Current Science

D. Srinagesh ¹, Prantik Mandal ¹, R. Vijaya Raghavan ¹, Sandeep Gupta ¹, G. Suresh ¹, D. Srinivas ¹, Satish Saha ¹, M. Sekhar ¹, K. Sivaram ¹, Sudesh Kumar ¹, P. Solomon Raju ¹, A. N. S. Sarma ¹, Y. V. V. S. B. Murthy ¹, N. K. Borah ¹, B. Naresh ¹, B. N. V. Prasad ¹, V. M. Tiwari ¹

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

Abstract

According to the Gutenberg–Richter law¹, at least one earthquake of magnitude greater than 7 occurs every month along the seismically active belts in the world. Earthquakes are the manifestation of fault slip at depths, thus, there is no direct method to measure or observe them. However, seismometers can record ground velocity or acceleration caused by the occurrence of an earthquake when a fault slip occurs at depth. Therefore, setting up a seismic network is inevitable to understand the physics of earthquake processes, thereby, mitigating earthquake hazard.

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E. V. S. S. K. Babu ¹, V. M. Tiwari ¹, Somnath Dasgupta ²

Affiliations
1 CSIR-National Geophysical Research Institute, Uppal Road, Hyderabad 500 007, IN
2 Indian Institute of Science Education and Research, Kolkata, Mohanpur, Nadia 741 246, IN

Abstract

Understanding the geodynamic processes that underpin the formation of continents is fundamental to decoding the complex evolutionary history of the Earth and the terrestrial planets. In the Phanerozoic Eon, the paradigm of plate tectonics and Wilson-cycle processes not only constitutes a robust and unifying mechanism to explain the orogenic processes of crust formation, recycling and preservation, but also the complex interactions among the solid earth, biosphere, hydrosphere and atmosphere relevant to evolution of life and climate. However, there is yet no consensus on a global geodynamic framework for the Hadean and Archean Eons.

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D. Srinagesh ¹, Dhiraj Kumar Singh ¹, G. Vikas ¹, B. Naresh ¹, Sunil Roy ¹, Y. V. V. B. S. N. Murthy ¹, P. Solomon Raju ¹, G. Suresh ¹, Prantik Mandal ¹, A. N. S. Sharma ¹, M. Shekar ¹, V. M. Tiwari ¹

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

Abstract

The present study focuses on the recent earthquake activity in Palghar region, Maharashtra, India. Until 31 August 2019, a total of 4854 earthquakes have been located here, whose local magnitude (M_L) varied from 0.1 to 4.1. Majority of the earthquakes (~94%) were located in the depth range 4–16 km. The precise earthquake relocations reveal two clusters. The N–S trending cluster north of 20.04°N extends to a depth of 10 km, whereas the NE–SW trending cluster to the south of 20.04°N extends to 16 km depth. The shallow northern cluster is noticed to be sandwiched between two mapped mafic intrusions, whereas the deeper southern segment shows earthquakes clustering around the mafic intrusion. The modelled composite focal mechanism solutions for both the north and south clusters suggest normal faulting with a minor strike–slip component as the dominant deformation mode for the Palghar region. From relocated seismici-ty, we have detected a deeper seismically active zone (with M> 3) at 4–16 km depth, occupying a crustal volume of 1440 km 3 (i.e. 20 km (in N–S) ×6 km (in E– W) and 12 km (in depth)) that dips toward 20°S and 70°W. This could be attributed to the large crustal stresses induced by the mafic intrusive body below the region.

Keywords

Crustal Stress, Deformation Mode, Earth-quake, Mafic Intrusion, Relocations, Seismic Activity.

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G. Ashok Babu ¹, G. Vamsi Krishna ¹, V. M. Tiwari ¹, R. Antony ², C. S. Suraj ², K. T. Vikas ², P. V. S. Murthy ²

Affiliations
1 CSIR-National Geophysical Research Institute, Hyderabad 500 007, IN
2 CSIR-National Aerospace Laboratories, Bengaluru 560 017, IN

Abstract

No Abstract.

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