In this course we’ll study several of the fundamental methods of geophysics; that is, the application of physical measurements to solve geological and hydrological problems. These methods can be applied on many scales from the whole earth down to a building lot. The basic physics is the same at all scales although the details of technique may vary. Besides basic theory, the course includes weekly field labs in which we use the methods on local problems.

The first method we’ll study is "seismic refraction". In this method artificial seismic waves are generated and their arrivals back to the surface of the earth are observed and timed. The results are usually interpreted in terms of the subsurface distribution of wave velocities and hence of earth materials. Typical local goals would be estimation of water table depth and bedrock depth.

"Seismic reflection" is the second method we study. Here the ray paths of the seismic waves are primarily vertical and we look for echoes (reflections) from interfaces underground. This method is the mainstay of prospecting for oil and gas and also is the most important method in marine geophysics.

"Electrical resistivity" is our third method. We inject an electrical current into the ground and observe the voltages developed at the surface of the earth. The method is based on the fact that different earth materials vary in ability to transmit an electric current. Applications include distinguishing fresh groundwater from saline or clay from sand.

The "gravity" method is used to find anomalous buried masses and to estimate their sizes. In other words we measure the slight local variations in "g" that result from local density differences. In the fossil fuel business the method can be used to locate anticlinal and salt dome oil traps. In hydrology we can map buried valleys and other aquifers. We can even detect changes over time in groundwater levels.

"Magnetic field" measurements are the final method in this course. By measuring magnetic fields we can detect and trace igneous dikes, contacts, faults, foliation and other features of crystalline rock. We can locate drums of toxic waste, unexploded military ordnance and even map the walls and streets of buried cities.

The important electromagnetic methods such as ground-penetrating radar, magnetotellurics, VLF and so on are covered in ES934 or various spring semester short courses.