Use of point scale models to improve conceptual understanding in complex aquifers: An example from a sandstone aquifer in the Eden valley,Cumbria, UK

Understanding catchment functioning is increasingly important to enable water resources to be quantified and used sustainably, flood risk to be minimized, as well as to protect the system from degradation by pollution. Developing conceptual understanding of groundwater systems and their encapsulation in models is an important part of this understanding, but they are resource intensive to create and calibrate. The relative lack of data or the particular complexity of a groundwater system can prevent the development of a satisfactory conceptual understanding of the hydrological behaviour, which can be used to construct an adequate distributed model. A time series of daily groundwater levels from the Permo-Triassic sandstones situated in the River Eden Valley, Cumbria, UK have been analysed. These hydrographs show a range of behaviours and therefore have previously been studied using statistical and time series analysis techniques. This paper describes the application of AquiMOD, impulse response function (IRF) and combined AquiMOD-IRF methods to characterize the daily groundwater hydrographs. The best approach for each characteristic type of response has been determined and related to the geological and hydrogeological framework found at each borehole location. It is clear that AquiMOD, IRF and a combination of AquiMOD with IRF can be deployed to reproduce hydrograph responses in a range of hydrogeological settings. Importantly the choice of different techniques demonstrates the influence of differing processes and hydrogeological settings. Further they can distinguish the influences of differing hydrogeological environments and the impacts these have on the groundwater flow processes. They can be used, as shown in this paper, in a staged approach to help develop reliable and comprehensive conceptual models of groundwater flow. This can then be used as a solid basis for the development of distributed models, particularly as the latter are resource expensive to build and to calibrate effectively. This approach of using simple models and techniques first identifies specific aspects of catchment functioning, for example influence of the river, that can be later tested in a distributed model.     

3-D density model of Mt. Etna Volcano (Southern Italy)

A detailed density model of Mt. Etna and its surrounding areas has been evaluated using a 3-D inversion of the gravimetric data acquired in the 1980's. Several high-density and low-density bodies are found, penetrating from shallow depths as far down as 12 km bsl. A positive correlation (in terms of location, extent, density, and velocity) is established between several anomalies of the density model and features identified in previously published seismic tomographies. A prominent high-density body extending down to 7 km bsl is recognized in the southern part of the Valle del Bove, and interpreted as a solidified magmatic intrusion. On the western boundary of this anomaly, a low-density body is interpreted as a bubble and liquid magma mixture. Outside the central area, three other high-density anomalies are imaged and attributed to the earliest phases of volcanic activity in the area. Several interesting low-density anomalies are also identified and correlated with known fault lines and other structural features of the region.     

The effect of low‐permeability fault zones on groundwater flow in a compartmentalized system. Experimental evidence from a carbonate aquifer (Southern Italy)

The hydrogeological behaviour of fault zones in carbonate aquifers is often neglected in conceptual and numerical models. Furthermore, no information is available regarding the relationships between piezometric levels when significant compartmentalization occurs due to the occurrence of low‐flow fault zones. The aim of this study was to refine the conceptualization of subsurface flow in faulted carbonate aquifers and to analyse relationships between sub‐basins within a compartmentalized aquifer system in Southern Italy. The interactions between compartments that straddle low‐flow faults were investigated over four hydrologic years using a statistical approach to compare (i) the hydraulic heads within two wells located up‐ and down‐gradient of tectonic discontinuities as well as (ii) the rainfall and piezometric levels. The results of this study suggest that a set of barriers exists between the wells, and, therefore, the total head loss observed between the wells (approximately 80 m) should be distributed across several aquitards, with one aquitard exhibiting a relatively high permeability or low degree of integrity. Due to slight differences in permeability, transient conditions in aquitards can occur over relatively short periods, which is in agreement with the results of the statistical data analysis. Consequently, rather than being caused by pure aquitards, aquifer system compartmentalization likely results from slight differences in the permeability between lower‐permeability fault zones and adjacent higher‐permeability protoliths. Copyright © 2014 John Wiley & Sons, Ltd.     

