3 were at 5:5 magnitude...that got a few folks paying attention. If you want a clue, look at the depths. Quakes are typically recorded in km from - (neg. "above sea level)to a depth of around 600 km and are given in decimals. When you see similar magnitude quakes at specific depths, like 5k or 10k more often than not you are looking at targeted events either for exploration or termination of underground facilities.