see this USGS note on the subject). Earthquakes happen when they happen.
Supermoons are only a bit larger than the average size of the disk of the moon in the sky, around 10-11%, but a fair bit brighter, about 30%. You can compare the full moon from tonight (above) with the size of the moon just prior to the lunar eclipse of April 2015 (below). Still, "they" are saying this is the closest the moon has been to the Earth since 1948. I guess that is something.