A thermal model of the magma reservoir feeding Plinian eruptions at Mt. Vesuvius (Italy)

A theoretical thermal model has been worked out for the magma reservoir that would have fed the two last Plinian eruptions of Mt. Vesuvius (Barberi et al., 1981). The effect of convective motions is discussed, and it is shown that the size of convective cells and the efficiency of the process in smoothing out temperature gradients evolves in time due to the progressive viscosity increase produced by the heat lost by conductive heat transfer through the host rock. Although convection will be important throughout the history of the reservoir, until very high viscosities are reached, the pure conductive model seems to account satisfactorily for the cumulative heat loss by the reservoir. Gravitative crystal settling can occur, even in presence of convective motions, mostly during several hundred years after the magma emplacement when viscosity is not yet increased to high values.     

Geochemistry of water and gas discharges from the Mt. Amiata silicic complex and surrounding areas (central Italy)

The Mt. Amiata volcano in central Italy is intimately related to the post-orogenic magmatic activity which started in Pliocene times. Major, trace elements, and isotopic composition of thermal and cold spring waters and gas manifestations indicate the occurrence of three main reservoir of the thermal and cold waters in the Mt. Amiata region. The deepest one is located in an extensive carbonate reservoir buried by thick sequences of low-permeability allochthonous and neo-autochthonous formations. Thermal spring waters discharging from this aquifer have a neutral Ca-SO₄ composition due to the presence of anhydrite layers at the base of the carbonate series and, possibly, to absorption of deep-derived H₂S with subsequent oxidation to SO₄²⁻ in a system where pH is buffered by the calcite–anhydrite pair (Marini and Chiodini, 1994). Isotopic signature of these springs and N₂-rich composition of associated gas phases suggest a clear local meteoric origin of the feeding waters, and atmospheric O₂ may be responsible for the oxidation of H₂S. The two shallower aquifers have different chemical features. One is Ca-HCO₃ in composition and located in several sedimentary formations above the Mesozoic carbonates. The other one has a Na-Cl composition and is hosted in marine sediments filling many post-orogenic NW–SE-trending basins. Strontium, Ba, F, and Br contents have been used to group waters associated with each aquifer. Although circulating to some extent in the same carbonate reservoir, the deep geothermal fluids at Latera and Mt. Amiata and thermal springs discharging from their outcropping areas have different composition: Na-Cl and Ca-SO₄ type, respectively. Considering the high permeability of the reservoir rock, the meteoric origin of thermal springs and the two different composition of the thermal waters, self-sealed barriers must be present at the boundaries of the geothermal systems. The complex hydrology of the reservoir rocks greatly affects the reliability of geothermometers in liquid phase, which understimate the real temperatures of the discovered geothermal fields. More reliable temperatures are envisaged by using gas composition-based geothermometers. Bulk composition of the 67 gas samples studied seems to be the result of a continuous mixing between a N₂-rich component of meteoric origin related to the Ca-SO₄ aquifer and a deep CO₂-rich component rising largely along the boundaries of the geothermal systems. Nitrogen-rich gas samples have nearly atmospheric N₂/Ar (=83) and

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(δ=0‰) ratios whereas CO₂-rich samples show anomalously high

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values (up to +6.13 ‰), likely related to N₂ from metamorphic schists lying below the carbonate formations. On the basis of average

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isotopic ratio (

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around 0‰), CO₂ seems to originate mainly from thermometamorphic reactions in the carbonate reservoir and/or in carbonate layers embedded in the underlying metamorphic basement. Distribution of

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isotopic ratios indicates a radiogenic origin of helium in a tectonic environment that, in spite of the presence of many post-orogenic basins and mantle-derived magmatics, can presently be considered in a compressive phase.     

