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 2 Wave interaction with boundaries
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(T.M. Boyd at CSM)
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(T.M. Boyd at CSM)
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(T.M. Boyd at CSM)
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(T.M. Boyd at CSM)
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(T.M. Boyd at CSM)
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(T.M. Boyd at CSM)
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(T.M. Boyd at CSM)
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(T.M. Boyd at CSM)
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(T.M. Boyd at CSM)
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(T.M. Boyd at CSM)
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(T.M. Boyd at CSM)
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(T.M. Boyd at CSM)
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Multiple-exposure snapshot showing propagation
sequence of first arrival energy for a cross
section.
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(T.M. Boyd at CSM)
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(T.M. Boyd at CSM)
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Schematic of Snells Law showing both ray paths
and wavefronts for a simple, pre-critical
velocity model.
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Snells Law for incident P-waves and S-waves
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Fermats Least-Time Principle
A light ray traveling from one point to another
will follow a path such that, compared with
nearby paths, the time required is either a
minimum or a maximum or will remain unchanged
(it the ray will remain stationary).
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Using Fermats Least-Time Principle to
demonstrate the correctness of Snells Law.
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(T.M. Boyd at CSM)
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(T.M. Boyd at CSM)
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(T.M. Boyd at CSM)
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Demonstration of the normal incident reflection
and transmission coefficients across a boundary
of acoustic impedance change.
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Demonstration of the transmission and reflection
coefficients for models having a velocity
contrast or a density contrast.
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Is this right???
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For transmission loss, the return amplitude is a
function of all of the interfaces along the ray
path and accounts for the sign.
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First Fresnel zone defined by the upper part of
figure (A) frequency variability of Fresnel
zones indicated by lower part (B).
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Schematic of first Fresnel Zone showing spherical
wavefront of seismic wave impinging on acoustic
impedance boundary.
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Nomogram for determining first Fresnel zone
radius.
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Lateral resolution issues surrounding Fresnel
Zones.
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Snapshot of propagating wave time t later after a
plane wave hit the corner of the semi-infinate
barrier shown.
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Seismogram of three different infinite boundary
terminations note diffraction curvature
decreases with time (depth).
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Concept of wavefront healing
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Example showing point diffractor becoming wider
until it is a ubiquitous reflector note
amplitude of constructively interfering point
diffractions.
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Certain multiple bounce reflections with very
short paths modify the effective signature of the
seismic wavelet.
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The Zoeppritz Equations predict P converting to S
at boundary
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Acoustic 2-D wave-equation modeling with MIDAS
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Elastic 2-D wave-equation modeling with MIDAS Z
component
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Elastic 2-D wave-equation modeling with MIDAS X
component
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