Analysis of the Seismic Source Characteristics of Explosions in Low- Coupling Dry Porous Media

摘要

Over the past two years we have been analyzing P wave seismic source coupling characteristics of underground nuclear explosions in dry, porous media. The technical objectives of this research have been to develop a Mueller/Murphy frequency dependent analytic seismic source model for explosions in such media and to apply the model to quantitative assessments of seismic detection, identification and yield estimation capabilities relevant in nuclear test monitoring. Broadband seismic data recorded at the Lawrence Livermore National Laboratory (LLNL) regional network stations from 63 nuclear explosions conducted above the water table at the Yucca Flat testing area of the Nevada Test Site (NTS) were analyzed and compared to observations and models for explosions in good coupling media below the water table. The results of these analyses indicate that the P wave seismic source functions for underground nuclear explosions in dry, porous media can be well-approximated by simply dividing the P wave source functions for the same explosions in saturated tuff, predicted by the validated Mueller/Murphy source model, by a frequency independent gas-filled porosity (Gp) reduction factor (RF) given by RF = 1.75 * 100.024Gp.