Block Motion Estimates from Seismological Observations of MIGHTY EPIC and DIABLO HAWK

摘要

Seismological observations of the underground explosions MIGHTY EPIC and DIABLO HAWK were used to infer the extent of the block motions associated with these events. The data were three-component velocity recordings from the nine station seismic network operated by Lawrence Livermore Laboratory (LLL) and Sandia Laboratories at ranges from 131 to 368 km. Five additional stations were fielded by Systems, Science and Software (S3) for DIABLO HAWK. The two events were first compared by cross-spectral analysis of common recordings. A key conclusion of this analysis is that the long period waves generated by MIGHTY EPIC were about 75 percent larger than for DIABLO HAWK while the short period source levels differed by about 15 percent. This difference was observed on almost all common recordings. The events were individually analyzed using a narrow-band filter program to identify the long period fundamental mode Love and Rayleigh waves. The source was then assumed to consist of a spherically symmetric explosion and the block motion generated double-couple. For DIABLO HAWK the amplitudes of the six second Love, Rayleigh and Love/Rayleigh ratio were fit by a solution with faulting oriented N16 degrees E and a seismic moment of 1.3 x 10 to the 21st power dyne-cm.