(Km) Max. Finite throw (m) Error in (m) Locality Number (Fig. 5.1) XUTM Coordinate Y UTM Coordinate Post glacial Throw (m) Error in (m) Throw-rate (mm/yr) Data source Notes Pollino 32 800 300 0605483 4412366 6 0.33 0.35-0.4 S.P. T.
Data from Vittori et al., 1995b; Michetti et al., 1997.
30 0605223 4412845 5.4 1.1 0.3 S.P. Bedrock scarp.
31 0611287 4409150 3.5 0.7 0.19 S.P. Bedrock scarp.
32 0588419 4416598 4-4.5 1.8 0.22-0.25 E.E Bedrock scarp, lower slope
disturbed by cultivation.
0.2-0.5 S.P. Data from Cinti et al., 1997; 2002 (Castrovillari fault).
Mercure 32 1100 200
33 0581379 4430162 3 0.6 0.17 S.P. Alluvial carp in a chestnut wood
forest
34 0582178 4429629 6.7 1.3 0.37 S.P. Bedrock scarp on the continuation
of the previous scarp, a few hundred meters towards the SE.
Monte Alpi 33 1500 400
35 0582017 4440880 9-10 3.6 0.55 E.E. 5-6 m polished fault surface plus 3-
4 m of degraded scarp, along the steep limestone escarpment.
Maratea 37 1600 400 36 0562700 4429519 7.8 1.6 0.43 S.P. Bedrock scarp, a portion of the
upper slope is exposed.
Val’ D'Agri 41 2100 500
0564879 0564853
4475800 4476092
15 0.83 E.E. Data from Benedetti et al. 1998.
37 0571296 4468174 9 1.8 0.5 S.P. Lower heavily degraded bedrock
scarp.
38 0570741 4469864 6 1.2 0.33 S.P. Upper bedrock scarp.
15 3 0.83 S.P. Cumulative postglacial throw
(Upper scarp loc.37 4- lower scarp loc.38).
39 0538726 4491971 8 1.6 0.44 S.P. Considerable post glacial throw
variation along strike over short
Vallo di Diano
45 1550 400
40 0538539 4492238 7.3 1.5 0.41 S.P. distances. Postglacial throw
diminishes towards the NW tip of the fault, from 8 m to 7.3 m and 3.3 m, 4 km, 3.5 km
41 0537182 4492810 3.3 0.7 0.18 S.P. and 2 km away from the tip,
respectively.
42 0545958 4479775 9.8 2 0.54 S.P. Bedrock scarp, lower slope is
disturbed by cultivation.
Albumi 25 1150 150 43 0532258 4485676 6-7 3.6 0.39 E.E Bedrock scarp is hidden by the
vegetation.
Iprinia 31 1050 200
44 0515232 4520580 9.8 2 0.54 S.P. Bedrock scarp in a chestnut wood
forest.
0.25-0.35 T. Data from Pantosti et al., 1993. Irpnia
Antithetic
15 45 0542557 4514780 4 0.8 0.22 S.P. Bedrock scarp near Bella.
San Gregorio 20 1150 250
46 0532772 4502364 5.3 1.1 0.29 S.P. Bedrock scarp on the SW dipping
fault.
0.3 T. Data from D'Addezio et al., 1991 on the NE dipping fault.
47 0538239 4500441 1.5 0.08 E.E. Postglacial throw diminishes
towards Balvano village.
Volturara 30 950 300 <0.3 E.E. No bedrock scarp observed,
possibly covered by lake sediments. Note: Locality numbers represent only throw-rate observations. Maximum finite throw values are presented in meters and are extracted from cross sections. The source of throw-rate data is distinguished, showing whether throw-rates are from scarp profiles (S.P.), or from eye-estimations (E.E.) or from published trench investigations (T).
C hapter 5
5.3.1.1 Methodology
The traces of all major active normal faults in the southern Apennines were identified, checked on published geological maps and in the field and in places remapped using 1:100000 topographic maps. The map of the study area is presented in Figure 5.1b. The bedrock map was modified and simplified from CNR (1990) and transformed into the UTM coordinate system through an Arcview software projection utility extension. The goal was to determine the positions and lengths of all the major active faults in the region. This task can be problematic, especially as far as the fault lengths are concerned, because vegetation cover restricts the view for the majority of the faults and can hide scarps as high as about 10 m. Moreover, the faults appear to be segmented at a length scale of c. 5-15 km with small-scale en echelon fault overlaps (transfer zones or relay ramps) separating different fault segments. Additionally, some of the faults have very subtle geomorphic expressions where they enter rock types such as flysch or foredeep deposits, in which faulting is poorly preserved. In many cases, this is true for the fault tips where the total offset is small; generating the main source of errors for the determination of fault lengths. Thus, to help establish a more accurate evaluation of fault lengths, finite throws, throw-rates and occasionally, slip direction data were used (see Section 2.1). Finite throws and throw-rates were extracted from a number of cross sections and scarp profiles constructed across each major active fault respectively. More details of the methodology used and the implied errors are presented, in the following Sections 5.3.1.1.1 and 5.3.1.1.2.
