  We report on slow earthquakes in Northern Cascadia, and show that continuous
seismic energy in the subduction zone follows specific patterns leading to
failure. We rely on machine learning models to map characteristic energy
signals from low-amplitude seismic waves to the timing of slow slip events.
  We find that patterns in seismic energy follow the 14-month slow slip cycle.
Our results point towards a recurrent build-up in seismic energy as the fault
approaches failure. This behavior shares a striking resemblance with our
previous observations from slow slips in the laboratory.
