GEOPHYSICAL STUDIES SITE B GEOPHYSICAL STUDIES PROGRESS OSPER PROJECT SITE B BRUCE SMITH ROBERT BISDORF RAY HUTTON MARK TABACHECK ROBERT HORTON

GEOPHYSICAL METHODS USED DC RESISTIVITY SOUNDING obtain variation in electrical resistivity as a function of depth (to about 40 meters) ELECTROMAGNETIC PROFILING (EM31) obtain variation in electrical conductivity as a function of position (mapping lateral variations) 3 to 6 meters TOTAL FIELD MAGNETICS (not discussed) geologic mapping detect magnetic metallic objects (oil field pipes etc.) ELECTROMAGNETIC PROFILE (EM34…not discussed) depth to 40m but very noisy due to metallic pipes

DC RESISTIVITY

B SITE LOCATION DC RESISTIVITY SOUNDINGS

DC SOUNDINGS SITE B

ELECTRICAL CROSS SECTION SITE B RESISTIVITY (ohm meters) CONDUCTIVITY (millisiemens) ρ = 1000/σ(ms) σ(ms) = 1000/ρ 100 ohm meters = 10 ms

RESISTIVITY SOUNDING SITE B CONDUCTIVITY WEATHERED BEDROCK

EM31 CONDUCTIVITY SURVEY Vertical dipoles depth ~4.5m Horizontal dipoles depth ~2.25m

EM31 HMD 2.25m depth map

EM31 VMD 4m depth map

EM31 HMD 4m 1960 Photo