1140 



Subsurface Geologic Methods 



PROBLEM 



METHOD 



RESULTS 



(10 A) 



BED ROCK DEPTH 



(lOB) 

 SEISMIC REFRACTION 



RECORDING 

 GEOPHONES^ TRUCK 



<^ 



■tr-TT^— ^ 



4 ^ i 



MEASURE VELOCITY OF SEISMIC 

 WAVES IN LAYERS 



(IOC) 

 CROSS-SECTIONS 



^SEISMIC DEPTH 

 POINTS 



(II A) 

 BURIED CHANNEL 



7 . I? 



COVERED I U- 





(lis) 

 SEISMIC REFRACTION 

 FAN SHOOTING 



^ 2 

 PLAN "" 



! 2 



'o ' ,.^ / ^ KNOWN 



/course of 



CHANNEL? 



(lie) 

 DETERMINE COURSE OF CHANNEL 



\''h°/nnW *", -"covered 

 / / 



/ / PLAN VIEW 



.SI / 



geophones 



ON AN ARC 



GRAVEL transmits SEISMIC 

 WAVES AT SLOWER SPEED 

 THAN SHALE 



4" / 



'EDGE OF 

 CHANNEL 



(12 A) 

 MAPPING SUB-DRIFT TOPOGRAPHY 



(I2B) 

 GRAVIMETER TRAVERSE 



.._._.J1_ 



MEASURE GRAVITY FORCE STATION 

 VALUES, RELATIVE TO A BASE, IN 

 I/IOO'S OF MILLI OYNES. 



(I2C) 

 GRAVITY FORCE CONTOURS 



fM 



CONTOUR LINES SHOW 

 SUB- DRIFT TOPOGRAPHY 



Figure 599. Seismic methods applied to engineering geology. 



