Beth,
(your post is pretty far down the page and I I almost did not notice it).

I don't think the 5.3 had anything to do with the later 7.7, except they are both on the Pacific-North American plate boundary.
"the build up" is probably not how most plate boundary quakes occur: there is a constant build up. Some quakes, like the M7.4 before the M9 Tohoku Japan quake, may start or be part of some sort of slow slip that could be considered a build-up. But the M5.3 was not big enough and was too far away to do much, at least the way most fault scientists would look at things today.

Chris