| Abstrakt: |
The yields of the six declared underground nuclear tests at the North Korean test site are estimated using high‐frequency teleseismic Pwave amplitude modeling and waveform equalization of short‐period teleseismic Pwaves and regional Pnsignals. Average amplitudes of the first cycle of high‐frequency (>4 Hz) filtered Pwave 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‐Qattenuation 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 Pand regional Pnseismograms. 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 Pnphases at station MDJ establishes that these source models are reasonable. Using the preferred yield estimates from intercorrelation, WIC, a yield‐calibrated relation of mbNEIC= 0.9 log10WIC+ 4.13 is determined for the North Korean test site. Yields of six North Korean underground nuclear tests are estimated by modeling high‐frequency (>4 Hz) teleseismic Pwave amplitudesWaveform equalization of short‐period teleseismic Pand regional Pnseismograms provides yield and depth estimates for all six eventsSpectral ratios of broadband regional Pnsignals at station MDJ validate the six explosion source models from waveform equalization |
Plný text