Fault Interactions Enhance High‐Frequency Earthquake Radiation.

Fault complexity has been linked to high‐frequency earthquake radiation, although the underlying physical mechanisms are not well understood. Fault complexity is commonly modeled with rough single faults; however, real‐world faults are additionally complex, existing within networks of other faults. In this study, we introduce two new ways of defining fault complexity using mapped fault traces, characterizing fault networks in terms of their degree of alignment and density. We find that both misalignment and density correlate with enhanced high‐frequency seismic radiation across Southern California, with misalignment showing a stronger correlation. This robust correlation suggests that high‐frequency radiation may arise in part from fault‐fault interactions within networks of misaligned faults. Fault‐fault interactions may therefore have important consequences for earthquake rupture dynamics, energetics and earthquake hazards and should not be overlooked. Plain Language Summary: The faults on which earthquakes occur sometimes form complex interconnected patterns. The level of this complexity may promote higher frequency ground motions coming from earthquakes occurring on such faults. We describe ways of quantifying the complexity of groups of faults based on how they are aligned and how densely they are spaced. We find that high‐frequency ground motions in Southern California tend to correlate with misaligned faults, suggesting that structural interactions between different parts of the fault system may play a role in generating the ground motions felt during earthquakes. Future work involving rupture simulations, ground motion modeling, and hazards assessments in complex fault geometries should consider the effects of these structural interactions. Key Points: We introduce two new metrics quantifying the complexity of interacting faultsIn Southern California, enhanced high‐frequency seismic radiation is associated with earthquakes on misaligned faultsHigh‐frequency seismic radiation may thus be produced in part by fault‐fault interactions [ABSTRACT FROM AUTHOR]