Role of hydrothermal alteration and thermally activated healing on earthquake dynamics along oceanic transform faults

The generation of earthquakes is primarily governed by the thermo-mechanical and structural properties of fault zones. However, the influence of lithological and hydrothermal factors on the rupture style, size, and recurrence patterns of seismic activity remains poorly understood. Here, we explore the role of hydrothermal alteration on the spatial distribution and source characteristics of earthquakes along oceanic transform faults. We perform three-dimensional seismic cycle simulations calibrated with thermal profiles from thermo-mechanical geodynamic models and laboratory-derived frictional properties of crust and mantle rocks to elucidate the seismic patterns of oceanic transform faults. The thermally activated healing of antigorite in serpentinized mantle pockets may facilitate the spontaneous generation of seismic swarms, depending on the intensity of shear heating and the activation energy of the healing process. Fluid circulation influences seismic behavior by driving local alteration, affecting fault frictional properties. The unstable nature of gabbro friction over a finite range of temperature supports a narrow seismogenic zone within the oceanic crust, with a lateral extent of seismic ruptures limited by patches of hydrothermal alteration products (e.g., talc and chlorite) within the fault zone. Abundant microseismicity may occur within partially altered, heterogeneous barrier zones. These findings highlight the critical interplay between lithology, hydrothermal processes, and fault mechanics, providing new insights into the tectonic framework of seismicity along oceanic transform faults.