Refraction blind spot
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| Series | Geophysical References Series |
|---|---|
| Title | Problems in Exploration Seismology and their Solutions |
| Author | Lloyd P. Geldart and Robert E. Sheriff |
| Chapter | 11 |
| Pages | 415 - 468 |
| DOI | http://dx.doi.org/10.1190/1.9781560801733 |
| ISBN | ISBN 9781560801153 |
| Store | SEG Online Store |
Problem 11.16
In early refraction exploration for salt domes, a “blind spot” (the region B–A in Figure 11.16a(ii)) was found when the salt dome lay directly on the line between the source and the geophone, that is, arrivals were often too weak to detect. This was called absorption of the wave” by the salt dome. What is the true explanation of the absorption?
Solution
The vertical section in Figure 11.16a(i) shows rays being bent upon entering and leaving the salt dome. In the plan view of Figure 11.16a(ii), the bending of the rays in the horizontal plane is evident. This spreading of the wave, both vertically and horizontally, but especially the latter, lowers the energy density. Thus, the cause of the low amplitude is the raypath bending.
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| Feasibility of mapping a horizon using head waves | Interpreting marine refraction data |
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| Geologic interpretation of reflection data | 3D methods |
Also in this chapter
- Salt lead time as a function of depth
- Effect of assumptions on refraction interpretation
- Effect of a hidden layer
- Proof of the ABC refraction equation
- Adachi’s method
- Refraction interpretation by stripping
- Proof of a generalized reciprocal method relation
- Delay time
- Barry’s delay-time refraction interpretation method
- Parallelism of half-intercept and delay-time curves
- Wyrobek’s refraction interpretation method
- Properties of a coincident-time curve
- Interpretation by the plus-minus method
- Comparison of refraction interpretation methods
- Feasibility of mapping a horizon using head waves
- Refraction blind spot
- Interpreting marine refraction data
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