Harmonic Tremor can be appeared before the eruption.
https://en.wikipedia.org/wiki/Harmonic_tremor
A harmonic tremor is a sustained release of seismic and infrasonic energy typically associated with the underground movement of magma, the venting of volcanic gases from magma, or both. It is a long-duration release of seismic energy, with distinct spectral lines, that often precedes or accompanies a volcanic eruption.
Today’s seismograph of Mt Rainier
Space Traveler in Alabama 