VSP (Vertical Seismic Profile) site characterization at NTS (Nevada Test Site)

In late 1989 a site characterization study using the Vertical Seismic Profile (VSP) method was conducted as part of the On Site Seismic Yield (OSSY) experiment organized by Lawrence Livermore Laboratory as well UE-10 ITS {number sign}3 located in Yucca valley inside the Nevada Test Site (NTS). The OSSY experiment fired 10 and 100 lb explosive sources at several depths in the hole, with multiple 3-component receivers on the surface, to test the nature of seismic signal scaling with source size and the accuracy in the near field of source modeling algorithms. Shear-waves in particular are influenced strongly by both the source mechanism and the properties of the propagation path. The multi-component OSSY VSP (3-component receivers at several depths, with P, SV and SH surface sources) measured the seismic wave transmission separately for three source types. The VSP surface-source to borehole-receiver acquisition geometry was reversed in the subsequent explosion phase of the experiment in which the explosion-generated waves presumably experienced the same propagation effects as did the waves generated by the VSP sources. The OSSY VSP has progressed through data acquisition and processing to an initial interpretation in terms of P- and S-velocity structures. Preliminary result were presented at themore » 1990 meeting of the Seismological Society of America (Daley and McEvilly, 1990). This report is an overview of the data acquisition, processing and analysis to date, and on plans for the next of interpretation. 6 refs., 23 figs.« less