Sky Quakes, Broken Gear, or Something Else.

[guyfriday]

Another thing regarding lightnings.

As I said, they are a local event, and most are cloud-to-cloud, so they would not trigger seismographs several miles away.

Also, being an event with an extremely fast start, it would be recognisable on a seismogram.

I know, but given the weirdness of these events, it's worth trying to rule items out.