Hello Mary,

While I don't know the answer, I can guess-I think there is a comparable chance of something larger for a 3.9 than a 5. But, a 4.5 is larger than a 3.9, and is not a big deal. I think he's thinking is there was a >5, there might be static stress changes that could trigger earthquakes over a larger area. But, for a 3.9, there would be some stress changes in the immediate vicinity (probably meaning within a few km, which could mean on the same fault) Chris