- Rome, Lazio, Italy
The Vallo di Diano is the largest Quaternary extensional basin in the southern Apennines thrust-belt axis (Italy). This portion of the chain is highly seismic and is currently subject to NE-extension, which triggers large (M> 6)... more
The Vallo di Diano is the largest Quaternary extensional basin in the southern Apennines thrust-belt axis (Italy). This portion of the chain is highly seismic and is currently subject to NE-extension, which triggers large (M> 6) normal-faulting earthquakes along NW-trending faults. The eastern edge of the Vallo di Diano basin is bounded by an extensional fault system featuring three main NW-trending, SW-dipping, right-stepping, ~15-17 km long segments (from north to south: Polla, Atena Lucana-Sala Consilina and Padula faults). Holocene activity has been documented so far only for the Polla segment. We have therefore focused our geomorphological and paleoseismological study on the southern portion of the system, particularly along the ~ 4 km long Atena Lucana-Sala Consilina and Padula faults overlap zone. The latter is characterized by a complex system of coalescent alluvial fans, Middle Pleistocene to Holocene in age. Here we recognized a > 4 km long and 0.5-1.4 km wide set of scarps (ranging in height between 1 m and 2.5 m) affecting Late Pleistocene - Holocene alluvial fans. In the same area, two Late Pleistocene volcanoclastic layers at the top of an alluvial fan exposed in a quarry are affected by ~ 1 m normal displacements. Moreover, a trench excavated across a 2 m high scarp affecting a Holocene fan revealed warping of Late Holocene debris flow deposits, with a total vertical throw of about 0.3 m. We therefore infer the overlap zone of the Atena Lucana-Sala Consilina and Padula faults is a breached relay ramp, generated by hard-linkage of the two fault segments since Late Pleistocene. This ~ 32 km long fault system is active and is capable of generating Mw ≥6.5 earthquakes.
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The statistical law for large earthquakes recurrence is still matter of debate. Although different and antithetical statistical distributions have been so far proposed, there is not a commonly accepted model yet. We argue that part of... more
The statistical law for large earthquakes recurrence is still matter of debate. Although different and antithetical statistical distributions have been so far proposed, there is not a commonly accepted model yet. We argue that part of these discrepancies is possibly related to the different time behavior of "individual seismogenic structure" and "seismic regions", the latter being composed by interacting structures. Here, we set a quantitative model based on a realistic interacting fault system to investigate on this issue. We define an active fault system in Central Italy that includes causative faults of moderate to large magnitude earthquakes. The main geometric and kinematic parameters of each structure are confidently assessed. Then, we study the evolution through time of the fault system by modeling different seismogenic processes and the interaction among faults by means of co- and post-seismic stress variations. The model produces synthetic catalogs on regional and sub-regional scale, as well as earthquake catalog for each seismogenic structure. The results highlight many interesting features: (i) the regional and sub-regional synthetic seismic catalogs reproduce the main characteristics of the real historical catalog of the last four centuries; (ii) the synthetic catalogs show significant long-term nonstationarity with seismic rates that vary on time scales different from the recurrence time of each fault; (iii) the statistical earthquake distribution on faults and on seismic regions are completely different. Finally, we interpret these results in terms of the physics of the process.
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ABSTRACT
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The deployment of a temporary seismic network in Southern Italy during 2001-2004 (the SAPTEX array, Southern APennine Tomography EXperiment) allowed us to relocate the hypocenters of Southern Apennines earthquakes with low uncertainty... more
The deployment of a temporary seismic network in Southern Italy during 2001-2004 (the SAPTEX array, Southern APennine Tomography EXperiment) allowed us to relocate the hypocenters of Southern Apennines earthquakes with low uncertainty among the location parameters. The best array distribution of the SAPTEX network for the analysis of seismicity in the Lucanian Apennines and foredeep was reached in the first two years of recording. The SAPTEX data were merged with those of the Italian National Seismic Network (RSNC) operated by the Istituto Nazionale di Geofisica e Vulcanologia (INGV). For the hypocenters computation of events in the upper Agri Valley we also included P- and S- waves arrivals from the local Eni-Agip network. The seismicity for the Lucanian Apennines and foredeep in the analyzed period has magnitudes ranging from 2.0 to 4.1. A major finding is the identification of two different crustal domains: the westernmost characterizing the chain, mostly with shallow earthquakes...
