After noting the locations on the map, I'm going to venture to say it'd be not feasible whatsoever to have any kind of base buried 6 miles deep directly on a fault line. There are faults every where all of the Earth, many even across just the USA. There'd be such extreme heat and variability in terms of movement and pressure that any "base" would be crushed, or at least a thin little access elevator (down 6 miles in length...) would be quickly made inaccessible by the processes of the Earth. I want to believe in DUMBs and that good guys are destroying them but in no way is an epicenter marked that deep on a fault line evidence of a base.

Also data filters could just be the result of estimation and programming. There may be a higher priority to label a weak signal at over 10km, pending certain factors. I highly doubt underground resolution at that depth is very good anyway. I've studied and have first hand experience doing some seismic surveys and even shallow depth seismic isn't quite the resolution you think it'd be. I could be all wrong and underestimate the power and complexity of the sensors being used here, but my analysis warns that you're putting too much faith in all of that data being correct to begin with.

After noting the locations on the map, I'm going to venture to say it'd be not feasible whatsoever to have any kind of base buried 6 miles deep directly on a fault line. There are faults every where all of the Earth, many even across just the USA. There'd be such extreme heat and variability in terms of movement and pressure that any "base" would be crushed, or at least a thin little access elevator (down 6 miles in length...) would be quickly made inaccessible by the processes of the Earth. I want to believe in DUMBs and that good guys are destroying them but in no way is an epicenter marked that deep on a fault line evidence of a base.