This is interesting, since when you look at the earthquake upside-down, from their perspective it is an M7. But from our right-side-up view, it is an M6.2. :)
Anyway, these horrendously deep earthquakes are a bitch to properly size, and the journals can have it. Who cares? As you can see, they have a really active subduction zone, and are sure to get their M9 every 500 years or so. The deep quake probably isn't related to anything since the physics down there gets bizarre, involving phase changes and such. Not good old sliding wet rock!