FIELD GEOMETRY

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Introduction to Seismic Reflection Imaging Pt 2
FIELD GEOMETRY FOR MULTICHANNEL SEISMIC (MCS)
PROFILES
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• Layouts for
• a comon-shot gather
• a cmmon mid-point gather and
• a common receiver gather.

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Sequence of survey layouts to acquire a 6-fold
coverage S indicates the source and G a geophone
(or hydrophone).
Fold N/2n where N total number of receiver
groups n number of group intervals moved
between shots
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Results of common mid-point (CMP) stacks showing
improvement in imaging for summations of 6, 18
and 48 shot-receiver pairs.
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• Composite shallow reflection record made up of
  five separate 12-channel records, each of which
  was recorded with a different time delay between
  the shot instant and the start of recording.
• Corresponding time-distance graph identifying the
  major seismic events on the record. The optimum
  window is that range of source-receiver
  separations that allows the target reflection to
  be observed without interference from other
  events.

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Example of a common mid-point gather
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Some Examples of Shot Gathers
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The application of a time-varying gain function
to a waveform exhibiting spherical divergence, in
order to recover signal amplitudes at later
travel times. Gain functions are applied in
discrete windows(labelled 1 to 5 as shown).
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Types of filters (A) bandpass (B) low-cut
(high-pass) (C) high-cut (low-pass) (D) notch.
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