ALT Conceptual model of fluid release events. (a) Hydrothermal seal consolidation causes a drop in high frequency (HF) noise associated with near-surface fluid movement, relative to medium frequencies (MF), which are reflective of fluid movement beneath the seal (HF and MF do not occur at the same spot spatially). This causes an increase in the Displacement Seismic Amplitude Ratio (DSAR). (b) The sealed system traps fluid and builds pressure. Fluid movement in the reservoir and vent is reduced, and the DSAR signal may decline due to the seismic quietness. (c) A gas pulse, or some other mechanism, causes the seal to break, indicated by a peak in the seismic signal. The break could propagate causing pressurized fluids to migrate to the surface generating a fluid release event (or a phreatic eruption). In the hours and days after the event, the discharge slows and this may be evident as an exponential decay of the tremor signal (RSAM).