Infrasound observation of the apparent North Korean nuclear test of 25 May 2009

Abstract

, a seismic event (m b 4.6) was recorded from a source in northeastern North Korea, close to the location of a previous seismic event on 9 October 2006. Both events have been declared to be nuclear tests by North Korea. For the more recent test, five seismo-acoustic arrays in South Korea recorded epicentral infrasonic signals. The signals are characterized by amplitudes from 0.16 to 0.35 microbar and dominant frequencies between 0.8 and 4.3 Hz. Celerities determined for the arrivals suggest that most of the infrasonic energy travelled as a stratospheric phase. Based on observed stratospheric amplitudes, the epicentral infrasonic energy was estimated to be equivalent to that expected from 3.0 tons of high explosives detonated on the surface. We conclude that this small energy estimate is due to the atmospheric coupling from the strong surface ground motion rather than the direct transfer of explosion energy to the air. This relatively small infrasonic to seismic energy ratio could be used to distinguish the event from a common surface explosion.

Ionospheric detection of the 25 May 2009 North Korean underground nuclear test

“…Indeed, the radionuclide network apparently did not find evidence of the 25 May 2009 underground nuclear explosion (UNE) carried out by North Korea (i.e., the Democratic People's Republic of Korea). Thus, independent scientific evidence for the several‐kiloton estimated UNE was restricted primarily to its seismic signature and possibly epicentral infrasonic signals that may have been recorded at five of the seven operating seismo‐acoustic arrays in South Korea [ Che et al , 2009].…”

Geomagnetic conjugate observations of ionospheric disturbances in response to a North Korean underground nuclear explosion on 3 September 2017

“…The effects of a UNE on the ionosphere could be very similar to that of earthquakes on the ionosphere. In previous studies, AGWs are regarded as the most likely mechanism for atmospheric and ionospheric disturbances excited by a UNE or earthquakes (Mikhailov et al, 2000;Che et al, 2009;Garrison et al, 2010;Park et al, 2011Park et al, , 2013Yang et al, 2012;Maruyama et al, 2016). Klimenko et al (2011) proposed that the ionospheric disturbances were generated by small-scale internal gravity waves (IGWs) through propagation and dissipation processes during seismic activity.…”

Experimental characterization of seasonal variations in infrasonic traveltimes on the Korean Peninsula with implications for infrasound event location

“…2004). ULDAR consists of seven acoustic sensors and five seismometers located on an island in the ocean, to enhance azimuth coverage of previous array distributions and to supply infrasound data recorded in an oceanic environment (Che et al . 2009).…”

“…CHNAR consists of 11 acoustic sensors and four seismometers that were deployed by Korea Institute of Geoscience and Mineral Resources (KIGAM), in collaboration with Southern Methodist University with the goal of detecting distant infrasound signals from natural and anthropogenic phenomena in and around the Korean Peninsula (Stump et al 2004). ULDAR consists of seven acoustic sensors and five seismometers located on an island in the ocean, to enhance azimuth coverage of previous array distributions and to supply infrasound data recorded in an oceanic environment (Che et al 2009). Acoustic sensor layouts are shown in Fig.…”