جامعة الملك سعود                                                                 مقرر 312جاف

قسم الجيولوجيا                              الاختبار النهائي 1424 هـ

First Semester, 1423

First Mid-term Exam.                                                                    Abdullah M. AI-Amri

Answer the following questions :

I. Define the following terms :

Damping Factor

Man-Made Seismic Sources

Lg, ScP, PKIKP , S *

Dynamic Range

Inverse Dispersion

Quality Factor

2. Miscellaneous :

 

 

a. Compare between Short and Long Period Seismometers.

b. Sketch the variations of group and phase velocities in oceanic and continental paths.

c. What are the factors which influence the amplitude of seismic phases. Classify how the vertical and horizontal  components can record different seismic waves.

d. Derive the relationship between the group and phase velocities. 
3. Multiple choice. Select only one answer :

a. Seismic waves transmitting inner core are

I. SKS       2. PcP         3. PKIKP          4. PKiKP

b. Seismic wave energy travels with

I. group              2. phase               3. group & phase velocities                   4. none of them

 

c. Clipping (saturation) is appeared mainly at  M>6 on

1. analog seismogram    2. Digital seismogram     3. Seismometer       4. None of them    

d. Always concentrate near discontinuity

I. surface waves            2. Primary waves           3. Shear waves

8  Always exhibit dispersion

1. Rayleigh                             2. P-wave                             3. S-wave             4. Love

f. When group < phase velocity

1. normal dispersion                          2. inverse dispersion              3. no dispersion

g. The seismic instrument is known as

I. seismometer        2. seismoscope              3. seismograph           4. seismogram

 

h. Earthquakes at epicentral distance between 70 and 90 degrees are

 I. regional 2. teleseismic 3. local 4. none of them

i. Moho discontinuitiy was discovered in

1. 1909          2. 1900              3. 1950                      4. 1935

j. The amplitude decrease is called

8 1. Absorption                        2. Attenuation              3. Quality factor

k. The attenuation is greatest in the

1. Crust                     2. Mantle                        3. Outer core              4. Inner core

L. STS-2 is a seismometer designed for

1. broadband                       2. short-period             3. Long-period

 

M. A 24 bit resolution is characterized for seismometers of

 1. short-period                     2. Long-period            3. Broadband

 

N. If S-P is less than 20 sec, the first arrivals are

I. Pg                    2. Pn                 3. Lg                     4. PmP

 

P. It has the largest amplitude and best seen on horizontal components

1. Sg                       2. Pg                  3. Lg                          4. Rg

T. If the damping factor = I , it corresponds to

1. Underdamped             2. Critical damped               3. Undamped             4. Overdamped