High Quality Content by WIKIPEDIA articles! Episodic tremor and slip (ETS) is a phenomenon observed in seismology describing a particular type of tremor pattern observed in regions of convergent plate boundaries. These are characterised by non-earthquake-like tremors, accompanied by aseismic slip in the same region of the local megathrust. For some areas around the ETS, there is an apparent slipping back or reversal of direction of the normal tectonic plate movement, although the fault motion remains consistent with subduction.