1. Dipping layer reflection events and the common midpoint gather
Environmental and Exploration Geophysics II
Dipping layer reflection events and the common midpoint gather
tom.h.wilson
Department of Geology and Geography
West Virginia University
Morgantown, WV
Tom Wilson, Department of Geology and Geography

2. Objectives for the day
A shot record view of the dipping layer reflection
Analysis of the dipping layer reflection
The concept of normal moveout correction
The problem posed by dipping layers
Common midpoint sorting
Tom Wilson, Department of Geology and Geography

3. Dipping Layer Reflection Event with Offset Apex
Tom Wilson, Department of Geology and Geography

4. How do you find depth h, velocity V and dip ?
Tom Wilson, Department of Geology and Geography

5. If you could not see the direct arrival then you could solve for V using either expressions for t0 or tapex.
Tom Wilson, Department of Geology and Geography

6. Tom Wilson, Department of Geology and Geography

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9. Tom Wilson, Department of Geology and Geography

10. This is referred to as a stacking chart
This is referred to as a stacking chart. The significance of the name will become apparent later on.
Tom Wilson, Department of Geology and Geography

11. Bring questions to class on Tuesday
For next week at this time construct a stacking chart for a symmetrical split spread consisting of 12 geophones arranged 6 on each side of the source.
Bring questions to class on Tuesday
Tom Wilson, Department of Geology and Geography

12. Tom Wilson, Department of Geology and Geography

13. Tom Wilson, Department of Geology and Geography

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15. Tom Wilson, Department of Geology and Geography

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19. Tom Wilson, Department of Geology and Geography

20. The effect of the moveout correction on the traces in the common midpoint (CMP) gather is to create a composite normal incidence trace that effectively shares a coincident source and receiver at the midpoint shared by all the traces in the gather. We’ll discuss CMP data in more detail in a couple lectures.
Tom Wilson, Department of Geology and Geography

21. Homework
Construct a stacking chart for a symmetrical split spread consisting of 12 geophones arranged 6 on each side of the source (see handout).
Bring questions to class next Monday. Chart is due next Wednesday.
Complete your reading of Chapter 4. Dipping layer reflection events are covered on pages , with additional discussion on pages The idea of common depth point sorting is discussed on pages We’ve talked tangentially about resolution ( ) and velocity analysis ( ). We will be talking about stacking of CDP gathers ( ) and migration ( ). Discussions of migration will come later but it is helpful to be aware of the issues early on.
Look over problems 4.1, 4.4 and 4.8.
Tom Wilson, Department of Geology and Geography