Don and others...there has been a 7.0 and a 7.1 at the trench south of Honshu.The first one, the 7.0, has a moment tensor solution-either thrust on a N-dipping fault (gently to moderately dipping) or reverse on a moderately S-dipping fault. The subduction zone dips NNW. So, having 2 of these is interesting. A swarm, just a pair, or is something bigger going on. Maybe someone (Don) may want to look at whether the last great earthquake on this part of the subduction zone was preceded by anything, and when the last great earthquake here was.....and what the convergence rate was. Reason is...is convergence rate is 10 cm/yr, and it has been 100 years since last big one, then there are 10 m of accumulated strain..enough for a M8...(I did not check what the rated is or when the last intraplate rupture was).
Chris