The USGS does maintain a catalog for other event types that are explosions - they currently list accidental, chemical, experimental, explosions, industrial, mining, nuclear and volcanic. I have used volcanic and know that there is at least some nuclear data.
I think that the existing seismic stations for published earthquake catalogue may have catched the explosion tremors. However, the data analysis and validation may play a role.
I know that at CTBTO in Vienna they are working on the field of nuclear explosions. An alternate source might be the "Oklahoma geological Survey Observatory - Catalog of Nuclear Explosions". You might also consider to search for the key word "forensic seismology". Good luck!