Investigations of continued reservoir triggered seismicity at Koyna, India
Harsh K. Gupta, Kusumita Arora, N. Purnachandra Rao, Sukanta Roy, V. M. Tiwari, Prasanta K. Patro, H. V. S. Satyanarayana, D. Shashidhar, C. R. Mahato, K. N. S. S. S. Srinivas, M. Srihari, N. Satyavani, Y. Srinu, D. Gopinadh, Haris Raza, Monikuntala Jana, Vyasulu V. Akkiraju, Deepjyoti Goswami, Digant Vyas, C. P. Dubey, D. Ch. V. Raju, Ujjal Borah, Kashi Raju, K. Chinna Reddy, Narendra Babu, B. K. Bansal, Shailesh Nayak, 2017. "Investigations of continued reservoir triggered seismicity at Koyna, India", Tectonics of the Deccan Large Igneous Province, S. Mukherjee, A. A. Misra, G. Calvès, M. Nemčok
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Koyna, located in the Deccan Volcanic Province in western India, is the most significant site of reservoir triggered seismicity (RTS) globally. The largest RTS event of M 6.3 occurred here on December 10, 1967. RTS at Koyna has continued. This includes 22 M ≥ 5.0 and thousands of smaller events over the past 50 years. The annual loading and unloading cycles of the Koyna Reservoir and the nearby Warna Reservoir influence RTS. Koyna provides an excellent natural laboratory to comprehend the mechanism of RTS because earthquakes here occur in a small area, mostly at depths of 2–7 km, which are accessible for monitoring. A deep borehole laboratory is therefore planned to study earthquakes in the near-field to understand their genesis, especially in an RTS environment. Initially, several geophysical investigations were carried out to characterize the seismic zone, including 5000 line kilometres of airborne gravity gradiometry and magnetic surveys, high-quality magnetotelluric data from 100 stations, airborne LiDAR surveys over 1064 km2, drilling of 8 boreholes of approximately 1500 m depth and geophysical logging. To improve the earthquake locations a unique network of borehole seismometers was installed in six of these boreholes. These results, along with a pilot borehole drilling plan, are presented here.
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Understanding the Deccan Trap Large Igneous Province in western India is important for deciphering the India–Seychelles rifting mechanism. This book presents 13 studies that address the development of this province from diverse perspectives including field structural geology, geochemistry, analytical modelling, geomorphology and geophysics (e.g., palaeomagnetism, gravity and magnetic anomalies, and seismic imaging). Together, these papers indicate that the tectonics of Deccan is much more complicated than previously thought. Key findings include: the Deccan province can be divided into several blocks; the existence of a rift-induced palaeo-slope; constraints on the eruption period; rift–drift transition mechanisms determined for magma-rich systems; the tectonic role of the Deccan or Réunion plumes; sub-surface structures reported from boreholes; the delineation of the crust–mantle structure; the documentation of sub-surface tectonic boundaries; post-Deccan-Trap basin inversion; deformed dykes around Mumbai, and also from the eastern part of the Deccan Traps, documented in the field.