ESCI 444Exploration Geophysics II Reflection Seismic Data Processing

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ESCI 444-Exploration Geophysics IIReflection
Seismic Data Processing
Spring, 2007

• Steve H. Danbom, Ph.D., P.G.
• Adjunct Professor
• Office - Room 206A
• Office Hours By Appointment

Lecture Week 3 The seismic refraction method
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(T.M. Boyd at CSM)
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Seismic time-distance curves from the geological
model shown for both reflection and refraction
events.
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Multiple-exposure snapshot showing propagation
sequence of first arrival energy for a cross
section.
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Travel path for ray that is the first possible
totally refracted signal no energy is
transmitted into media 2 beyond incident angle ic.
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Derivation of the equation that describes the
time-distance relationship of the critically
refracted head wave.
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Another form of equation that describes the
time-distance relationship of the critically
refracted head wave.
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Travel path for ray that is the first possible
totally refracted signal for two layers on a half
space.
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Generalization of the equations that describe the
time-distance relationship of the critically
refracted head wave.
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(T.M. Boyd at CSM)
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Schematic with algebra and geometry to discuss
the refraction equation for a single layer on a
half-space with no dip.
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Here is one of the reasons early oil-prospecting
geophysicists were not completely satisfied with
the seismic refraction method.
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Schematic showing multiple-exposure first
arrivals and the resulting time-distance graphs.
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As opposed to a layered-earth concept, diving
rays are the consequence of velocity gradients
within the earth.
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Heres an example of a low-velocity layer
creating a zone on the surface for which
reception of these turning rays is impossible.
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or perhaps this is the earth model???
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REFRACTION TIME DATA
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SEISMIC REFRACTION
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Figure 31 -- Geometrics SmartSeis P-wave file for
Line 1 showing picks -- Shot point at 244 feet
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Figure 32 -- Geometrics SmartSeis P-wave file for
Line 1 showing picks (zoomed image) -- Shot point
at 244 feet
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Figure 33 -- Line 1 P-wave refraction traveltime
data showing the 7 field files used in the
construction of Figure 34.
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West
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East
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East
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West
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West
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