Airborne Magnetics Surveys

The magnetic properties of rocks can be mapped. As faults offset two different types of rocks, abrupt variations in the magnetic signatures may develop. Such variations are apparent along the offshore San Andreas fault system as shown below. More closely-spaced magnetic profiles are presently being acquired that will provide expanded coverage and more detailed information about the fault zones.

See full-size image (165 kb).

From Jachens, R. C., and Roberts, C. W., Aeromagnetic map of the San Francisco Bay area, California, USGS Geophysical Investigations Map, GP-1007, 1993