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Curved Reflectors - Seismology - Lecture Slides, Slides of Geology

Following are the Fundamentals of these Lecture Slides : Curved Reflectors, Reflector, Vertical Ray, Curvature, Surface, Common, Multiple Arrivals, Synclines, Bow Tie, Narrowed Syncline

Typology: Slides

2012/2013

Uploaded on 07/19/2013

saen.chumi
saen.chumi 🇮🇳

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Curved Reflectors
If the reflector is curved, distortions may be more
complex
There may be many paths between the reflector and receiver
The vertical ray is
generally not first to
arrive
Only true if the
center of curvature
is below surface of
earth
Common for tight
folds
Open folds don’t
usually produce
multiple arrivals
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Curved Reflectors

  • If the reflector is curved, distortions may be more complex - There may be many paths between the reflector and receiver
  • The vertical ray is generally not first to arrive - Only true if the center of curvature is below surface of earth - Common for tight folds - Open folds don’t usually produce multiple arrivals

Synclines

  • Raw data from a multi-shot reflection survey produce…
  • A “bow tie” pattern for synclines
  • If center of curvature is above the surface… - A narrowed syncline is produced

(stacked)

Migration

  • Migration: Correcting for the displacement of position and the shape of a non-horizontal reflector - Also includes several other geometric corrections - So, the previous examples were examples of migration!
  • Extremely complicated process
    • This is the main reason why ~30% of the world’s CPU time is spent on seismic reflection
    • Requires sophisticated numerical routines to detect and correct these patterns.
    • Sometimes reflection profiles are left “unmigrated”
      • Saves time and money
      • Reflection seismology experts can look at unmigrated sections and immediately see the migrated image in their head.

Diffraction

  • Although many reflectors are laterally continuous, often discontinuous reflectors are encountered - Discontinuous reflectors produce diffracted waves - Remember Huygen’s Wavelets? - Three main causes of diffraction… - Faulted rock layers - Pinchouts (a stratigraphic layer that thins to nothing) - Point sources (usually non-geologic)

Migration also corrects these artifacts!