Permeability and seismicity rate changes at an inflating submarine volcano caused by dynamic stresses

Transient stresses from the passage of seismic waves are known to trigger earthquakes and cause crustal permeability changes. However, whether permeability change is a main driver of dynamic earthquake triggering remains debated. Our understanding of the characteristics of dynamic triggering in submarine volcanic environments is also limited due to the lack of offshore observations. Here, we utilize a high-resolution micro-seismicity catalog from July 2015 to July 2022 to evaluate the triggering response of Axial Seamount, an inflating and seismically active submarine volcano located in the northeast Pacific Ocean. We report statistically significant episodes of dynamic earthquake triggering for ∼18 % of the teleseismic events investigated, which is comparable with subaerial tectonic and volcanic environments. We do not observe any obvious dependence of triggering rate on the amplitude of peak ground velocity. However, a comparison of the triggering rate and the cumulative magma volume shows that the triggering susceptibility might increase as the volcano becomes more critically stressed. Using data recorded by a temperature sensor in a black smoker, we compute the phase lag between hydrothermal vent-fluid temperature and tidal loading amplitude before and after the arrival of teleseismic waves to probe the relationship between permeability change and dynamic triggering. While the energy density thresholds for dynamic earthquake triggering and permeability change are comparable, both triggering and non-triggering observations show similar proportions of permeability changes. Our results suggest that permeability change induced by transient stresses might not be a necessary or primary mechanism that drives dynamic earthquake triggering.