Earthquakes near Kaktovik Alaska are depth=0km or very shallow (3km deep). I can't find any info on a DUMB there but there used to be a USAF DEW base on Barter Island near Kaktovik. The waveforms show (initial impact) BOOM, then shaking. Not sure if it's an explosion or volcanic activity, but there is an oil pipeline about 130m SW. There have been about 40 magnitude 2.5+ earthquakes in this area in the last week including a 6.4.
forgot other screen pix
First waveform confirms concentrated blast of some sort (like a gunshot/no echo), the waveforms following are the shaking that happens.
Aftershocks are usually underground