Reflection seismology

Question 1

What is meant by two-way time?

Answer 1

The time to reach the reflector and back

Question 2

What is normal move out?

Answer 2

The later time of arrival of rays to receivers further away from the source. To deduce the velocities of the subsurface layers, a number of receivers along the line is needed, offset to one or both sides of the shot point.

Question 3

What is the common midpoint/common depth point gathering?

Answer 3

To stack rays that have all reflected from the same point of an interface by using pairs of shot points and receivers that are symmetrical about the reflecting point. The rays are fired successively, so the traces have to be extracted from recordings of successive shots.

Question 4

What is the fold?

Answer 4

The number of channels that are added together, or gathered, is termed the fold of the stacking

Question 5

What are the uses for reflection seismology?

Answer 5

• Hydrocarbon exploration
• General earth structure knowledge
• Local structures knowledge (Geotechnical and environmental work)

Question 6

What is seismic imaging?

Answer 6

Plotting many traces of reflected seismic waves yields an image in which structures can be observed.