On Fluid-Metamorphic Regime of Deep Fault Zones, in Connection with “Topical Issues in Hydrogeology of Seismogenic Fault Zones” by G. G. Kocharyan and I. V. Shatunov

Abstract—In many aspects, the deep fluid regime plays a key role in seismicity, aseismic deformation of the lithosphere, and ore and oil genesis processes. An informative detailed analysis of the hydrogeology of shallow fault zones is presented in (Kocharyan and Shatunov, 2024), where it is noted that little is known about the character of the fluid dynamics of deep faults. This paper focuses mainly on the challenges of describing deep fault zones and highlights a number of inconsistencies that arise in this consideration. It is shown that the difficulties inherent in such a description are largely overcome by accounting for the processes of metamorphism and associated anomalies in the physical properties of the Earth’s interior. Further refinement is given to the proposition that earthquakes occurring at different depths have different physical mechanisms.