Earthquakes can often change the frequency of eruptions or the amount of water released by geysers. Why do you think this is?
Like volcanoes, geysers and hot springs have a plumbing system. Earthquakes can easily change the shape of this system, resulting in changes in the eruption period. Water erosion also changes a geyser's plumbing over time, usually causing its eruptions to decrease in frequency. This is why Old Faithful is slowing down.
fracture networks and pressure (stress) systems change when an earthquake happens. These changes can make it either easier for fluids to migrate, or harder to migrate, depending on the nature of the associated changes.