6 m throw from a scarp profile (0.33 mm/yr) and a throw-rate of 0.35-0.4 mm/yr from trenching 0.2-0.5
1
Cinti et al., 1997; 2002
Rates reported for the Castrovillari fault. Long term rate of 0.2-0.5 mm/yr from scarp profiles and a short term rate o f 1 mm/yr from trenching Val’ D ’ Agri 1 Benedetti et al., 1998 15 m high postglacial throw estimated by eye,
averaged over 14 kyrs (0.83 mm/yr over 18 ka) Maratea Hippolyte et al., 1994 7-10 m high scarp estimated by eye
Vallo di Diano
Hippolyte et al., 1994 2 m high scarp estimated by eye towards Aulleta village (NW part of the Vallo di Diano fault) Irpinia 0.25-0.35 Pantosti et al., 1993 Trenching at the basin o f Piano di Pecore
recognized four pre-1980 paleoevents San Gregorio 0.3 D'Addezio et al.,
1991
Trenching on the NE dipping fault at San Gregorio basin four paleoevents were recognized
In Section 5.3.1.2, where a fault-by-fault description is presented, published throw-rates are presented in more detail and compared with the rates extracted from this study in order to offer a complete picture of the deformation rate pattern.
Some workers have estimated extension rates in southern Apennines based on seismic moment summation and geological slip rate values, but overall there are considerably fewer reports compared to the central Apennines. In particular, Pantosti et al., (1993), calculated an extension rate value of less than a 1 mm/yr, based on the slip rate extracted from the trench site on the Irpinia fault (0.25-0.35 mm/yr) and assumed that “a couple of parallel active faults” with the same slip-rate may exist across the Apennines. Westaway (1992) mentioned a value of 2.6 mm/yr, based on seismic moment summation for historical earthquakes and fault slip rate
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estimates. In Section 5.3.1.3.3, these extension rate hypotheses will be tested against geological fault throw-rates extracted from this study.
5.2 GEOMORPHOLOGICAL SETTING
In a similar manner to Lazio-Abruzzo (Section 4.2), several mountains in the southern Apennines show traces of former glaciations such as the Pollino Massif (2248m), Mount Sirino (2005m), Mount Cervati (1898m), Mount Cozzo del Pellegrino (1987m) and the Mount La Mula (1935m) (Palmentola et al., 1990). All the glacial remains (moraines, till deposits, cirques) belong to the last glacial maximum between 21-18 ka, when the snow line reached its lowest limit at about 1600-1750 m (Palmentola et al., 1990). Sediment cores obtained from Lago Grande di Monticchio in Basilicata, southern Apennines, demonstrated that the closely coupled Northern Hemisphere ocean-atmosphere system of the last glacial period, extended its influence as far as the central Mediterranean region (Allen et al., 1999). For the same area, Peyron et al. (1998) after reconstructing the climate of the last glacial maximum (18 ka), calculated a mean temperature anomaly of the coldest month of -14C° and an annual mean temperature anomaly of - 7C°. The above data also allow correlation with climatic records from Tyrrhenian sea cores and other oceanic records (Paterne et al., 1986; 1988; 1999), which also record the c. 18 ka culmination of the glacial maximum.
Deglaciation is a period of anomalously high ice flux and rapid basal ice motion resulting in high erosion rates (Menzies, 1996; Koppes and Hallet, 2002). However, during the last glacial maximum, most of the area of the southern Apennines, was not permanently covered by ice but experienced periglacial conditions with vigorous freeze-thaw action, providing a considerable amount of debris leading to high erosion-sedimentation rates on mountain slopes. Also mass movement and meltwaters from glaciers transported a large amount of glacial materials into neighbouring periglacial areas. In addition, the harsh climate restricted the vegetation, again promoting high erosion rates. As a result, sedimentation and erosion rates exceeded fault throw- rates, resulting in smoothed hillsides that are graded to the same gradient either side of fault scarps (e.g. Fig. 5.9i, Fig. 5.9ii, Fig. 5.9iii). These slopes have been preserved because after the demise of the glaciation, vegetation stabilised the mountain slopes and erosion rates decreased, producing a thin (c. 1-2 meters) organic rich soil. The lower erosion and sedimentation rates allowed the preservation of faults scarps produced by the ongoing surface fault slip during large earthquakes (e.g. 1980 Irpinia).
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In conclusion, the climatic history of the southern Apennines is similar to the neighbouring setting of the central Apennines, in Lazio-Abruzzo (Section 4.2), where fault scarps displace post-glacial sediments associated with the last major glacial retreat that occurred in the region 18 kyrs ago (Giraudi, 1995; Giraudi and Frezzotti, 1997). The vertical offset of the glacial surfaces corresponds to the total throw of the fault that has been accumulated since the end of the glaciation, allowing derivation of deformation rates.
5.3 FAULT DESCRIPTION, DEFORMATION RATES, FINITE THROWS AND DATA ANALYSIS
In Section 5.3.1, throw-rates and finite throw data are presented and then analysed in order to accomplice the goals presented in Section 5.1. Throw-rates represent the measured values derived from displaced post-glacial sediments through the construction of scarp profiles, whereas finite throws were extracted through the construction of cross sections. In Section 5.3.2, throw-rates are calculated from the equation presented by Cowie and Roberts (2001), which predicts throw-rates and then are compared with the measured throw-rates. The equation was described in detail in Section 2.6, and applied in Lazio-Abruzzo, central Italy in Section 4.3.2.
5.3.1 MEASURED DATA
This section is divided into three parts. In Section 5.3.1.1, a detailed description of the methodology used to derive throw-rates (5.3.1.1.1) and finite throws (5.3.1.1.2) is presented. In Section 5.3.1.2, a fault-by-fault description of the entire fault pattern in the southern Apennines is presented. Additionally, throw-rates and finite throws extracted from this study are combined and compared with published rates. In Section 5.3.1.3, the data presented in the previous Section, is analysed to unravel further implications on the hazard distribution, extension rates, fault initiation ages and the fault array evolution.
Table 5.2 summarizes all throw-rate and finite throw data collected during this study and the literature, which have been imported in the data analysis described in Section 5.3.1.3. All of these data (slope dips and slip directions) are presented in detail in Appendix B. In Table 5.2, the source of throw-rate data is distinguished, showing whether they are from scarp profiles (S.P.), or from eye-estimations (E.E.) or from published trench investigations (T.). Finally, maximum finite throws are presented in meters.