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The Sybaris town was founded by the Greeks in 720 B.C and its life went on up to the late Roman time (VI-VII century A.D.). The town was located within the Sibari Plain near the Crati River mouth (Ionian northern Calabria, southern... more
The Sybaris town was founded by the Greeks in 720 B.C and its life went on up to the late Roman time (VI-VII century A.D.). The town was located within the Sibari Plain near the Crati River mouth (Ionian northern Calabria, southern Italy). Sybaris occurs in area repeatedly affected by natural damaging phenomena, as frequent flooding, high local subsidence, marine storms, and earthquakes. The 2700 year long record of history of Sybaris stores the traces of these natural events and their influence on the human ancient environment through time. Among the natural disasters, we recognize two Roman age earthquakes striking the town. We isolate the damaging of these seismic events, set their time of occurrence, and map a shear zone crossing the site. These results were obtained through i) survey of coseismic features on the ruins, ii) geoarchaeological stratigraphy analysis, and TL and C14 dating, iii) analysis of high-resolution topographic data (1m pixel LiDAR DEM). The Sybaris town show...
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The occurrence of the Mw 6.3, April 6, 2009 earthquake has highlighted how critical is the development of hazard models that incorporate all the information on the long-term seismic behavior of faults (i.e., individual events rupture... more
The occurrence of the Mw 6.3, April 6, 2009 earthquake has highlighted how critical is the development of hazard models that incorporate all the information on the long-term seismic behavior of faults (i.e., individual events rupture length and slip, timing, etc.). Under this light we started a campaign of paleoseismological investigations in the epicentral area. The 2009 earthquake occurred on the Paganica normal fault (PF hereinafter) and produced a max 0.15 m high, 3 km-long continuous surface rupture along its central section, as well as several short, discontinuous cracks along the rest of the fault trace; secondary slip along nearby tectonic structures was observed too. The PF consists of a prominent NW-SE striking and SW dipping long-term morphologic scarp formed by the tectonic juxtaposition of Pliocene-middle Pleistocene and late Pleistocene alluvial deposits, and by smaller compound scarps in late Pleistocene-Holocene deposits. The fault runs for a total length of about 20 km along the NE side of the Aterno River valley, a graben-type basin bounded by marked antithetic faults. The limited extent and the small throw of the 2009 surface ruptures, when compared to the size of the Paganica long-term fault scarp, raise questions about the evolution and rupture history of this fault and suggest that the PF may have experienced larger Magnitude earthquakes than the 2009 seismic event. With the aim of defining the Max Magnitude expected for the PF by determining the size of the individual coseismic surface ruptures occurred in the past and their max extent, their frequency and the average rate of displacement we have been excavating new trenches and studied artificial exposures across the PF fault zone, in most of the cases intersecting the 2009 surface ruptures. Preliminary results show evidence for repeated decimetric surface faulting events during the past 3 millennia with the penultimate likely being the 1461 event (Me 6.4); evidence for possible previous larger slip events is found too. Whether the small ruptures are all related to slip at depth on the PF or would represent sympathetic slip triggered by earthquake occurred on nearby faults should be better investigated. Conversely, provided the "double size" slip behavior of the PF is confirmed, to characterize the seismic hazard of the area we should consider a more complex seismogenic model than that presently applied. In particular, we should include also the scenario that the PF produces relatively frequent (each 4-600 yr) 2009-type earthquakes and rare (each 3-4 millennia) larger events, likely in connection with other nearby active structures (i.e., San Demetrio Fault? Pettino Fault?).
