A fault, once formed, long remains a plane of weakness, and stresses developing in the adjacent region are more likely to be relieved by adjustments along it than by the formation of new faults. This is especially true of faults that persist for long distances. The identification of active faults is of importance, since they are the loci of earthquakes, each new displacement of a growing fault resulting in an earthquake.
The criteria that have been used in recognizing active faults are: (1) the recurrence of earthquakes along faults, and (2) physiographic and geologic evidence of recent displacement; but each of these may be misleading unless the general stability of the entire circumjacent region be taken into consideration.
The Charleston earthquake of 1886 was one of the greatest recorded in North America, and aftershocks have continued in its epicentral area down to the . . .