GEOL 305 Final, Fall 1997

’ ny . i AN TUN Rsey j LIBRARY AMERICAN UNIVERSITY OF BEIRUT Ineo! Geology Department Geology 305 Final Exam February 3, 1998 Student Name: Part I. Choose the best answer (50 pts.) 1. The self-potential (SP) method has been used since 1920 in: a. metal exploration b. groundwater investigations c. geological mapping d. geothermal investigations 2. The self-potentials range from less than... to over... volt, and the . . . of the anomaly is an important diagnostic factor. a. 100mV...10... pattern b. amillivolt (mV)... one... pattern c.100mV... 10... sign d. a millivolt (mV)... one... sign 3. Electromechanical potentials belong to . . . potentials. a. mineral b. Nernst c. electrokinetic d. diffusion 4. There are two techniques in the measurements of self-potentials. In the potential gradient method, the two electrodes are moved at a. . . separation, whereas in the potential amplitude method, one electrode 1s kept tixed at a base station on... ground and the second one is moved along the traverse. a. fixed... unmineralized b. varying... unmineralized b. fixed... mineralized d. varying... mineralized 5. The main current application of induced-polarization (IP) method is in. . . exploration. a. ore-bodies b. disseminated metallic-ores c. geothermal d. groundwater 6. The exact causes of induced polarization phenomena are .. . the two main mechanisms are . . . polarization and . . . polarization. a. still unclear, but . . . grain (electrolytic) . .. membrane (electrode) b. still unclear, but... grain (electrode) . .. membrane (electrolytic) c. well known, and... grain (electrolytic)... membrane (electrode) c. well known, and... grain (electrode) . .. membrane (electrolytic) Dr. K. Khair Geology 305 tkefid—Eown) 7. The most common configuration used in the measurement of IP method is the . . . array. a. Wenner b. Schlumberger c. pole-dipole d. dipole-dipole 8. Inthe... IP, the measurements are taken over a wide range of frequencies (0.3 - 4 kHz). a. time-domain b. frequency-domain b. phase d. spectral 9. Due to... conductivity, the GPR method has very . . . use in the investigation of landfills. a. low... limited b. high... limited b. low... wide d. high... wide 10. The basic difference between Sundberg’s and Turam techniques (large-loop systems) is in the: a. size of the loop b. magnitude of the source c. number of receiving coils d. orientation of the coils and the loop 11. In the time-domain electromagnetic systems, the primary field is provided in. . . and the secondary field is measured while the primary field is (switched)... . a. sinusoidal form... on b. pulses... on b. sinusoidal form . . . off d. pulses... off 12. In most of the electromagnetic methods, except for GPR, the frequencies of the primary field are usually less than a few . . . hertz, therefore the attenuation associated with the propagation of the primary wave .. . be disregarded. a. thousand... can b. tens of... can b. thousand... cannot d. tens of... cannot 13. Several EM methods, such as . . ., exploit the tilt or dip angle of the ellipse of polarization. a. VLF and TEM b. VLF and AFMAG b. FEM and TEM d. FEM and AFMAG 14. The depth of penetration of the EM radiation depends on the: a. length of the array b. frequency of the signal c. conductivity of the media d. all of the above e. none of the above Dr. K. Khair Geology 305 (vtrdsderr) 2 15. The most commonly used airborne EM systems are deployed from . . . as they can be operated at. . . flying height. a. helicopter... low b. fixed-wing aircraft... low b. helicopter... high d. fixed-wing aircraft... high 16. The critical factor in seaborne EM surveying is that the sea water is extremely: a. resistive b. conductive c. dense d. saline 17. In the tilt angle methods, the conductive ore body is located under the point where the tilt: a. is maximal b. is minimal c. passes from positive to negative d. all of the above e. none of the above 18. In Turam method, the degree of . . . of the reduced ratio (RR) anomalies increases with . . . dip of the ore body. a. asymmetry... decreasing b. fluctuation... decreasing b. asymmetry ... increasing d. fluctuation . . . increasing 19. The static cultural noise, as one of the three sources of error in TEM, is caused by: a. topographic effects b. AC power lines and VLF transmitters c, distant lightning d. buried pipes, cables or other metals 20. .. . can be extremely useful in hydrogeological investigations using TEM. a. Reduced ratio plots b. Vector plots b. Apparent resistivity soundings d. Response contours 21. The main disadvantage of the mageto-telluric method is the: a. large depth of investigation b. long stacking time per site c. wide range of frequencies d. expensive transmission 22. When applied for engineering applications, the antenna frequencies of GPR systems should be more than. . . M. Hz. a. 10 b. 50 c. 100 d. 500 23... . is the most effective geophysical tool used in police investigations. a. VLF b. GPR c. TEM d, FEM Dr. K. Khair Geology 305 (hfebetieerr 24, The downgoing signal of radiowave propagating in a cone of radiation influences . . . resolution. a. vertical b. horizontal c. vertical and horizontal d. none of them 25. In... deployement of GPR, the transmitter and receiver are on opposite sides of the medium under investigation. a. transillumination b. wide-angle reflection and refraction c. common mid-point sounding d. radar reflection profiling Part II. Answer only five of the following seven questions (50 pts.) 1. Discuss the basis for the usage of SP method in two of the following applications: geothermal, location of massive sulphide ore bodies, hydrogeology, landfills, leak detection within embankments; draw diagrams if necessary. 2. Discuss the forms of display of IP data (time-domain and frequency-domain), draw diagrams. Describe the large-loop systems and draw their layouts, draw diagrams. Discuss the principles of operation of the very-low-frequency (VLF) method. 5. Using the shown figure (Fig. 1), explain the relationship between induced voltages and associated phase lags of different magnetic fields. ewe (A) (B) () (D) Figure 1 Dr. K. Khair Geology 305 @udka=Pere:) 6. The phasor diagram (Fig. 2) is the plot of an EM sounding method. Name and explain this method, and how the diagram is interpreted. In-phase (%) T T T -20 +10 28 160 \ Frequency (Hz) Quadrature (%)} Figure 2 Dr. K. Khair Geology 305-Arigeisiiionmn) 7. Name (inside the loops) the basic elements of the given fgure (Fig. 3) and define the monostatic and bistatic modes of GPR. (A) COMPONENTS OF C » ( - —) RADAR SYSTEM “> Source and modulation Data storage Signal sampling and digilisation es Re1 bce EH 1 eat sp eietts San a Naihe GOOD LUCK Dr. K. Khair Geology 305 (hiebaaPrrs)