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The Mw6.3, April 6, 2009 earthquake occurred on the previously identified Paganica normal fault and produced a 3 km-long co-seismic surface rupture along its northern section, with few centimeters of vertical displacement. Extensive... more
The Mw6.3, April 6, 2009 earthquake occurred on the previously identified Paganica normal fault and produced a 3 km-long co-seismic surface rupture along its northern section, with few centimeters of vertical displacement. Extensive 1:10,000-scale geological and geomorphological mapping has been carried out, focusing on the characterization of the long-term expression of the Paganica Fault at the surface. The field mapping was integrated by observations, made on 1:33,000 scale aerial photographs (GAI), 5-m-resolution Digital Elevation Model and standard morphometric derivatives (hill-shaded and slope angle maps, Spatial Analyst™). Particular attention was devoted to the study of the continental deposits and landforms affected by cumulative offset with the aim to reconstruct the Quaternary deformational history of the fault. The fault runs for a total length of 20 km and, along with antithetic faults on its hanging-wall, forms the graben of the Middle Aterno River Valley. The whole fault system and the variable setting of deformation affecting the continental deposits at the surface were identified. The Paganica long-term morphologic signature is represented by a set of prominent scarps formed by the tectonic juxtaposition of late Pliocene-middle Pleistocene and late Pleistocene alluvial deposits, and by lower scarps in late Pleistocene-Holocene deposits. In addition, evident Quaternary erosional and depositional paleosurfaces were recognized and sampled for 14C and OSL (Optically Stimulated Luminescence) and tephra chronology dating for long-term slip-rate calculations. This study resulted helpful to locate four paleoseismological investigations (see Pantosti et al. talk) and to provide the appropriate context for correctly interpret the depositional bodies outcropping on the trench walls. These paleoseismological investigations evidenced the presence of repeated late Pleistocene-Holocene activity and allowed for slip-rate estimation at a shorter time-scale. Such estimates were valuable for a comparison with the preliminary estimates on late Pleistocene calculations carried out by geomorphological investigations. Moreover, we correlated co-seismic deformations with the long-term morphologies and structures. The 2009 co-seismic ruptures show a general coherence with the long-term Paganica fault trace, both in terms of location and style. However, the limited extent of the 2009 surface ruptures coincides with the portion of the fault trace where deformation is more localized and few splays contribute to the extension. This is also testified by the presence on its hanging-wall of a large late Pleistocene-Holocene alluvial fan that subsides over the basin depocenter. Conversely, where the Paganica fault system branches out, various splays accommodated the small 2009 co-seismic throw, resulting in a distributed and not evident extensional strain. The preserved fault-related geomorphology is evidence for the persistence of the rupture complexities during Quaternary. On this light, further studies on the style of fault activity are needed to estimate if the Paganica fault is capable of earthquakes with Magnitude larger than the 2009 event.
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The Pollino Range area represents the mostprominent gap in seismicity within thesouthern Apennines. Geomorphic andtrenching investigations along theCastrovillari fault indicate that thisnormal fault is a major seismogenic faultwithin the... more
The Pollino Range area represents the mostprominent gap in seismicity within thesouthern Apennines. Geomorphic andtrenching investigations along theCastrovillari fault indicate that thisnormal fault is a major seismogenic faultwithin the southern part of this gap. Atleast four surface-faulting earthquakeshave occurred on this fault since latePleistocene age. Radiocarbon dating coupledwith historical consideration set thetime of the most recent earthquake as mostlikely to be between 530 A.D. and 900 A.D.,with the possible widest interval of530–1100 A.D. No evidence for this eventhas been found in the historical records,although its age interval falls within thetime spanned by the seismic catalogues.Slip per event ranges between 0.5 and1.6 m, with a minimum rupture length of13 km. These values suggest a M 6.5–7.0 forthe paleoearthquakes. The minimum long-termvertical slip rate obtained from displacedgeomorphic features is of 0.2–0.5 mm/yr. Avertical slip-rate of about 1 mm/yr is alsoinferred from trenching data. Theinter-event interval obtained from trenchdata ranges between 940 and 7760 years(with the young part of the intervalpossibly more representative; roughly940–3000 years). The time elapsed since themost recent earthquake ranges between aminimum of 900–1100 and a maximum of 1470years. The seismic behavior of this faultappears to be consistent with that of othermajor seismogenic faults of thecentral-southern Apennines. The Pollinocase highlights the fact thatgeological investigations represent apotentially useful technique tocharacterize the seismic hazard of `silent' areas for which adequate historical andseismological data record are notavailable.
