- © 2015 by the Seismological Society of America
Online Material: Location uncertainty estimation; figures of waveform comparison, location maps, and Pg/Lg spectral ratios; tables of earthquake parameters and Lg‐wave amplitude ratios.
Three nuclear tests (in 2006, 2009, and 2013) conducted by the Democratic People’s Republic of Korea (North Korea) are all detected and confirmed by many governmental and international agencies (e.g., the U. S. Geological Survey [USGS] and the Comprehensive Nuclear‐Test‐Ban Treaty Organization [CTBTO]). The locations and yields of these tests have also been extensively studied by many research groups (e.g., Richards and Kim, 2007; Koper et al., 2008; Zhao et al., 2008, 2012, 2014; Murphy et al., 2010; Wen and Long, 2010; Chun et al., 2011; Zhang and Wen, 2013). However, it is under intensive debate among the governmental agencies and research groups whether North Korea has conducted other small nuclear tests. In particular, De Geer (2012) reported the detection of xenon and xenon daughter radionuclides between 13 and 23 May 2010 in four atmospheric radionuclide surveillance stations, located in South Korea, Japan, and the Russian Federation. He suggested the presence of barium‐140 can be explained only by a sudden nuclear event, with the corresponding trinitrotoluene equivalent in a range of 50–200 t and the estimated time‐zero at 6:00+18 hr/−30 hr UTC on 11 May 2010 (De Geer, 2012; see also Brumfiel, 2012). The fissile material of the possible mid‐May 2010 nuclear test is indicated as uranium‐235 rather than the plutonium‐239 inferred from the radioxenon signal detected at Geojin in South Korea (De Geer, 2012, 2013), although Wright (2013) suggested they cannot be clearly discriminated …