Source scaling properties from finite-fault-rupture models

Finite-source images of earthquake rupture show that fault slip is spatiall y variable at all resolvable scales. In this study we develop scaling laws that account for this variability by measuring effective fault dimensions d erived from the autocorrelation of the slip function for 31 published slip models of 18 earthquakes, 8 strike-slip events, and 10 dip-slip (reverse, n ormal, or oblique) events. We find that dip-slip events show self-similar s caling, but that scale invariance appears to break down for large strike-sl ip events for which slip increases with increasing fault length despite the saturation of rupture width. Combining our data with measurements from oth er studies, we find evidence for a nonlinear relationship between average d isplacement and fault length, in which displacement increases with fault le ngth at a decreasing rate for large strike-slip events. This observation is inconsistent with pure width or length scaling for simple constant stress- drop models, but suggests that the finite seismogenic width of the fault zo ne exerts a strong influence on the displacement for very large strike-slip earthquakes.