Seismological and structural evolution of strike-slip faults

The mapped traces of strike-slip faults are commonly characterized by discontinuities that appear as steps in map-view. Here I present observations to show that the number of steps per unit length along the trace of major strike-slip fault zones in California and Turkey is a smoothly decreasing function of cumulative geological offset. When coupled with a growing body of evidence that indicates that steps in fault traces work to impede or arrest the propagation of earthquake ruptures, the apparent smoothing of fault traces with displacement is interpreted to suggest that the spatial distribution of strength properties on a fault plane is a function of cumulative geological offset. A consequence of this structural evolution is that faults may undergo a seismological evolution a well, whereby the size and frequency distribution of earthquakes is also a function of cumulative offset.