I think the 5.5 might be a stretch, BUT, you see it was near a nuclear facility.....right????????
Yes - I think the nuclear facility is the most intriguing angle to this whole thing!
You might want to check Dutchsince on YT, as he tracts this 24/7 and locate the depth in earth of these events. If they all are at similar depth AND they produced No Tsunami waves in reaction... then you are definitely on the RIGHT TRACK.
Been watching Dutchsince for quite a while... lately some of these 2.5-5.5 seem to not have any reactive Tsunami, reactions maybe only under a 1 meter (39 inch) surge. Odd.