Fractal characteristics of active normal faults: an example of the eastern Gulf of Corinth, Greece

Abstract

We present a model proposing the evolution of segmented normal faults in a currently extended area, allowing an explanation of strong earthquakes hosted by short faults. Active normal faults accommodating the current extension in the Gulf of Corinth result from the linkage of smaller-component faults. Well exposed fault zones in the Sofiko range are arranged as pairs of graben-bounding faults and thus our structural analysis has implications for the evolution of active normal faults as well as graben evolution. A basal strip of fresh bedrock at the base of fault scarps suggests continuous seismic or aseismic creep. Thus the structural analysis of component faults, that show a power-law length distribution, describes an evolved fault zone. Of particular interest is that faulting in this region is self similar between limits. Distribution is characterized by a fractal dimension of D≈1, and the limits in our study are between 10 m (mapping resolution) and double the maximum displacement of each fault zone. Component segments of any compartmentalized fault show a length-to-maximum displacement ratio of two. Basin architecture and structural analysis suggest that the nucleation points of faults are detectable over the entire evolution of the fault zone. All analyzed faults evolved by an independent nucleation model. Morphotectonic and kinematic data, as well as fractal dimension of trace length population plots, all suggest that fault zones defining north- and south-dipping conjugates are active at least over the late stages of basin evolution. Although this study was focused on a relatively small area, this pattern of fault growth appears to be applicable to the entire fault population in the Gulf of Corinth and is thus an important model for normal faults.