Not Just Rough Around the Edges: Fractal Properties of Exhumed Fault Surfaces in the Italian Apennines

Analysis of fault surfaces has shown the roughness to have fractal properties: there is a power-law relationship between the topography of a fault surface and the wavelength of this topography. Detailed analysis in recent years has shown fault surfaces to be smoother in the along-slip direction than perpendicular to slip. With this new understanding of the long-order behaviour of a fault surface over many spatial scales we are in an excellent position to further study earthquake friction, nucleation, slip behaviour and fault mechanics.
Here we present our investigation of fault roughness across the Italian Apennines. Using a combination of terrestrial laser scanning, laser profilometer and photogrammetry we have created 3D point clouds of fault surfaces, with resolution from sub-millimetre up to several meters. Results from over twenty scanned faults across the mountain belt are shown as well as an in-depth study of the Campo Felice fault. We also investigated the surface expression of faulting, which provides information on roughness at the kilometre scale.

Using this unique dataset across the Apennines we comment for the first time on the observable changes in fault roughness across a mountain range as a whole. We also link this to long-term slip histories and maturities of the faults. With our detailed scans along the entire length of Campo Felice we model the effects of localised fault geometry on earthquake propagation. Our measurements of the self-similar nature of the faults will also enable us in the future to better model coseismic slip for earthquakes in this region.