The fault segment that ruptured this week in Chile was identified in a paper last year as having strain buildup that, in a 'worst-case' situation, was ready to produce up to an 8.5 magnitude earthquake. [right, Fig 1 from the paper. Circles are GPS stations, stars are major historical earthquakes, ellipses show rupture areas]
The authors conclude that "The Concepción–Constitución area [35–37◦S] in South Central Chile is very likely a mature seismic gap,
since no large subduction earthquake has occurred there since 1835." The amount of convergence exceeds more than 10 m since the last major interplate quake of 170 years ago.
Ref: Interseismic strain accumulation measured by GPS in the seismic gap between Constitución and Concepción in Chile, J.C. Ruegga, A. Rudloff b, C. Vignyb, R. Madariagab, J.B. de Chabaliera, J. Camposc, E. Kauselc, S. Barrientosc, D. Dimitrovd, Physics of the Earth and Planetary Interiors 175 (2009) 78–85