afaict part of the messaging behind this quake is about the worry that big Sanriku earthquakes like this might make it easier for the northeast part of the tren

afaict part of the messaging behind this quake is about the worry that big Sanriku earthquakes like this might make it easier for the northeast part of the trench to unlock (closer to Aomori and Hokkaido, where the Japan Trench starts turning into the Kuril Trench).