Advanced Seismic Analyses of the Source Characteristics of the 2006 and 2009 North Korean Nuclear Tests

Murphy, John; Stevens, J. L.; Kohl, Benjamin C.; Bennett, Theron J.

doi:10.1785/0120120194

Cited by 48 publications

(39 citation statements)

References 37 publications

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“…We seek to locate the 2006 event using all available time-delay measurements relative to each of the other three events. We selected many diverse subsets of the total number of available phases for each calculation: a procedure with similarities to the jack-knife (remove one station at a time) method employed by Murphy et al (2013).…”

Section: The North Korean Nuclear Tests 15mentioning

confidence: 99%

“…Given three pairs of events, there is now considerable redundancy in the data with far more observations available than are strictly necessary to perform a relative event location. (This data redundancy was exploited by Murphy et al 2013, who performed a jack-knife procedure to obtain a set of relative event location estimates that were less dependent upon individual measurements.) By carefully selecting subsets of observations (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Accurate relative location estimates for the North Korean nuclear tests using empirical slowness corrections

Gibbons¹,

Pabian

Näsholm³

et al. 2016

Geophys. J. Int.

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SUMMARYDeclared North Korean nuclear tests in 2006, 2009, 2013, and 2016 were observed seismically at regional and teleseismic distances. Waveform similarity allows the events to be located relatively with far greater accuracy than the absolute locations can be determined from seismic data alone. There is now significant redundancy in the data given the large number of regional and teleseismic stations that have recorded multiple events, and relative location estimates can be confirmed independently by performing calculations on many mutually exclusive sets of measurements. Using a 1-dimensional global velocity model, the distances between the events estimated using teleseismic P phases are found to be approximately 25% shorter than the distances between events estimated using regional Pn phases. The 2009The , 2013, and 2016 events all take place within 1 km of each other and the discrepancy between the regional and teleseismic relative location estimates is no more than about 150 m. The discrepancy is much more significant when estimating the location of the more distant 2006 event relative to the later explosions with regional and teleseismic estimates varying by many hundreds of meters. The relative location of the 2006 event is challenging given the smaller number of observing stations, the lower signal-to-noise ratio, and significant waveform dissimilarity at some regional 2 S. J. Gibbons et al.stations. The 2006 event is however highly significant in constraining the absolute locations in the terrain at the Punggye-ri test-site in relation to observed surface infrastructure.For each seismic arrival used to estimate the relative locations, we define a slowness scaling factor which multiplies the gradient of seismic traveltime versus distance, evaluated at the source, relative to the applied 1-d velocity model. A procedure for estimating correction terms which reduce the double-difference time residual vector norms is presented together with a discussion of the associated uncertainty. The modified velocity gradients reduce the residuals, the relative location uncertainties, and the sensitivity to the combination of stations used. The traveltime gradients appear to be overestimated for the regional phases, and teleseismic relative location estimates are likely to be more accurate despite an apparent lower precision. Calibrations for regional phases are essential given that smaller magnitude events are likely not to be recorded teleseismically. We discuss

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Section: The North Korean Nuclear Tests 15mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Accurate relative location estimates for the North Korean nuclear tests using empirical slowness corrections

Gibbons¹,

Pabian

Näsholm³

et al. 2016

Geophys. J. Int.

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“…The observations of the Love waves generated by nuclear explosions point to their radially asymmetric nonisotropic radiation and have been reported by many authors, e.g., for the Nevada Test Site explosions [ Aki et al ., ; Toksöz et al ., ; Aki and Tsai , ; Wallace et al , , ], for the explosions in Eastern Kazakhstan [ Helle and Rygg , ], in China [ Zhang , ], and also in North Korea [ Ford et al ., ; Murphy et al ., ; Barth , ]. The excitation of Love waves (and SH waves) has been mostly attributed to tectonic stress release produced either by a triggered tectonic earthquake on a nearby fault [ Archambeau , ] or by stress relaxation of the highly fractured zone immediately around the detonation point [ Archambeau , ; Harkrider , ; Minster and Suteau , ].…”

Section: Origin Of the Nonisotropic Radiationmentioning

confidence: 99%

Nonisotropic radiation of the 2013 North Korean nuclear explosion

Vavryčuk

Kim²

2014

Geophysical Research Letters

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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.

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“…From a consideration of topography, M13's locations are implausible in relation to all adits known at the time these tests took place, because they would require valley traverses away from the mountains in which the tunnel portals are located. Pabian and Hecker (2012) synthesized consistent aspects of the 2006-2009 relative locations obtained by Murphy et al (2010Murphy et al ( , 2011 and Wen and Long (2010). Their absolute geopositioning results were derived explicitly through a confluence of several constraining factors.…”

Section: Introductionmentioning

confidence: 68%

“…An Alternative Approach to Improve Geopositioning of DPRK Tests M13 (as well as Murphy et al, 2010Murphy et al, , 2011) associate a single-tunnel portal, commonly referred to by other researchers (and the media) as the west portal with both the 2006 and the 2009 DPRK nuclear tests. We believe there is sufficient evidence to conclude that the two events were supported by separate tunnels, each accessed via different portals, with each tunnel projecting directly into the adjacent mountain/ ridgeline for approximately 1 km in a direction of maximum relief, precisely as M13 surmised on page 1651 but subsequently discounted.…”

Section: Introductionmentioning

confidence: 99%

Comment on "Advanced Seismic Analyses of the Source Characteristics of the 2006 and 2009 North Korean Nuclear Tests" by J. R. Murphy, J. L. Stevens, B. C. Kohl, and T. J. Bennett

Patton

Pabian

2014

Bulletin of the Seismological Society of America

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Advanced Seismic Analyses of the Source Characteristics of the 2006 and 2009 North Korean Nuclear Tests

Cited by 48 publications

References 37 publications

Accurate relative location estimates for the North Korean nuclear tests using empirical slowness corrections

Accurate relative location estimates for the North Korean nuclear tests using empirical slowness corrections

Nonisotropic radiation of the 2013 North Korean nuclear explosion

Comment on "Advanced Seismic Analyses of the Source Characteristics of the 2006 and 2009 North Korean Nuclear Tests" by J. R. Murphy, J. L. Stevens, B. C. Kohl, and T. J. Bennett

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