Segmentation and interaction of normal faults within the Colfiorito fault system (central Italy)

Abstract

Fault segments belonging to a fault population can link and interact, eventually forming a single larger fault, and thus affecting the estimation of the maximum expected earthquake. We present throw distribution data along the Quaternary normal faults of the Colfiorito fault system (central Italy), which consists of four main fault segments and where a seismic sequence occurred in 1997-1998. Throw values along the two central overlapping, en-rchelon segments (8.5-9.5 km long) were measured on a good stratigraphic marker, by constructing a set of closely spaced geological cross-sections, perpendicular to the fault strike. As these faults are commonly retained active and border Quaternary basins, we compare morphological and geological throws in order to verify the faults neotectonic activity. Geological and morphological throw distributions show good correlation, testifying that recent faulting affected the topographic surface and suggesting that the observed offset completely accumulated during the Quaternary. The throw distribution along the fault segments is asymmetric and reaches maximum values (500-550m) within the zone of fault overlap, suggesting mechanical interaction between the studied faults. Maximum length-throw correlation suggests that the studied faults grew according to a linear scaling relationship.

Generic along‐strike segmentation of Afar normal faults, East Africa: Implications on fault growth and stress heterogeneity on seismogenic fault planes

“…These segments were identified either from the geometry of the surface fault traces, or from the cumulative displacement distributions. Most reported segments are “major segments” as defined in this study, but three studies [ McLeod et al ., ; Mirabella et al ., ; Lohr et al ., ] also report subordinate scales of segmentation. The faults have different lengths (in range 0.6–350 km), ages, slip rates and they developed in different tectonic and geological settings.…”

Seismic reflection data in the Umbria Marche Region: limits and capabilities to unravel the subsurface structure in a seismically active area

“…3) which cross the 1997-98 earthquake area. These sections do not image well the normal faults at depth due to the relatively small offsets of these faults (about 500-600 m, Mirabella et al, 2005), and to the fact that they superimpose similar rocks (carbonates and/or evaporites) with low impedance contrast (Stucchi et al, 2006;Mirabella et al, 2008).…”

Connecting seismically active normal faults with Quaternary geological structures in a complex extensional environment: The Colfiorito 1997 case history (northern Apennines, Italy)

“…Among these faults, the Colfiorito Fault System (CoFS; heavy black on Figure 3) consists of a set of about 15 SW dipping normal faults, grossly aligned in a ∼N140° direction, which represent the geologically and geomorphologically prominent structures of the area (Figure 4). If we compare the other normal faults present in the area, the CoFS possesses some distinctive characteristics: (1) a larger cumulative displacement (up to 600 m), measured on a well recognizable stratigraphic marker [ Mirabella et al , 2004]; (2) well exposed, frequently fresh fault surfaces (Figure 5); and (3) a clear topographic signature (see Figures 4, 5, and 6), i.e., the mean elevation of the footwall block is higher than the hanging wall block (1300–1500 m versus 800–1000 m, respectively).…”