Acquisiton of Passive Seismic Data at Tooele Army Depot, Utah David Sheley, Travis Crosby, Jianming Sheng

Survey Location North 1 Mile

Survey Location

Geophones Hz 2 m intervals 48 8-Hz groups 2 m intervals 6 geophones/group 2 m array length

Source: Hammer Drill Source Period = 0.7 sec = 0.7 sec Source Depth = 60 m = 60 m Target Depth (Bedrock) (Bedrock) = 140 m = 140 m

Seismographs

Recording Parameters 40-Hz Geopones 8-Hz Geophone Groups dt = 2 ms 5000 samples 31,000 samples 10 sec record 64 sec record 4 Hz low cut 250 Hz high cut 130 m source horiz. offset 60 m source depth

Source Gathers 40-Hz Geopones 8-Hz Geophone Groups Traveltime (s) Offset (m) Traveltime (s) 096 Offset (m)

Source Gathers 40-Hz Geopones 8-Hz (20 – 250 Hz BP Filt) Traveltime (s) Offset (m) Traveltime (s) 096 Offset (m)

Conclusions & Future Work Hammer drill provides adequate energy at shallow depths to generate reflections.Hammer drill provides adequate energy at shallow depths to generate reflections. 40-Hz geophones attenuate surface wave energy.40-Hz geophones attenuate surface wave energy. Next: Crosscorrelate the data to image bedrock.Next: Crosscorrelate the data to image bedrock. 8-Hz geophone arrays need to be lengthened, but this will damage the signal.8-Hz geophone arrays need to be lengthened, but this will damage the signal.