Nonisotropic radiation of the 2013 North Korean nuclear explosion

Abstract

On 12 February 2013, North Korea conducted an underground nuclear test in the northeastern mountainous part of the country. The explosion reached magnitude m b = 5.1 being recorded at most of seismic stations around the world and becoming one of the best ever recorded nuclear explosions in history. Similarly, as other nuclear explosions buried in Nevada, Kazakhstan, or China, the 2013 North Korean explosion is characterized by a significant nonisotropic radiation. This radiation is manifested by distinct SH and Love waves in the wave field and is inconsistent with the model of a spherically symmetric source. We show that the Love waves are not generated by a tectonic earthquake triggered on a nearby fault structures but produced by asymmetry of the explosive source caused by presence of deviatoric stress in the surrounding rock. The retrieved moment tensor of the 2013 explosion is characterized by the isotropic component of 57 ± 5%, the double-couple component of 17 ± 9%, and the compensated linear vector dipole component of 24 ± 7%. The P, T, and N axes of the moment tensor are consistent with the principal axes of the regional tectonic stress in the Korean Peninsula. A comparison of waveforms and particle motions of the 2013 explosion and the previous North Korean nuclear explosion buried in 2009 indicates that the 2013 explosion was slightly more nonisotropic.

Generalized Source Model of the North Korea Tests 2009–2017

“…S4). Our P-T axes are close to the 2013 test studied by Vavryčuk and Kim (2014), who claimed agreement of the P axis with the principal regional compression, whereas the almost vertical T axis was less easily explainable.…”

Yield Estimates for the Six North Korean Nuclear Tests From TeleseismicPWave Modeling and Intercorrelation ofPandPnRecordings

“…A variety of methods have been used to estimate the yields or seismic moments of the six tests, including assumed transportability of body wave, surface wave, or Lg magnitude yield scaling relations (e.g., Chun et al, ; Hartmann et al, ; Yao et al, ; Zhang & Wen, ; Zhao et al, , , , , Zhao, Xie, Wang, et al, ,Zhao, Xie, He, et al, ); modeling of surface deformation (Wang et al, ; Wei, ), regional waveforms and spectra (e.g., Murphy et al, ; Rougier et al, ; Stevens & O'Brien, ; Stroujkova, ; Wang et al, ), regional coda envelopes (e.g., Pasyanos & Myers, ), network‐averaged teleseismic P wave spectra (e.g., Murphy et al, ), and teleseismic P waveforms (e.g., Chaves et al, ; Ni et al, ); and moment tensor inversion for the total and isotropic moment of the explosions (e.g., Alvizuri & Tape, ; Barth, ; Cesca et al, ; Chiang et al, ; Ford et al, ; Ichinose et al, ; Liu, Li, Zahradnik, Sokos, Liu, et al, ,Liu, Li, Zahradník, Sokos, & Plicka, ; Vavrycuk & Kim, ; Wang et al, ; Yao et al, ). Some depth constraints are inferred from infrasound as well (Assink et al, ).…”

North Korea's 2017 Test and its Nontectonic Aftershock

“…The full moment tensor (MT) inversion of the 2009 test revealed a nondouble‐couple source (e.g., Ford et al, ). Nonisotropic radiation, including shear motion, was observed in the 2013 test (Barth, ; Vavryčuk & Kim, ). The 2016 tests helped to delimit a significant uncertainty in the source parameters (Cesca et al, ).…”