Mid-Ocean Ridge Eruptions: Timing and Processes Inferred from Two Decades of Earthquake Monitoring

Abstract:

Two decades of hydroacoustic monitoring combined with in situ OBS and OBH experiments have identified nine seismically well-defined seafloor events at mid-ocean ridges with characteristics consistent with eruptive activity. The majority of these events occurred at fast and intermediate spreading ridges, where eruption recurrence rates are expected to be higher. Most have also been verified as eruptions through direct seafloor observations. This suite of crustal accretion events, when examined together, suggest patterns of activity that are influenced by both short and long term tidal forces. Tidal triggering of earthquakes in the mid-ocean ridge environment is well established, but until recently data has been lacking on the timing of seafloor eruptions with which to make statistically robust inferences. OBS and OBH earthquake data on the East Pacific Rise and Axial volcano both indicate a steady increase in the rate of seismic activity preceding an eruption, consistent with an increasing state of stress of the system. All of these observations are consistent with a model of crustal accretion that is sensitive to small perturbations in loading both in the short and longer term. Implications of this sensitivity will be presented along with observations to support it.