The Cascadia Subduction Zone is a massive geologic fault that last ruptured in January 1700. But while this fault has stayed quiet for centuries, it regularly generates small tremors that accompany gradual, nondisruptive movement along the fault. The tiny tremor events and slow slippage are known collectively as “episodic tremor and slip.” Seismic waves associated with these tremor events are recorded and tracked by the UW’s Pacific Northwest Seismic Network.