Lecture 2 - Seismics B

Question 1

What is Snell’s Law?

Answer 1

The formula which describes the relationship between the angle of incidence and refraction when waves pass through a boundary between two mediums

Question 2

At the critical level r=90’, what happens to waves above the critical level?

Answer 2

They are refracted

Question 3

What can we interpret from refraction seismic data?

Answer 3

•Measure travel times of first breaks
• Plot times on a time-distance graph
•Measure V1, V2 and T1 (the intercept time
between direct and refracted arrival lines Xcross in
practical)
• Calculate angle of reflection and refraction (from
Snell’s Law – handout A-2)
• Calculate thickness of upper layer using this angle

Question 4

What affect can inclined rock layers have on seismic data?

Answer 4

Can delay time it takes for waves to reach geophones