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We studied fault scarps along the northern sector of the Celano-L'Aquila fault system in the Abruzzi region (central Apennines). Up to ~9.5 km long, 3 m high, fault scarp traces mark the slope foot of ridgetop valleys at Mt Ocre range. In... more
We studied fault scarps along the northern sector of the Celano-L'Aquila fault system in the Abruzzi region (central Apennines). Up to ~9.5 km long, 3 m high, fault scarp traces mark the slope foot of ridgetop valleys at Mt Ocre range. In order to provide direct evidence of the deformation history of these scarps, we initiated geomorphic, ground-penetrating radar (GPR) and trenching investigations. GPR investigations yielded subsurface stratigraphic features of the scarp zones, and determined the locations for trenching sites. A total of five trenches were excavated at two different sites. Structural and stratigraphic analysis of the trench exposures combined with historical considerations, showed three faulting events between 5620 BC and 1300 AD; the most recent of them occurred after 1690 BC. Each of these events produced an estimated minimum vertical displacement ranging between 0.3 and 0.5 m. Our interpretation is that the Mt Ocre fault branch represents the northernmost surface expression of a single 35 km long seismogenic structure associated with M~ 7 earthquakes. Any attempt to estimate the seismic hazard in the area must consider the presence of this important source.
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... I Regional uplift and local tectonic deformation recorded by the Quaternary marine terraces on the Ionian coast of northern Calabria (southern Italy) Luigi Cucci *, Francesca R. Cinti lstituto ... In: Boriani, A., Bonafede, M.,... more
... I Regional uplift and local tectonic deformation recorded by the Quaternary marine terraces on the Ionian coast of northern Calabria (southern Italy) Luigi Cucci *, Francesca R. Cinti lstituto ... In: Boriani, A., Bonafede, M., Piccardo, GB, Vai, GB (Eds.), The Lithosphere in Italy. ...
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Large historical earthquakes in Italy define a prominent gap in the Pollino region of the southern Apennines. Geomorphic and palaeoseismological investigations in this region show that the Castrovillari fault (CF) is a major seismogenic... more
Large historical earthquakes in Italy define a prominent gap in the Pollino region of the southern Apennines. Geomorphic and palaeoseismological investigations in this region show that the Castrovillari fault (CF) is a major seismogenic source that could potentially fill the southern part of this gap. The surface expression of the CF is a complex, 10–13 km long set of prominent scarps. Trenches across one scarp indicate that at least four surface-faulting earthquakes have occurred along the CF since Late Pleistocene time, each producing at least 1 m of vertical displacement. The length of the fault and the slip per event suggest M=6.5-7.0 for the palaeoearthquakes. Preliminary radiocarbon dating coupled with historical considerations imply that the most recent of these earthquakes occurred between 380 BC and 1200 AD, and probably soon after 760 AD; no evidence for this event has been found in the historical record. We estimate a minimum recurrence interval of 1170 years and a vertical slip rate of 0.2-0.5 mm yr-1 for the CF, which indicates that the seismic behaviour of this fault is comparable to other major seismogenic faults of the central-southern Apennines. The lack of mention or the mislocation of the most recent event in the historical seismic memory of the Pollino region clearly shows that even in Italy, which has one of the longest historical records of seismicity, a seismic hazard assessment based solely on the historical record may not be completely reliable, and shows that geological investigations are critical for filling possible information gaps.
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We classified the most outstanding rupturesof the 1997 Umbria-Marche seismic sequence assecondary tectonic effects that occur within the zoneof deformation induced by the deep displacement on theseismogenic structure. The trend of the... more
We classified the most outstanding rupturesof the 1997 Umbria-Marche seismic sequence assecondary tectonic effects that occur within the zoneof deformation induced by the deep displacement on theseismogenic structure. The trend of the surfacedeformation is homogeneous within the entire area ofinterest and consistent with NE-oriented extensionevidenced by CMT focal solutions of the three mainshocks. We extrapolate the discontinuous sites ofbreak measurements and suggest that the localdeformation concentrates along four narrow bands.Location and direction of these bands are locallycontrolled by pre-existing structures. The comparisonbetween our data with the seismological data – such asmain rupture planes and spatial aftershockdistribution – highlights that three bands mark partof the boundaries of the NW-SE elongated aftershocksarea and the fourth occurs where this area is widest.Moreover, the analysis of the structural setting ofthe area suggests that N-S shear zones have stronglycontrolled the extension of the main rupture segmentsand the aftershock distribution. The surface rupturesare located within the area of coseismic deformationresulting from DInSAR data; we propose that theyrepresent the localized response to the verticalground deformation of the area. Finally, we discussthe contribution of the pattern of the 1997 surfacebreaks to the characterization of the seismogenicsource.
