Surface And Borehole Seismic Characterization Of The Boise Hydrogeophysical Research Site

We conducted borehole to borehole, borehole to surface, and surface seismic experiments<br>to optimize data acquisition parameters, obtain a seismic velocity model, and to characterize seismic<br>stratigraphic units in a shallow aquifer at the Boise Hydrogeophysical Research Site. The<br>aquifer consists of coarse (cobble-and-sand) fluvial deposits underlain by clay at 18-2 1.5 m depth.<br>We acquired data with a downhole seismic source (sparker), a sledge hammer source, a hydrophone<br>string, a borehole geophone, and a surface geophone array to compare seismic signal quality<br>and to place limitations on each seismic method. To fully characterize seismic reflections, the<br>source-receiver geometry is an important parameter for both borehole and surface experiments.<br>Direct arrivals and the presence of seismic reflections suggest a correlation between porosity<br>changes and seismic velocities at the site. We have defined four seismic stratigraphic horizons<br>that correlate with surface and borehole ground penetrating radar results, geophysical logs, and<br>lithologic logs. These results provide an initial framework for hydrologic modeling.