Revised Geologic Site Characterization of the North Korean Test Site at Punggye-ri

Coblentz, David; Pabian, Frank

doi:10.1080/08929882.2015.1039343

Cited by 32 publications

(20 citation statements)

References 7 publications

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“…The locations relative to each other are constrained to within an uncertainty of at most a few hundred meters and this provides significant constraints as to where the tests could have been carried out at Punggye-ri (see e.g. Coblentz & Pabian 2015).…”

Section: The North Korean Nuclear Tests 15mentioning

confidence: 99%

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

Gibbons¹,

Pabian²,

Näsholm³

et al. 2017

Preprint

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Declared 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-D global velocity model, the distances between the events estimated using teleseismic P phases are found to be approximately 25 per cent shorter than the distances between events estimated using regional Pn phases. The 2009, 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 metres. 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 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 the implications for the absolute event locations. Placing the 2006 event under a local maximum of overburden at 41.293°N, 129.105°E would imply a location of 41.299°N, 129.075°E for the January 2016 event, providing almost optimal overburden for the later four events.

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Section: The North Korean Nuclear Tests 15mentioning

confidence: 99%

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

Gibbons¹,

Pabian²,

Näsholm³

et al. 2017

Preprint

Self Cite

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“…The location of the tunnel entrances for the eastern and western tunnels are within the white boxes. Estimates of tunnel entrance locations and elevations are from Coblentz and Pabian (). The distance from the center of the NK1 probability ellipse to that for NK3 is 2.57 km.…”

Section: Introductionmentioning

confidence: 99%

“…), as these affect the cavity size, seismic coupling, and yield scaling, along with the elastic structure and attenuation properties of the crust and upper mantle along each path from the source to recording stations. Synthesizing existing small‐scale geologic maps with topographic information, specifically the pattern of drainages within the region, Coblentz and Pabian () conclude that Mount Mantap is composed of either a Mesozoic/Cretaceous diorite or a Mesozoic granite and overlain by stratified volcanics and a thin basalt cap layer. The site of the 2006 event, ~2 km to the east, differs in that the rock in this region is likely highly fractured and near the eastward extent of a granite‐gneiss contact (Coblentz & Pabian, ).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2019

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The yields of the six declared underground nuclear tests at the North Korean test site are estimated using high-frequency teleseismic P wave amplitude modeling and waveform equalization of short-period teleseismic P waves and regional Pn signals. Average amplitudes of the first cycle of high-frequency (>4 Hz) filtered P wave displacements for each event, adjusted for station sampling relative to the 3 September 2017 event, are modeled using Mueller-Murphy explosion source models for granite and a constant-Q attenuation operator with t* = 0.78 ± 0.03 s. The yield estimates range from 2.6 to 230 kt. Intercorrelation, a waveform equalization procedure that accounts for source function and depth-phase variations between events, is applied to large sets of filtered (>0.8 Hz) teleseismic P and regional Pn seismograms. Searching over yield and burial depth for both events gives optimal parameters by simultaneous waveform equalization of multiple stations. Using specified burial depths spanning from 430 to 710 m for all events based on estimated locations in the source topography assuming tunneling with 4% grade, along with allowing for reduction in source region velocity due to weathering, rock layering, and damage zones, gives yield estimates ranging from 1.4 to 250 kt. Comparison of predicted and observed spectral ratios of Pn phases at station MDJ establishes that these source models are reasonable. Using the preferred yield estimates from intercorrelation, W IC , a yield-calibrated relation of m bNEIC = 0.9 log 10 W IC + 4.13 is determined for the North Korean test site.

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Section: The North Korean Nuclear Tests 15mentioning

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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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

show abstract

Revised Geologic Site Characterization of the North Korean Test Site at Punggye-ri

Cited by 32 publications

References 7 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

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

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

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