FRACTAL ANALYSIS OF A QUATERNARY FAULT ARRAY IN THE CENTRAL APENNINES, ITALY

The Monte Vettore fault array, in the central Apennines fold and thrus t belt, is part of a major Quaternary fault system displaying the main features of a regional negative flower structure associated with a ro ughly N-S-trending left-lateral strike-slip fault zone. Fractal analys is of the fault trace pattern of the area has shown that the box-count ing curve derived for the Monte Vettore array is defined by two straig ht line segments, each showing a characteristic slope value. The first segment, which refers to a spatial distribution extending over about one order of magnitude, is characterized by a fractal dimension of abo ut 1.6, whereas the second one fits a Euclidean (i.e. a non-fractal) d istribution. Tl-le box-counting analysis emphasizes that faults with v ariable sizes exhibit different scaling relations, hence suggesting th at fault linkage played a major role in the development and evolution of the Monte Vettore fault array. The split point between the two segm ents falls at a value of log 1/s, corresponding to a box size of 635 m , hence suggesting that self-similarity among faults within the array breaks down below this value. Fractal analysis of the Monte Vettore ar ray also provides statistically-based segmentation criteria for analys ing a young immature fault structure capable of generating medium-size earthquakes in a continental geotectonic setting. (C) 1997 Elsevier S cience Ltd.