xiv CONTENTS 



CHAPTER V 



Page 



Electrical Methods 437 



Electrical properties of rocks ; effects of moisture ; geologic age ; resistivities 

 of earth materials. Classification of methods. Spontaneous polarization 

 method ; operating principle ; field equipment ; field measurements ; interpreta- 

 tion ; examples of field work. Equipotential point and line methods ; theory ; 

 interpretation ; results of field work. Resistivity methods ; operating prin- 

 ciples ; fundamental derivations of current fiow ; layer problems ; electrode 

 configurations ; depth determination ; near-surface inhomogeneities. Lateral 

 and vertical exploration. Analysis of resistivity data. Field procedure and 

 equipment. Examples of field work. 



CHAPTER VI 

 Electrical Methods : Electromagnetic 580 



Physical principles. Magnetic field associated with current flow. Measure- 

 ment of magnetic fields. Conductive equipment for energizing the ground. 

 Magnetic measuring equipment. Inductive measurements. Search coils ; direc- 

 tional properties. Inductive equipment. Electromagnetic methods ; principles 

 of operation. Horizontal loop methods. Vertical loop methods. Examples of 

 field work. Patents. 



CHAPTER VII 

 Seismic Methods 639 



Seismic prospecting and seismology ; recording earthquakes. Seismic pros- 

 pecting ; wave propagation ; velocities of elastic waves and elastic constants ; 

 velocities of materials. Propagation of seismic waves. Refraction and reflec- 

 tion phenomena. Reflection method ; travel-time curves ; AT. Dip calcula- 

 tions ; dip shooting. Velocity-depth functions ; lineal increase with depth. 

 Computation charts. Two-component dip-shooting. Type of spreads. The 

 recorded reflection. Examples of field work. Reflection correlation shooting. 

 Low-velocity layer ; evaluating effects ; corrections. Application of least 

 squares. Velocity shooting ; curvature effects. Continuous seismic profiling ; 

 fault mapping; grading of reflections. Cross sections and maps. Graphical 

 analogue computer. Refraction method ; ray paths and depth relationships ; 

 correlation of refractions. Multiple refractions ; examples of field work. 

 Intersecting spreads ; fan shooting. Instruments. Seismometers ; theory ; 

 types. Recording equipment ; filters ; gain control ; amplifiers ; galvanometers ; 

 oscillographs ; timing ; photographic papers and development. Instrumental 

 analysis ; variable area recording and filtering ; phase effects ; phase analyzer ; 

 frequency analysis and wave propagation ; frequency patterns. Equipment for 

 seismic prospecting ; truck equipment ; portable equipment ; truck body types ; 

 auxiliary service and surveying trucks. 



Field operations, refraction and reflection. The exploration crew; duties of 

 crew members. Transportation: trucks, marsh buggies, helicopter. Amount 

 and depth of explosive. Seismometer spreads ; relation between surface waves 

 and spread. Methods for improving reflections ; multiple detection. Over- 

 lapping spreads. Multiple shot-points. Generation of seismic waves : mechan- 

 ical, explosives. Types of explosives ; blasting caps ; electric firing. Loading 

 procedure; safe practices. Drilling equipment; types of drills; drill rods and 

 bits ; sizes ; portable drills ; water trucks ; drilling crew performance ; auxiliary 

 equipment and tools. Air shooting; explosive pattern. Multiple reflections; 

 examples from field work. Offshore seismic operations: instrumentation; 



