Fault Trace Corrugation and Segmentation as a Measure of Fault Structural Maturity

As faults grow over time and become more mature, some of their geometrical and mechanical properties evolve, and these changes modify earthquake behavior. It is thus of prime importance to know the degree of structural maturity of a fault that is likely to produce large earthquakes. Although this concept is extensively used, there is no common definition or metric to measure the structural maturity of a fault. We analyzed the heterogeneity of the surface traces of 13 large seismogenic faults whose maturity is known qualitatively. We measured the corrugations and step-over segmentation of the traces from similar to 100 m to the fault length scale. Corrugations and some properties of the segmentation are found to vary with fault structural maturity. We provide scaling relationships that quantify the structural maturity of a fault based on its surface trace. These results should help in parameterizing source faults in earthquake models. Plain Language Summary Long-term faults produce earthquakes. Measuring fault properties could thus help us understand earthquake behavior. However, measuring properties of large-scale faults in particular is difficult. Here, we tackle one of the major long-term properties of faults, their structural maturity. This property relates to the overall slip longevity of the fault (generally several million years), and it has been shown to impact earthquake behavior; mature and immature faults do not behave similarly. For 13 large seismogenic continental faults whose structural maturity was estimated qualitatively in earlier works, we examined the heterogeneity of the traces these faults form at the ground surface. Using simple tools, we measured the undulations and the discrete stepping segmentation of the fault traces over a broad range of scales from similar to 100 m to the full fault length (up to similar to 1,600 km in this study). We found that the intensity of undulations and the density, relative width, and size diversity of the steps separating discrete fault segments all vary with the structural maturity of the faults. These variations are described with simple mathematical functions that characterize fault structural maturity and can be used to better represent source faults in earthquake models. Key Points We measure the corrugation and step-over segmentation of 13 large seismogenic fault traces, at scales greater than similar to 100 m The corrugation level and the step-over density, relative width, and size diversity vary with the structural maturity of the faults We provide scaling relations measuring fault structural maturity, which should help to describe source faults better in earthquake models

Automated summary

The study examines the impact of fault structural maturity on earthquake behavior, analyzing the corrugation and segmentation properties of fault surface traces to propose scaling relationships for quantifying fault structural maturity. These findings aim to enhance the representation of source faults in earthquake models.