According to a February 26 Global Security Newswire story, the recent North Korean nuclear test "brought fresh attention to the capabilities" of the CTBTO's monitoring system. The CTBTO's International Monitoring System (IMS) was able to detect the North Korean nuclear test within moments and forwarded information from its seismic and infrasound stations to state parties just over an hour after the explosion.
The IMS was also able to record the February 15 meteor explosion over the Ural Mountains in Siberia with 17 of its 45 infrasound stations. The IMS currently employs 274 certified stations around the globe, using a combination of seismic, infrasound, hydroacoustic, and radionuclide sensors to record nuclear test explosions.
For more information, view "Nuke Trial, Meteorite Highlight Test Ban Treaty Capabilities."
Also see "A Broader Reading of Seismic Waves from North Korea" by Jeffrey Park at the Bulletin of Atomic Scientists.