1. Observation of the seeps has led to the discovery of many of the worlds great oil fields. 2. Once such a likely area is found, then more specific tests and investigations are made and the information gained from these is used to construct maps of the earths substructure. 3. By 1920 it was found that looking for domes, seeps and anticlines on the surface maps was not sufficient. 4. Thus geophysical methods were devised. 5. The first method developed was the torsion balance, followed closely by the seismograph. 6. With the seismograph, subsurface structures can be deduced by measuring the transit times of sound waves generated by an explosion. 7. Other tools developed for use by geophysicists are gravity meters and magnetometers. 8. The basic tool in any search for oil is a knowledge of the earth itself how it was formed, its composition and its present configuration. 9. Not every well drilled today is assured of a rich strike.
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