That's helpful information. It doesn't invalidate the concern, however, since very large earthquakes are often preceded by moderately large foreshocks, so there is an now a temporarily elevated risk of a very large earthquake in that region.
Last night, it was long enough for me to sit up in bed, wait for a while, get up, stand in the living room for a while, and then go upstairs to where my daughter and one-year-old grandson were sleeping, with the shaking and rattling continuing the whole time. After it stopped, we all went back to bed.
In 2011, I happened to leave Yokohama for Osaka by train on the morning of March 11 and missed the big one by just a few hours. I'm hoping to be away when the next big one hits, too.