Nothing to HAARP about!
Seen on multiple nodes managed by different institutions, feeding back to the CERI / Midwest USGS official charts across the region… what can only be described as low end vibrations, over a VERY large area.
NOT to be confused with earthquakes elsewhere around the planet, this is something I have not seen before over such a wide area.
Did the sensor network undergo some kind of damage? Is there some kind of interference happening? Is this a REAL detection of low frequency vibrations occurring?