L19_SeismicRefractionII-page8

L19_SeismicRefractionII-page8 - One at center: to determine...

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Applied Geophysics – Refraction II Experiment design Geophones : often use the same geophones as in reflection work – constraint is the frequency of the geophones Frequency : refraction studies may be constrained to lower frequencies due to longer ray lengths (10Hz vs. 100Hz for reflection) Profile length : typically 5 to 10 times the depth of the refractor to ensure head wave as first arrival Shot points : Typically five for each geophone array • One at each end: uppermost velocity plus reversed line
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Unformatted text preview: One at center: to determine uppermost layer velocity Two long offset shots: to determine phantom arrivals and reverse line Applied Geophysics Refraction II Low velocity layers Limitations They are completely invisible to the refraction method They will cause miss-interpretation of the depth of lower lying layers Lower layers appear deeper than they are The intercept of the refraction from layer 3 will be dependent on the thickness and velocity in layer 2...
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This note was uploaded on 01/07/2012 for the course PHYSICS 384 taught by Professor Wei during the Spring '09 term at SUNY Stony Brook.

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