Debris flow and slide deposits at the top of the Internal Liguride ophiolitic sequence, Northern Apennines, Italy: A record of frontal tectonic erosion in a fossil accretionary wedge

Abstract In the Northern Apennines, the Internal Liguride units are characterized by an ophiolite sequence that represents the stratigraphic base of a late Jurassic–early Paleocene sedimentary cover. The Bocco Shale represents the youngest deposit recognized in the sedimentary cover of the ophiolite and can be subdivided into two different groups of deep sea sediments. The first group is represented by slide, debris flow and high density turbidity current-derived deposits, whereas the second group consists of thin-bedded turbidites. Facies analysis and provenance studies indicate, for the former group, small and scarcely evoluted flows that rework an oceanic lithosphere and its sedimentary cover. We interpret the Bocco Shale as an ancient example of a deposit related to the frontal tectonic erosion of the accretionary wedge slope. The frontal tectonic erosion resulted in a large removal of materials, from the accretionary wedge front, that was reworked as debris flows and slide deposits sedimented on the lower plate above the trench deposits. The frontal tectonic erosion was probably connected with subduction of oceanic crust characterized by positive topographic relief. This interpretation can be also applied for the origin of analogous deposits of Western Alps and Corsica.     

Geochemical signatures of large active faults: The example of the 5 February 1783, Calabrian earthquake (southern Italy)

Five large earthquakes shook southern Calabria in February–March 1783. We focused on the first shock (M_e 6.9), which occurred on 5 February in the Gioia Tauro Plain. Most investigators attribute the event to a W-dipping, high-angle fault running at the base of the Aspromonte crystalline bedrock on the ESE side of the Plain (Aspromonte Fault). Other workers contend that the earthquake was generated by an E-dipping, low-angle blind fault (Gioia Tauro Fault) similar to the adjacent Messina Straits Fault. In 1999–2000 we carried out four geochemical surveys in the Gioia Tauro Plain with the aim of contributing to this debate with an independent line of evidence. We sampled 240 groundwater sites and measured a suite of in-situ physical and chemical parameters. Our goal was to gain new insight into the seismogenic source by identifying geochemical anomalies associated with the deepening of the hydrological circuits due to the presence of enhanced faulting/fracturing. The deep-fluid signatures are mainly represented by temperature, salinity, total carbon and radon anomalies. We identified three zones of dominant deep fluid discharge: the Nicotera-Galatro area (along the Nicotera-Galatro portion of the NW-trending Nicotera-Gioiosa Jonica lineament), a small NW-SE trending area between Gioia Tauro and Seminara, and the coastline between Rosarno and Palmi. This latter sector locates just above the upper edge of the hypothesised Gioia Tauro Fault. Most of the geochemical anomalies are recorded around Rosarno, at the intersection between the Gioia Tauro Fault and the Nicotera-Gioiosa Jonica lineament. In contrast, no evidence of groundwater deepening and active fracturing was found along the Aspromonte Fault. Based on our new findings we updated the concepts of Geochemically Active Fault Zone and Geochemical Interaction Fault Zone in view of the modern understanding of the hydro-mechanical properties of fault zones and the faulting mechanisms promoting fracture permeability in the crust.     

Resistivity imaging of Pleistocene alluvial aquifers in a contractional tectonic setting: A case history from the Po plain (Northern Italy)

