EGU23-626, updated on 22 Feb 2023
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Is secondary mineralization playing a pivotal role in recurring seismicity at Koyna-Warna Seismogenic Region of India: a geochemical perspective?

Piyal Halder1,2, Anupam Sharma1,2, Matsyendra Kumar Shukla3, and Kamlesh Kumar1,2
Piyal Halder et al.
  • 1Birbal Sahni Institute of Palaeosciences (DST, Govt. of India), Lucknow-226007, Uttar Pradesh, India
  • 2Academy of Scientific and Innovative Research (AcSIR), Ghaziabad- 201002, India
  • 3Govt. of India, Ministry of Earth Sciences (MoES), Borehole Geophysics Research Laboratory (BGRL), Karad-415105, India

Since the impoundment of the Shivajisagar Reservoir behind the Koyna Dam in 1962, numerous earthquakes have been felt in the Koyna-Warna Seismogenic Region of Western India. The mesoscopic and microscopic observations on the basement granitoid core samples, recovered under the Continental Deep Drilling Program of the Ministry of Earth sciences, reveal the precipitation of calcite and the formation of clay minerals (illite and chlorite) along the fractures and faults. The presence of these secondary minerals alongside the primary minerals like quartz and feldspar is further supported by X-ray Diffraction, which also points to the fracture scale chemical alteration as a result of fluid-rock interactions. It's interesting to note that the precipitation of these hydrophilic clay minerals along faults and fractures might promote slip by raising fluid pressure and lowering the shear strength of the faults. Thus, secondary mineralization due to fluid-rock interaction may have a contribution to the release of strain in form of seismic tremors. On the other hand, the neoformation of these hydrophilic clay minerals along fault/fracture surfaces may also cause rheological incongruity, which could lower the density as well as P and S wave velocities. Besides, hydrogen atoms in clay-bound water may influence neutron capture, leading to over-optimistic estimations of neutron porosity. Additionally, our study supports past geophysical anomalies found in the KFD1 borehole and infers that the geophysical anomalies correlating to the growing fracture density and fault system of the basement rocks are caused by chemical alteration due to fluid-rock interaction and subsequent secondary mineralization. So, this research offers important new understandings of geochemical activity in the context of geophysics and serves as a bridge between geochemistry and geophysics.

How to cite: Halder, P., Sharma, A., Shukla, M. K., and Kumar, K.: Is secondary mineralization playing a pivotal role in recurring seismicity at Koyna-Warna Seismogenic Region of India: a geochemical perspective?, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-626,, 2023.