1
LOYOLA COLLEGE (AUTONOMOUS), CHENNAI 600 034
M.Sc.DEGREE EXAMINATION PHYSICS
SECONDSEMESTER APRIL 2018
17/16PPH2ES02- GEOPHYSICS
Date: 25-04-2018 Dept. No. Max. 100 Marks
Time: 01:00-04:00
PART A
Answer ALL Questions (10x2=20)
1. How human activities induce an earthquake?
2. Neatly draw horizontal seismograph and mention its parts.
3. If the P-wave velocity is 7 km/s and Poisson's ratio is 0.25.Calculate velocity of S-wave.
4. Define magnetic Reynold's number.
5. Differentiate tensional and shallow earthquakes.
6. What is magma? How it occurs?
7. Find the radiation activity of 1mg of Sr90.The half-life period of Sr90 is 26 years.
8. Is Earthquake's magnitude same as its intensity. Explain.
9. List out the factors that influence acceleration due to gravity.
10. What do you mean by electric mapping?
PART B
Answer any FOUR Questions (4x7.5=30)
11. Briefly discuss seismic discontinuity.
12. Explain Richter scale of magnitude analysis.
13. Determine the values of gravity at the following series of points belonging to a gravimetric survey with a Worden gravimeter, specifying the draft correction for each of them.
Station
Time
Reading
A(base)
08:50
562.5
B
09:21
400.7
C
11:34
437.9
D
13:20
360.1
A
14:33
568.8
The gravity at the base is 980.13982 Gal, and the gravimeter constant is 0.31081 mGal/ru (ru:Reading unit)
14. Draw neatly and explain the working principle of Worden gravimeter.
15. What are the factors affecting resistivity? Explain data collection.
16. Describe the working of Flux gate magnetometer.
2
PART C
Answer any FOUR Questions (4x12.5=50)
17. What are techtonic plates? How are zone boundaries formed?
18. Derive seismograph equation with damping correction.
19. Distinguish between
Body waves and Surface waves
Rayleigh waves and love waves
Horizontal seismograph and vertical seismograph
20. What is Isochron plot? Describe the geochronology of Rb-Sr method?
21. Discuss in detail earthquake effects.
22. Write a short note on
Internal structure of Earth.
Earthquake mechanism.