In this figure from Chlieh et al (2014), ‘ISC’ means inter-seismic coupling. If it is red (1.0), the megathrust is stuck and must produce quakes; if blue (0.0), the plate is freely slipping and so large quakes will not strike. Notice that this model shows the site of the 2016 quake is blue (at the site of the 1942 star), which the quake just proved incorrect. Science is hard.