Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

B. S. Sukhija ¹, M. N. Rao ¹, D. V. Reddy ¹, P. Nagabhushanam ¹, B. V. Lakshmi ¹, H. K. Gupta ¹

Affiliations
1 National Geophysical Research Institute, Hyderabad-500 007, IN

Abstract

Paleoseismic investigations so far carried out in India are spread over two tectonically distinct areas, viz., the interplate seismic zone of Himalaya and the intraplate Stable Continental Region (SCR). Most of the reported paleoseismicity studies provided geological evidences like soft sediment deformation, paleoliquefaction features (like sand dykes, sand blows etc), small scale folding, faulting with disptacement of beds etc. Though the evaluation of recurrellce period of destructive seismic events is a pre-requisite for paleoseismology, no paleoseismic study in India so far has provided information on the recurrence period, except for the detailed study in the Shillong plateau, which suggested recurrence period of 400-600 yrs for major earthquakes.

Keywords

Paleoseismology, Earthquake Hazard, Recurrence Period, Himalaya, Stable Continental Region.

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D. Lal ¹, M. N. Rao ¹

Affiliations
1 Physical Research Laboratory, Navrangpura, Ahmedabad, IN

Abstract

No Abstract.

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H. K. Gupta ¹, R. K. Chadha ¹, M. N. Rao ¹, B. L. Narayana ¹, P. Mandal ¹, M. Ravi Kumar ¹, N. Kumar ¹

Affiliations
1 National Geophysical Research Institute, Hyderabad - 560 007, IN

Abstract

The Jabalpur earthquake of magnitude 5.8 occurred on May 22, 1997 along seismically active Narmada-Son Lineament (NSL) in central India, with its epicenter about 30 km southeast of Jabalpur. A maximum intensity I_o = VIII on MM scale was observed in Jabalpur and surrounding region. The isoseismal map prepared for this earthquake shows NE-SW trend which in general agrees with the focal mechanism solution indicating thrust faulting along a ENE-WSW fault with minor strike-slip component. Several ground cracks mapped in meizoseismal area show a dominant N75° E trend. The damage pattern of the constructions clearly shows a strong correlation with lithology, structures and soil cover of the area. There are no foreshocks reported for this earthquake and only a few aftershocks are recorded. which warrant a close monitoring of this region.

Keywords

Earthquake, Seismology, Jabalpur.

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R. Mallikharjuna Rao ¹, S. Bhattacharji ², M. N. Rao ¹, J. M. Wampler ³

Affiliations
1 National Geophysical Research Institute, Hyderabad - 500 007, IN
2 Department of Geology, Brooklyn College, City University of New York, Brooklyn, New York 11210, US
3 Department of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, US

Abstract

The Proterozoic intracratonic Cuddapah Basin contains different phases of igneous intrusives associated with sediments and lava flows from Vempalle Formation and basaltic and dolerite sills from Tadpatri Formation which occur in an arcuate fashion parallel to the basin margin. K-Ar ages suggest that the igneous activity commenced at about 1840 Ma after the initial sedimentation in the basin. Some dolerite sills show ages of about 1000 Ma may represent reequilibrated ages and an interesting younger age of 177±7 Ma is obtained for a norite dyke emplaced in the Cumbum shales of Pullampet Formation in Nallamalai Group of sediments. Basaltic lava flows contain plagioclase (39-48% )and clinopyroxene (18-40%) and opaques (1.5-4%), orthopyroxene (1-2%) and olivine (1.5-4%) are the common accessory phases. A few picrite samples occur at the base of sills in the Tadpatri Formation of Chitravati Group showing cumulus textures and contain olivine, orthopyroxene, clinopyroxene and small amounts of plagioclase. The lava flows and the sills exhibit continental tholeiitic nature and range from basalt to basaltic andesite in composition. They are olivine or quartz normative in character with strong magmatic differentiation trend of iron enrichment during their crystalization. The rocks are enriched in light rare earth elements and exhibit positive Eu anomaly (Eu/Eu^*=1.34-2.33). Plagioclase, clinopyroxene ± olivine phenocryst mineralogy, distinctive negative Sr anomaly suggest a relatively low-pressure fractionation during their evolution.

Keywords

Basic Volcanics, K-Ar Ages, Geochemistry, Cuddapah Basin, Andhra Pradesh.

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V. S. Singh ¹, S. C. Jain ¹, T. V. Rao ¹, M. N. Rao ¹, B. C. Negi ¹

Affiliations
1 National Geophysical Research Institute, Hyderabad - 500 007, IN

Abstract

Shales/limestone, which are devoid of primary porosity, often act as the potential aquifers when they are fractured and/or weathered. An integrated approach employing photogeologicil, hydrogeological and geophysical investigations has now been attempted to delineate groundwater potential zones in such shaley limestone terrain at the southern part of Chandrapur District of Maharashtra. This cost-effective approach, which was focussed at sites delineated from aerial photo interpretation has helped in drilling of good yielding wells in an otherwise unpromising shaley limestone terrain.

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