Analysis of Seismic P/S Ratios From Chemical Explosions at the Surface and Buried in Contrasting Geologies
Session: Explosion Seismology Applications and Advances [Poster]
Type: Poster
Date: 4/19/2021
Presentation Time: 11:30 AM Pacific
Description:
Historically, discrimination for large explosions, such as nuclear tests, from surrounding seismicity could be achieved on the basis of lower shear generation for explosive sources, particularly at higher frequencies, by using seismic P/S amplitude ratios. This method proved effective at many test sites and emplacement conditions around the world for explosions that could be recorded at regional distances (>200 km). Few studies exist that test this method for smaller events that may only be observed at local distances (<200 km), and results are mixed. Single-station ratios appear to be unreliable; while some stations show separation between explosion and earthquake populations, many do not. Network-averaging of P/S ratios may provide more consistent discrimination performance, however, more work is necessary to understand the reasons for success or failure of the P/S ratios at local distances.
Previous work has looked at the P/S discriminant at local distances using data from the Source Physics Experiment (SPE). Phase I of this experiment consisted of a series of chemical explosions in a single borehole located in granite. We extend our analysis here to include data from Phase II of SPE, a second series of explosions in a contrasting dry alluvium geology (DAG), as well as a series of surface explosions from the Large Surface Explosion Coupling Experiment (LSECE) at the same site. Preliminary results show no significant differences in the scatter of P/S ratios from the buried explosions in contrasting geologies or the surface explosions. Network-averaged ratios for the DAG explosions and the LSECE explosions show strong similarity, suggesting a similar scattering and conversion shear-wave generation for both buried and surface sources.
Presenting Author: Moira L. Pyle
Student Presenter: No
Authors
Moira Pyle Presenting Author Corresponding Author pyle4@llnl.gov Lawrence Livermore National Laboratory |
William Walter walter5@llnl.gov Lawrence Livermore National Laboratory |
|
|
|
|
|
|
|
Analysis of Seismic P/S Ratios From Chemical Explosions at the Surface and Buried in Contrasting Geologies
Category
Explosion Seismology Applications and Advances