In this work we present the hydrogeophysical imaging of a key sector of the Quaternary Po foreland basin (northern Italy), focussing on the reconstruction of clastic aquifers and aquitards in a complex tectono-sedimentary subsurface architecture. The study area includes the relic reliefs of Casalpusterlengo and Zorlesco, two smooth morphological features involving uplifted and gently folded Pleistocene marine to alluvial sediments, plausibly linked to the buried Northern Apennines thrust and fold belt. The geophysical data include 35 Direct Current Vertical Electrical Soundings collected over a 37 km² wide area, acquired with Schlumberger array and maximum half-spacing of 500 m. 1-D resistivity-depth profiles were computed for each VES. An integrated hydrostratigraphic approach was applied, to constrain the interpretation of the geophysical data along several cross-sections, including the comparison of resistivity soundings to stratigraphic logs, borehole electric logs and the pore-water properties.The resistivity interfaces, traceable with the same laterally continuous vertical polarity, were used to develop an electrostratigraphic model in order to portray the stacking of electrostratigraphic units down to 200 m below ground surface. Their vertical associations show a general upward increase of electrical resistivity. This assemblage mimics the regional coarsening upwards depositional trend, from the conductive units of the Plio-Pleistocene marine-to-transitional depositional systems to the resistive units of the Middle–Late Pleistocene fluvial and alluvial plain depositional systems. Middle Pleistocene depositional systems host an alternation of North-dipping, high-to-intermediate permeability aquifer systems (70–180 Ωm, thickness of 5–70 m) separated by low permeability aquitards (20–50 Ωm, thickness up to 40 m). These units pinch out against the Casalpusterlengo and Zorlesco relic reliefs, where they cover the uplifted and folded regional aquitard (20–50 Ωm) formed by Pliocene-Lower Pleistocene clays to sandy silts with gravel lenses in agreement with borehole data. In the deepest part of the local stratigraphy, a broad low-resistivity anomaly (< 10 Ωm) was clearly mapped through the study area. By comparison with electrical borehole logs in deep oil-wells, it could be interpreted as the fresh–saltwater interface due to the presence of connate waters and brines hosted by the marine-to-transitional shales.     

Eruption style and petrology of a new carbonatitic suite from the Mt. Vulture Southern Italy/: The Monticchio Lakes Formation

The Monticchio Lakes Formation MLF is a newly identified carbonatite-melilitite tuff sequence which is exposed in the southwestern sector of the Vulture volcano. It is the youngest example ca. 0.13 m.y. of this type of volcanism in Italy, although other carbonatites of smaller volume, but with similar characteristics, have been discovered recently. This volcanic event occurred in isolation after a 0.35 m.y. period of inactivity at Vulture. The eruption produced two maar-type vents and formed tuff aprons mainly composed of dune beds of lapilli. Depositional features suggest that a dry surge mechanism, possibly triggered by CO₂ expansion, was dominant during tuff emplacement. The MLF event involved a mixture of carbonatite and melilitite liquids which were physically separated before the eruption. Abundant mantle xenoliths are direct evidence of the deep-seated origin of the parental magma and its high velocity of propagation towards the surface. Often, these nodules form the core of lapilli composed of concentric shells of melilitite andror porphyritic carbonatite. Coarse-ash beds alternate with lapilli beds and consist of abundant lumps and spherulae of very fine-grained calcite immersed in a welded, highly compacted carbonatite matrix. Porphyritic carbonatite shells of the lapilli and fine-grained spherulae of calcite in the tuff matrix suggest incipient crystallisation of a carbonatite liquid in subvolcanic conditions and eruption of carbonatite-spray droplets. Dark coloured juvenile fragments mainly consist of melilite, phlogopite, calcite, apatite, perovskite, and häuyne crystals in a carbonatite or melilitite matrix. The rocks have an extremely primitive, ultramafic composition with very high Mga) 85. and Cr and Ni content 1500 ppm-. The calcite contains high SrO, BaO and REE of up to 1.5 wt.%. Similar compositions are typical of primary, magmatic carbonates which are found in both intrusive and extrusive carbonatites. The high modal Sr-Ba-REE-rich calcite, the typical mineralogy, and the high amount of Sr-group elements identify the carbonate component as a carbonatite. The very high Mga, mantle debris and C, O, He isotope ratios in the range of mantle values indicate a near-primary character for the carbonatite which is distinctive of a restricted group of extrusive carbonatites only found in continental rift areas.     

