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SEISMIC REFRACTION SURVEY FOR ESTIMATING RIPPABILITY & DEPTH TO BEDROCK
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1480 ft/sec
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5020 ft/sec
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Refraction seismic surveys are conducted to determine the approximate depth to bedrock and to
provide compression wave velocity data that can be used for rippability guidance. Data is usually
collected along one or more spreads with each spread consisting of 24 geophones spaced 5 to 15
feet apart.
Depending upon which seismic processing program is used, source to geophone travel time data of
compression waves are converted to depth to bedrock values that can be displayed in a layer model
(top profile) or velocity model (lower profile) formats. A sledge hammer striking a metal plate can be
used for the source if the depth to bedrock lies less than 15 feet below surface. A Betsy shotgun or
an accelerated weight drop sources are recommended when anticipated depth to bedrock lies
beyond 15 feet.
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