Investigations related to scientific deep drilling to study reservoir-triggered earthquakes at Koyna, India

Abstract

high-quality magnetotelluric data at 100 stations, provide both regional information about the thickness of the Deccan Traps and the occurrence of localized density heterogeneities and anomalous conductive zones in the vicinity of the hypocentral zone. Acquisition of airborne LiDAR data to obtain a high-resolution topographic model of the region has been completed over an area of 1,064 km 2 centred on the Koyna seismic zone. Seismometers have been deployed in the granitic basement inside two boreholes and are planned in another set of six boreholes to obtain accurate hypocentral locations and constrain the disposition of fault zones.

Exploration of deep terrestrial subsurface microbiome in Late Cretaceous Deccan traps and underlying Archean basement, India

“…In contrast to our understanding of structure and function of deep subsurface microbial community through all these studies, the microbiome of Deccan subsurface remains elusive. In this work, we try to demonstrate the nature and function of microbial communities within the deep terrestrial subsurface of Deccan traps using the rock cores recovered through scientific deep drilling 39 , 40 . Exploration of deep biosphere of granitic-basaltic crustal system is highly imperative to answer the fundamental questions on microbial life within deep, dark, oligotrophic crust, their mode of interaction and role in Earth’s biogeochemical processes, origin of life on Earth and even on extra-planetary locations (e.g., Mars).…”

“…Scientific deep drilling in the Koyna-Warna region of Deccan traps, western India provides a unique opportunity to investigate microbial life within deep terrestrial igneous rocks (basalts and granite-gneiss basement) 39 , 40 . The Deccan traps represents a continental flood basalt province covering an area of over 0.5 million km 2 of lava flows (~65 Ma) with a total thickness of over 2000 m near the eruptive centre in western India 41 – 44 .…”

“…This thick pile of Deccan basalts rests on ~2.5 Ga Archean crystalline basement 45 . The Koyna-Warna region has gained further importance owing to the reservoir triggered seismicity ever since the impoundment of the Koyna dam in 1962 39 . Exploratory core drilling has been carried out at multiple sites in the Koyna seismogenic zone to ascertain the subsurface geology and structure in the region and carry out seismological investigations.…”

“…Exploratory core drilling has been carried out at multiple sites in the Koyna seismogenic zone to ascertain the subsurface geology and structure in the region and carry out seismological investigations. The boreholes penetrated the entire thickness of Deccan traps (412–1251 m) and passed through a few hundred meters of the underlying granitic basement 39 , 46 . Study of drill cores also reveal that the transition of Deccan basalts to granitic basement rock occurs over a relatively short span of few tens of centimetres to few meters 47 , 51 .…”

Remote Triggering in the Koyna‐Warna Reservoir‐Induced Seismic Zone, Western India

“…In our case, the Koyna‐Warna region had a complex case of RIS, involving rapid (Gupta, ) and delayed triggering of microseismicity (Simpson, ; Simpson et al, ). The granitoid basement in the region is highly fractured, as revealed from borehole core samples (Gupta et al, ; Roy et al, ) as well as relatively high levels of background seismicity (Gupta, ). Our observation is generally consistent with recent findings of remote triggering in other intraplate regions with anthropogenic activities (e.g., Han et al, ; van der Elst, Savage, et al, ; Wang et al, ).…”