Structural setting of the Southern Apennine fold-and-thrust belt (Italy) at hypocentral depth: The Calore Valley case history

The reconstruction of the main structural features of the Southern Apennines (Italy), in correspondence with the focal volume of some strong earthquakes that have affected this chain, can be attempted by analysing reflection seismic lines and deep well logs in comparison with surface geology.For instance, the Calore Valley and its surroundings have been the object of intense hydrocarbon exploration, and a wealth of subsurface data is available. Moreover, this area was affected by the 1688 Sannio earthquake (macroseismic magnitude 7.1), and a new location has recently been proposed for the related causative fault system. The present work defines the structural setting of the Southern Apennine chain in correspondence with this new location, and compares it with similar cases along the Italian peninsula.The analysis was focussed on the reconstruction of deep tectonic units (formed by the buried Apulia carbonate platform succession), which generally correspond to the hypocentral depths of strong earthquakes along the axis of the Southern Apennines. The results show that the Apulia platform succession is affected by three main thrusts, locally accompanied by backthrusts. The top of this succession is relatively shallow: the maximum depth does not exceed 1.8 s TWT (i.e. about 3500 m b.s.l.), while minimum depths occur in correspondence with the ramp anticlines culminations, at 0.5 s TWT (i.e. at about 500 m b.s.l.). Moreover, data suggest that the underlying Paleozoic basement is possibly involved in thrusting.In a regional perspective, extensional seismogenic structures along the axis of the Southern Apennines seem to share some common characteristics. Indeed, they develop (i) in correspondence with an uplifted Paleozoic basement; (ii) at the rear of a set of thrusts that account for the shallow Apulia units; (iii) at the surface, in proximity to the leading edge of a surficial tectonic unit formed by the Apennine carbonate platform succession. The 1688 seismogenic fault system fits in with these common traits. In the light of this, we finally speculate that these common characteristics in the architecture of the chain could provide a key to the location of the major seismicity along the axis of the Southern Apennines and an interpretative model for the identification of possible areas of seismic gap in this part of the Italian peninsula.     

Identifying and characterizing solution conduits in karst aquifers through geospatial (GIS) analysis of porosity from borehole imagery: An example from the Biscayne aquifer,South Florida (USA)

We apply geospatial analysis to borehole imagery in an effort to develop new techniques to evaluate the spatial distribution and internal structure of karst conduits. Remote sensing software is used to classify a high resolution, digital borehole image of limestone bedrock from the Biscayne aquifer (South Florida, USA) into a binary image divided into cells of rock matrix and pores. Within a GIS, 2D porosity is calculated for a series of rectangular sampling windows placed over the binary image and then plotted as a function of depth. Potential conduits that intersect the borehole are identified as peaks of high porosity. A second GIS technique identifies a conduit as a continuous object that spans the entire borehole width. According to these criteria, geospatial analysis reveals ∼10 discrete conduits along the ∼15 m borehole image. Continuous sampling of the geologic medium intersected by the borehole provides insight into the internal structure of karst aquifers and the evolution of karst features. Most importantly, this pilot study demonstrates that GIS-based techniques are capable of quantifying the depths, dimensions, shapes, apertures and connectivity of potential conduits, physical attributes that impact flow in karst aquifers.     

Calibration of snow parameters in SWAT: comparison of three approaches in the Upper Adige River basin (Italy)

The Soil and Water Assessment Tool (SWAT) model is generally applied in alpine catchments using a unique set of snow parameters for the entire basin, and calibration is based on discharge records only. This technical note presents three calibration procedures for snow parameters of SWAT considering snow water equivalent (SWE) values computed using a dense network of snow depth measurement stations available in the Upper Adige River basin, Italy. The first two procedures calibrate snow parameters according to the average sub-basin SWE: the first one defines a unique set of parameters for the entire basin, while the second allows for sub-basin variability. The last approach includes the elevation band SWE output in the calibration for each sub-basin and qualitatively compares it to the SWE computed from the available snow depth monitoring stations. This last method provides the best agreement between SWAT model results and SWE data.     

The 1997 Umbria-Marche earthquakes (Italy): relation between the surface tectonic breaks and the area of deformation

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.     

