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Harsh Gupta ¹, D. Shashidhar ¹, Metilda Pereira ¹, N. Purnachandra Rao ¹, D. Nagesh ¹, H. V. S. Satyanarayana ¹, Satish Saha ¹, R. T. Babu Naik ¹, V. P. Dlmri ¹

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

Abstract

No Abstract.

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P. S. Raju ¹, R. V. Raghavan ¹, E. Umadevi ¹, D. Shashidar ¹, A. N. S. Sarma ¹, D. Gurunath ¹, H. V. S. Satyanarayana ¹, T. Sagara Rao ¹, R. T. Babu Naik ¹, N. Purnachandra Rao ¹, M. D. Kamuruddin ¹, U. Gowri Shankar ¹, N. K. Gogi ¹, B. C. Baruah ¹, N. K. Bora ¹, M. Kousalya ¹, M. Sekhar ¹, V. P. Dimri ¹

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

Abstract

No Abstract.

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Harsh K. Gupta ¹, T. Harinarayana ¹, M. Kousalya ¹, D. C. Mishra ¹, Indra Mohan ¹, N. Purnachandra Rao ¹, P. S. Raju ¹, B. K. Rastogi ¹, P. R. Reddy ¹, D. Sarkar ¹

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

Abstract

No Abstract.

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Harsh Gupta ¹, N. Purnachandra Rao ¹, D. Shashidhar ¹, K. Mallika ¹

Affiliations
1 National Geophysical Research Institute, Council of Scientific and Industrial Research, Uppal Road, Hyderabad-500007, IN

Abstract

On 12 May 2008 an earthquake of magnitude 7.9 devastated the Northwestern Sichuan province of China. This earthquake occurred along the northeast trending Longmenshan fault bordering the Tibetan plateau on the west and the Sichuan Basin on the east. The focal mechanism depicts a thrust fault mechanism with the Northwest dipping fault plane correlating well with the tectonic fault. This plane also hosts a component of right-lateral strike slip consistent with the local tectonics and orients well along the trend of aftershock distribution. Broadly, the Sichuan earthquake is a consequence of the northward convergence of the Indian plate against the Eurasian plate resulting in eastward crustal extrusion of Tibetan plateau accompanied by clockwise rotation of several tectonic blocks of the Eurasian landmass. More specifically, it occurred along the Northeast trending Longmenshan fault, due to over-thrusting of a weak Tibetan crustal block over a mechanically stronger Sichuan Basin. Estimation of p value using about 164 aftershock data provides a value of 0.87, comparable to a value of 1.0 obtained for the Muzaffarabad earthquake in western Himalaya, indicating a normal rate of decay of the aftershocks in the months ahead. We infer that aftershocks of magnitude exceeding 5 may occur for a duration of about 7 months.

Keywords

Earthquake, Seismicity, Tibetan Plateau, Siachun, China.

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Harsh Gupta ¹, D. Shashidhar ², K. Mallika ², N. Purnachandra Rao ², D. Srinagesh ², H. V. S. Satyanarayana ², Satish Saha ², R. T. B. Naik ²

Affiliations
1 National Geophysical Research Institute (Council of Scientific and Industrial Research), Uppal Road, Hyderabad - 500 007, IN
2 National Geophysical Research Institute (CSIR), Uppal Road, Hyderabad - 500 007, IN

Abstract

Earthquake activity is monitored in real time at the Koyna reservoir in western India, beginning from August 2005 and successful short term forecasts have been made of M ∼ 4 earthquakes. The basis of these forecasts is the observation of nucleation that precedes such earthquakes. Here we report that a total of 29 earthquakes in the magnitude range of 3.5 to 5.1 occurred in the region during the period of August 2005 through May 2010. These earthquakes could broadly be put in three zones. Zone-A has been most active accounting for 18 earthquakes, while 5 earthquakes in Zone-B and 6 in Zone-C have occurred. Earthquakes in Zone-A are preceded by well defined nucleation, while it is not the case with zones B and C. This indicates the complexity of the earthquakes processes and the fact that even in a small seismically active area of only 20 km x 30 km earthquake forecast is difficult.

Keywords

Earthquake, Nucleation, Forecast, Koyna Reservoir, Maharashtra.

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Harsh Gupta , Shailesh Nayak , Y. J. Bhaskar Rao , R. K. Chadha , B. K. Bansal , D. Srinagesh , N. Purnachandra Rao , Sukanta Roy

Abstract

No Abstract.

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N. Purnachandra Rao ¹, M. Ravi Kumar ¹, Kusumita Arora ¹

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

Abstract

A surprising discovery of a massive, ancient, subducted tectonic slab in the southeastern Indian Ocean, known as the southeast Indian slab (SEIS), encompassing the entire mantle down to the earth's core raises a whole set of new questions, and offers opportunities to answer some previously outstanding ones. Evidence for SEIS comes from a high-resolution tomographic study by Simmons et al.

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D. S. Suresh Babu ¹, D. Padmalal ¹, N. Purnachandra Rao ¹

Affiliations
1 National Centre for Earth Science Studies, Ministry of Earth Sciences, Akkulam, Thiruvananthapuram 695 011, IN

Abstract

In India, the demand for freshwater resources is increasing every year because of population rise and rapid economic development. This warrants the imminent need for better evaluation of all the available sources of freshwater and their discharge–recharge mechanisms for planning sustainable development strategies in the country. Among different sources, groundwater constitutes about 97% of the earth’s liquid freshwater in the hydrologic cycle. It has now been realized that as part of the hydrologic cycle, a significant amount of groundwater flows directly into the sea through porous rocks and sediments¹. This component is called submarine groundwater discharge (SGD). In a study carried out in the southern United States using ²²⁶Ra as tracer², it was reported that the contribution of SGD in the coastal waters of the area could be comparable to the observed discharge from rivers³. Although India has an extensive coastline of about 7500 km, except selected case studies^4–10, no systematic efforts have hitherto been made to assess SGD flux to its receiving coastal waters. As the country is undergoing rapid economic development in the recent years, it is high time that the scientific community make efforts to estimate the quantity and quality of SGD flux to the Indian seas for planning and development of its freshwater potential.

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