Geophysics Iii

1. Understand the electrical properties of rocks and their influence on geophysical measurements.
2. Apply direct current resistivity methods for subsurface investigation.
3. Analyze varying current methods in electromagnetic surveys.
4. Interpret resistivity profiling and depth sounding data.
5. Explain the principles of VLF radiation and its applications.
6. Evaluate natural and controlled-source audio-magnetotelluric techniques.

13 weeks, about 43 hours in total. Yours will differ.

1. Week 1MODULE 1

   • Unit 1: Electrical Properties Associated with Rocks · 3 hours

     Understand the basic concept of electric current methods.. Identify and understand the electrical prospecting phenomena and properties associated with Rocks.. Understand that Resistivity governs the amount of current that passes through the rock when a specified potential difference is applied..

2. Week 2MODULE 1

   • Unit 2: Direct-Current Resistivity Methods · 3 hours

     Understand clearly the Direct- Current Resistivity Methods especially its definition and application. Understand the usefulness of metal electrodes, Non polarising electrodes in application of DC Resistivity methods.. Know that DC surveys require current generators, voltmeters and electrical contact with the ground..

3. Week 3MODULE 1

   • Unit 3: Varying Current Methods · 3 hours

     Know that current are caused to flow in the ground by alternating electrical or magnetic fields obtain their energy from the fields and so reduce their penetration. Understand that varying magnetic field associated with an electromagnetic wave will induce a voltage (emf) at right-angles to the direction of variation. Know that most continuous wave system, the energizing current has the form of a sine wave, but may not, as a true sine wave should, be zero at zero time (sinusoidal).

4. Week 4MODULE 2

   • Unit 1: Resistivity Method · 3 hours

     Understand the concept of DC survey fundamentals which includes Apparent resistivity, electrode arrays and Wenner array.. Understand commons electrodes array such as wenner array, two electrode, Schlumberger and gradient methods of arrangement. etc.. Familiar with the common electrode arrays descriptions..

5. Week 5MODULE 2

   • Unit 2: Resistivity Profiling · 3 hours

     Know and understand the concept of Resistivity Profiling. Know that resistivity traversing is used to detect lateral changes in subsurface... Know that depth information can only be obtained from a profile.

6. Week 6MODULE 2

   • Unit 3: Resistivity Depth Sounding · 3 hours

     Investigate layering using arrays in which the distances between some or all of the electrodes are increased systematically.. Understand that the Wenner array is very popular but for speed and convenience, the Schlumberger array, in which only two electrodes are moved, is often preferred.. Know that site selection is extremely important in all sounding work, is particularly critical with the Schlumberger array, which is very sensitive..

7. Week 7MODULE 3

   • Unit 1: Electro-Magnetic Methods · 3 hours

     Understand the concept of conductivity (r), the reciprocal of resistivity. Know that EM methods tend to focus on conductivity rather than resistivity itself.. Understand the system descriptions of continuous wave EM.

8. Week 8MODULE 3

   • Unit 2: Other CWEM (Continuous Waves Electromagnetic) Techniques · 3 hours

     Understand the concept of continuous wave electromagnetic Techniques.. Practicalise and demonstrate fixed source method and be able to apply it to measure dip angles or ratios of vertical to horizontal fields.. Use higher frequency alternating electromagnetic fields through long wire sources instead of vertical and coplanar coils to study the real and imaginary components of the electrical properties of the subsurface geoearth materials..

9. Week 9MODULE 3

   • Unit 3: Transient Electromagnetic · 3 hours

     Know Transient that Electromagnetic are used for depth sounding. Familiarise with both CWEM, TEM and time domain IP systems. Understand that transient electromagnetic was developed to overcome some of the disadvantages in CWEM..

10. Week 10MODULE 4

    • Unit 1: Very low Frequency (VLF) Radiation · 3 hours

      Know that natural electromagnetic radiation covers a much broader range of frequencies.. Understand that electromagnetic wave consist of a coupled alternating electrical and magnetic field directly at right angles to each other. Familiarise with the VLF TRANSMISSIONS.

11. Week 11MODULE 4

    • Unit 2: VLF Instruments · 3 hours

      To demonstrate EM-16 add-on module to measure horizontal electric field. Know that EM-16 is still widely used and serves to illustrate practical principle which are concealed by processing software in some instruments. Be familiar with other VLF instruments..

12. Week 12MODULE 4

    • Unit 3: Presentation of VLF Results · 3 hours

      Explain filtering and the purpose why noise has to be filtered. Understand that VLF dip angle data are mostly effectively presented as stacked profiles. Understand the VLF system operate at a relatively high frequencies at which most conductors appear good..

    • Unit 4: Natural and Controlled-Source Audio-magnetotellurics · 3 hours

      Explain the source of controlled sources, Auto- Magneto Telluric (CSAMT) and its principles. Know the parameters mostly commonly measured in CSAMT. Compare results of AMT and CSAMT sounding over a simple layer earth.

13. Week 13MODULE 5

    • Unit 1: Field Work · 4 hours

      Know the major fields of application of electrical and electromagnetic methods.. Show precisely where electrical and electromagnetic methods are suitable in mineral and environmental studies.. Show how the various geophysical methods complement one another..