What triggers seismicity thousands of kilometers away from a mainshock?

Remotely triggered earthquakes have emerged as a compelling yet puzzling phenomenon for advancing seismic-hazard forecasting. Here, we propose a unifying mechanism to explain their enigmatic behaviors, that is, the pore-pressure dynamics in fault gouge. Using a bounding surface model rooted in critical-state soil mechanics, we embed gouge deformation into a computational framework that tracks stress evolution under the perturbation of teleseismic waves. Our simulations reveal that dynamic loading drives pore-pressure increases several times larger than the applied stress amplitude, thus markedly weakening the fault and enabling failure under minimal perturbations. Also, we show that compressional components of the waves amplify pore pressure far more than shear components, explaining the superior triggering capacity of Rayleigh waves over Love waves. Given that pore pressure dissipates slowly in low-permeability gouge, weakening persists well beyond the transient forcing, promoting elevated seismicity after wave passage. Together, these results establish fault-gouge pore-pressure dynamics as a fundamental mechanism for remote earthquake triggering.