National Seismic Monitoring Center
Wednesday 26 June 1974
There's something I think you really ought to see. I don't know if it's some kind of instrumental error or what, but while looking through the list of GTSD events for the 13th, I noticed one that's somewhat unusual. It wasn't particularly energetic, but lasted for a lot longer than typical events for the region - it was determined to be coming from some supposedly seismically-stable region of New Mexico.
I don't think it's a nuclear bomb test, since the peak tailoff was far too slow. I'm wondering if it's some kind of mine cave-in, but I'm not aware of any mines that are large enough in that area. As far as I can tell, the area's part of a military range, so who know's what's going on there.
If you could look into it, I'd greatly appreciate it. Further charts and details are attached to this note - the event in question started at around 4pm.