Nucleation speed limit on remote fluid-induced earthquakes.

The mechanisms behind earthquakes triggered by distant seismic events remain unclear. While seismic waves can temporarily stress the crust, observed delays in earthquake initiation are not easily explained by these transient stresses. Some studies report delays lasting hours or days after seismic waves pass. These delays challenge the assumption that seismic waves alone trigger such events. Prior research has shown that distant earthquakes can influence pore fluid pressure and distribution in the crust. Earth's crust contains isolated, pressurized fluid compartments bounded by low-permeability rock. Seismic shaking can alter rock permeability, potentially releasing overpressurized fluids. These fluids may then infiltrate faults and reduce their strength, possibly leading to earthquakes.

This study aims to explain the observed delays between seismic wave passage and earthquake initiation. The researchers investigate whether these delays can be attributed to fluid diffusion processes. They consider the role of pressurized fluid compartments in the crust. The study focuses on how changes in permeability affect fluid movement and fault strength. It examines whether fluid diffusion can account for the magnitude-dependent delays. The researchers also assess the relevance of these findings to human-induced seismicity. The goal is to determine if a critical nucleation zone model applies to both natural and induced earthquakes. The study seeks to clarify the relationship between fluid dynamics and earthquake nucleation.

The researchers analyzed earthquake data with reported delays after seismic wave passage. They examined the correlation between delay times and earthquake magnitudes. A fluid diffusion model was used to simulate the behavior of pressurized fluid compartments. The model considered changes in permeability caused by seismic shaking. The study incorporated known properties of crustal fluid compartments and fault systems. The researchers tested whether the model could replicate observed delay patterns. They evaluated the fit between modeled and observed nucleation times. The analysis included comparisons with human-induced earthquake data to test the model's applicability.

The study found that delays between seismic wave passage and earthquake initiation increase with magnitude. The best fit for these delays was achieved using a fluid diffusion model. The model suggests that unlocking a critical nucleation zone is necessary for rupture. The delay times align with the time required for fluids to diffuse through low-permeability boundaries. The study shows that permeability changes caused by seismic waves can release overpressurized fluids. These fluids may then infiltrate faults and reduce their strength. The results support the idea that fluid dynamics play a key role in earthquake nucleation. The model also fits data from human-induced earthquakes, suggesting a shared mechanism.

The researchers propose that fluid diffusion processes explain the observed delays in earthquake initiation. They suggest that unlocking a critical nucleation zone is essential for rupture to occur. The study supports the idea that pressurized fluid compartments influence fault behavior. The findings align with the known effects of seismic waves on rock permeability. The model fits both natural and human-induced earthquake data. The study highlights the importance of considering fluid dynamics in earthquake mechanics. The results suggest that fluid release and diffusion are key factors in delayed earthquake nucleation. The researchers do not claim that fluid processes are the only mechanism for earthquake triggering.