kashmir Himalaya (very recently established by the Indian Institute of Geomagnetism) and Sabhawala (operated by the Survey of India since 1963) in the Himalayan foothills and close to the Sq focus in the north, down to Trivandrum on the seacoast in the extreme south.…”

Geomagnetic induction anomalies in India in relation to geology

“…The enhancement of both short-period and long-period Z-variations at LoniKalbhor (110 kmfrom the west coast), in the case of the western 'ghats' (Figure 1) seems to be mostly controlled by the orogeny of the western 'ghats' (Srivastava et al, 1974a), The prevailing orogeny effect at Loni-Kalbhor is mixed up with the so-called coastal effect. A N-S conductive structure well below the western 'ghats' could be associated with the orogeny.…”

“…geomagnetic induction anomaly in short-period events and daily variation data respectively and established the existence of a coastal effect at Alibag. Later, Srivastava and Sanker Narayan (1967, 1969, Srivastava et al (1974a, b) and Srivastava and Prasad (1974), Nityananda et al (1975Nityananda et al ( , 1977Nityananda et al ( , 1981, Rajagopal et al (1976), Singh et al (1977), Srivastava (1977Srivastava ( , 1981, Rajaram et al (1979), Agarwal et al (1979) and Srivastava and Abbas (1980) investigated various aspects of geomagnetic induction anomalies in India. Based on detailed magnetometer array studies in India, exhaustive results have been reported by Lilley et al (1981), Thakur et al (1981) and Arora et al (1982).…”

“…Subsequent computations based on transfer function and Wiese vector techniques respectively, gave the induction arrows at these stations (Nityananda et al, 1975;Srivastava and Abbas, 1980), which revised the Parkinson vector determiRations made earlier. Srivastava et al ( , 1974a Srivastava et al, 1974a).…”