5.3.1.1.1 Scarp profiles, estimated throws and errors
Deformation rate information in the region of the southern Apennines has been derived from displaced post-glacial sediments and landforms associated with the last major glacial retreat that occurred in the region c. 18,000 years ago (Section 5.2). A similar methodology to that described in detail in Lazio-Abruzzo (Section 4.3.1.1) was followed. Quantitative data were extracted from topographic profiles measured perpendicular to the trace of the scarp where the vertical offset of the glacial surfaces corresponds to the total throw of each fault during the last
18 kyrs.
In order to extract deformation rates, several scarp profiles were constructed on 8 different active faults. Also, in a few localities (4 out of 18 localities) the throws associated with scarps were estimated by eye. Throw values were estimated in the field and then were corrected in the laboratory after examining photos with clear objects for scale included in the photographs. All
C hapter 5
the profiles were constructed through chain surveying techniques using a ruler (1 meter) and a clinometer. The profiles exhibit common features characteristic of fault scarps (e.g. Yeats et al., 1997), such as the upper slope, the degraded scarp, the free face, the colluvial wedge and the lower slope (e.g. Fig. 5.4i).
After defining the main profile characteristics in the field, the profiles were reconstructed and interpreted into a graphics package and the throw post 18 kyrs was calculated. The post 18 kyrs throw is defined as the height measured between the intersection of the fault plane with the upper and the lower slope respectively.
Overall, the errors involved in the construction of scarp profiles in the region of the southern Apennines are similar to the errors described in Lazio-Abruzzo (Section 4.3.1.1.2). In most cases the slopes are smooth and almost planar, and the profiles are relatively long, so the error introduced by defining a strain line that represents the dip of the slope is insignificant. Also in the majority of the profiles the free face is exposed constraining the fault dip. However, even if the profile site selection has been chosen very carefully, it is inevitable that the scarp morphology has been altered to some extent by weathering and deposition. As a result, the postglacial throw could be underestimated. Where eroded gullies exist on the lower slopes exposing their stratigraphy, it is clear that the thickness of the organic-rich post 18 ka soils are generally only a few tens of centimetres, overlying the organic-poor upper Pleistocene pre 18 ka colluvium. Thus, burial of the scarps is typically limited to only a few tens of centimetres, an error that is small (< c. 5%) compared with the throws across scarps, which are in the order of a number of metres high. Finally, scarp throw variation along strike is evident, even over short distances, including locations that are apparently undisturbed by incision or deposition processes. This throw variation is most likely to be the natural variation associated with coseismic surface slip and constitutes the main source of uncertainty. The overall estimated error is about ± 20 per cent of the postglacial throw value. Similarly, the proportional estimated error for an 18 m high scarp that offsets an 18 ka slope, resulting in a throw-rate of 1 mm/yr, is calculated up to about ± 3.6 m or 0.2 mm/yr in terms of throw-rates.
Finally, for a few locations the throws across scarps were estimated by eye in the field and corrected later in the laboratory by examining photos with scales on them. For these locations the errors are probably greater. For instance, vegetation can easily hide a portion of the main scarp or other smaller secondary scarps, but the main difficulty arises in the determination of the degraded scarp, which is usually hard to see and very difficult to evaluate without a profile. These errors apply to all visually estimated postglacial throws, but the error quantification varies according to the scarp characteristics. In the southern Apennines, all the scarps that have
C hapter 5
been calculated by eye exhibit low throw-rates (<0.6 mm/yr), so an error of ± 3.6 m (± 0.2 mm/yr) is estimated for scarps of 5.4 m to 10.8 m high (0.3-0.6 mm/yr) and an error of ± 1.8 m (± 0.1 mm/yr) is introduced for scarps less than 5.4 m high (<0.3 mm/yr).
5.3.1.1.2 Cross-sections and errors
A number of cross-sections have been constructed across each major active fault, using published 1:100000 topographic and geological maps (Servizio Geologico D’ Italia Potenza, 1969; Verbicaro, 1970; Lauria, 1970; S. Angelo de’ Lombardi, 1970; Eboli, 1970; Castrovillari, 1971; Salerno, 1969) (Fig. 5.3). The cross-section transects are several kilometres in length, perpendicular to the fault trace, and wherever they cross closely spaced faults, the cumulative throw values were calculated. All finite throw data were measured from the cross sections presented in this study (Fig. 5.3) with the exception of the Monte Alpi fault where no detailed geological maps are available. In that case, a finite throw value was extracted from the Corrado et al. 's (2002) cross section based on subsurface data (seismic reflection profiles and deep well logs).
Errors on finite throws are variable, but they were quantified for every cross section, based on the stratigraphie column displayed on each geological map. Throw-distance profiles were constructed for each fault and fault tips were located in places where finite throws were estimated that decrease to zero.
5.3.1.2 Field observations, interpretations, finite throws and deformation rates of individual faults
In this Section, the fault pattern is presented in detail with particular emphasis placed on throw- rates and finite fault throws. A fault-by-fault discussion is offered for each of the 10 individual active faults identified in the investigated area. Additionally, throw-rates extracted from this study are combined and compared with published rates (from trenching studies and visually estimated throws) in order to offer a complete picture of the deformation rate pattern. Postglacial and finite fault throws are presented in meters and throw-rate is deduced by dividing the postglacial throw over 18 kyrs. The positions of studied localities were constrained using