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A high-resolution digital elevation model (DEM, 1 ms spacing) derived from an airborne light detection and ranging (LiDAR) campaign was used in an attempt to characterize the structural and erosive elements of the geometry of the Pettino... more
A high-resolution digital elevation model (DEM, 1 ms spacing) derived from an airborne light detection and ranging (LiDAR) campaign was used in an attempt to characterize the structural and erosive elements of the geometry of the Pettino fault, a seismogenic normal fault in Central Apennines (Italy). Four 90- to 280 m-long fault scarp segments were selected and the surface between the base and the top of the scarps was analyzed through the statistical analysis of the following DEM-derived parameters: altitude, height of the fault scarp, and distance along strike, slope, and aspect. The results identify slopes of up to 40° in faults lower reaches interpreted as fresh faces, 34° up the faces. The Pettino fault maximum long-term slip rate (0.6–1.1 mm/yr) was estimated from the scarp heights, which are up to 12–19 m in the selected four segments, and the age (ca. 18 ka) of the last glacial erosional phase in the area. The combined analysis of the DEM-derived parameters allows us to (a) define aspects of three-dimensional scarp geometry, (b) decipher its geomorphological significance, and (c) estimate the long-term slip rate.
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The Mw6.3, April 6, 2009 earthquake occurred on the previously identified Paganica normal fault and produced a 3 km-long co-seismic surface rupture along its northern section, with few centimeters of vertical displacement. Extensive... more
The Mw6.3, April 6, 2009 earthquake occurred on the previously identified Paganica normal fault and produced a 3 km-long co-seismic surface rupture along its northern section, with few centimeters of vertical displacement. Extensive 1:10,000-scale geological and geomorphological mapping has been carried out, focusing on the characterization of the long-term expression of the Paganica Fault at the surface. The field mapping was integrated by observations, made on 1:33,000 scale aerial photographs (GAI), 5-m-resolution Digital Elevation Model and standard morphometric derivatives (hill-shaded and slope angle maps, Spatial Analyst™). Particular attention was devoted to the study of the continental deposits and landforms affected by cumulative offset with the aim to reconstruct the Quaternary deformational history of the fault. The fault runs for a total length of 20 km and, along with antithetic faults on its hanging-wall, forms the graben of the Middle Aterno River Valley. The whole fault system and the variable setting of deformation affecting the continental deposits at the surface were identified. The Paganica long-term morphologic signature is represented by a set of prominent scarps formed by the tectonic juxtaposition of late Pliocene-middle Pleistocene and late Pleistocene alluvial deposits, and by lower scarps in late Pleistocene-Holocene deposits. In addition, evident Quaternary erosional and depositional paleosurfaces were recognized and sampled for 14C and OSL (Optically Stimulated Luminescence) and tephra chronology dating for long-term slip-rate calculations. This study resulted helpful to locate four paleoseismological investigations (see Pantosti et al. talk) and to provide the appropriate context for correctly interpret the depositional bodies outcropping on the trench walls. These paleoseismological investigations evidenced the presence of repeated late Pleistocene-Holocene activity and allowed for slip-rate estimation at a shorter time-scale. Such estimates were valuable for a comparison with the preliminary estimates on late Pleistocene calculations carried out by geomorphological investigations. Moreover, we correlated co-seismic deformations with the long-term morphologies and structures. The 2009 co-seismic ruptures show a general coherence with the long-term Paganica fault trace, both in terms of location and style. However, the limited extent of the 2009 surface ruptures coincides with the portion of the fault trace where deformation is more localized and few splays contribute to the extension. This is also testified by the presence on its hanging-wall of a large late Pleistocene-Holocene alluvial fan that subsides over the basin depocenter. Conversely, where the Paganica fault system branches out, various splays accommodated the small 2009 co-seismic throw, resulting in a distributed and not evident extensional strain. The preserved fault-related geomorphology is evidence for the persistence of the rupture complexities during Quaternary. On this light, further studies on the style of fault activity are needed to estimate if the Paganica fault is capable of earthquakes with Magnitude larger than the 2009 event.