The earthquake of 6 September 2002 and the seismic history of Palermo (Northern Sicily,Italy): Implications for the seismic hazard assessment of the city

On September 6, 2002, a M_L = 5.6 earthquake, occurring some tens of kilometres offshore from the Northern Sicilian coast (Southern Tyrrhenian Sea), slightly damaged the city of Palermo and surroundings (degree 6 in the European Macroseismic Scale 1998). The macroseismic investigation of the shock and a detailed study of effects of the main earthquakes which affected Palermo in the past have been performed in order to evaluate the seismic response of the city. Moreover, the comparison of the recent event, which is instrumentally constrained, with historical earthquakes allows us to infer new insights on the seismogenic sources of the area, that seem located offshore in the Tyrrhenian sea.In the last 500 years, Palermo has never been completely destroyed but has suffered effects estimated between intensities 6 and 8 EMS-98 many times (1693, 1726, 1751, 1823, 1940, 1968, 2002). The damage scenarios of the analysed events have shown that damage distribution is strongly conditioned by soil response in the different parts of the city and by a high building vulnerability, mainly in the historical centre and in the south-eastern zone of the modern city. As a matter of fact, Palermo has always suffered greater effects than those reported for other nearby localities. The hazard assessment obtained using observed site intensities has shown that the probability of occurrence for intensity 8 (the strongest intensity observed in Palermo) exceeds 99% for 550 years, while the estimated mean return period is 152 ± 40 years. These results, in connection with building vulnerability due to the urban expansion before the introduction of seismic code, suggest that the city is exposed to a relatively high seismic risk.This paper has not been submitted elsewhere in identical or similar form, nor will it be during the first 3 months after its submission to Journal of Seismology.     

Temporal Variability of Major and Trace Element Concentrations in the Groundwaters of Mt. Etna (Italy): Effects of Transient Input of Magmatic Fluids Highlighted by Means of Cluster Analysis

Data for major, minor and trace elements in groundwaters from Mt. Etna volcano collected in 1994, 1995 and 1997 were analyzed using Cluster Analysis (CA). Two groups of sampling sites were identified (named clusters A and B), mainly on the basis of their different salinity and content of dissolved CO₂. The highest levels of both of these parameters were observed in the sites of cluster A, located in the lower south-western and central eastern flanks of the volcano. For both of the statistical groups CA was repeated, taking into account the mean values of each parameter in time, and the results allowed us to recognize four distinct groups of parameters for each group of sites on the basis of their temporal patterns. Four different types of temporal patterns were recognized: concave, convex, increasing, decreasing. The observed changes were basically interpreted as a result of the different response of dissolved chemical elements to changes in the aqueous environment and/or in their solubility/mobility in water due to different rates of input of magmatic gases to Etna’s aquifers. The main changes occurred in 1995, when Etna’s volcanic activity resumed after a two-year period of rest. The temporal changes of the majority of the studied parameters (water temperature, water conductivity, Eh, pH, Al, Mg, B, Ca, Cl⁻, Hg, Mn, Mo, Na, Ni, Se, Si, Sr, Cr Zn and pCO₂) were not cluster-dependent, therefore they were not apparently affected by differences in water salinity between the two groups of sampling sites. A limited number of parameters (Ti, K, Li, HCO₃⁻, As, Fe, SO₄²⁻, Cu and V), however, manifested different behaviors, depending on the cluster of sites to which they belonged, thus suggesting their apparent dependency on water salinity.     

Upwards migration of seismic focii: A forerunner of the 1989 eruption of Mt Etna (Italy)

Data from a portable array of three-component digital stations, run at Mt Etna from 1988 to early 1990, highlight the seismic behaviour of the volcano before the 1989 eruption, one of the most significant in terms of energy of the last two decades. After a two-year period of weak and discotinuous seismicity, the depth of the seismically active volumes was observed to become shallower a few months before the volcanic event. The overall migration of the events, inferred by hypocentral locations and decreases of S-P time differences at two stations, agrees with other geophysical forerunners and allows further insights into the changes in the stress field leading to the eruption.     

The 1627 Gargano earthquake (Southern Italy): Identification and characterization of the causative fault

We present the results of a study of the subsurface tectonic features of the Basso Molise, Western Gargano and Northern Capitanata regions (Southern Italy) aimed at the identification of the source of the disastrous 1627 Gargano earthquake. In the maximum-damage area of this earthquake we have recognised a normal fault, here called the Apricena Fault, which has been identified as the fault that caused the seismic event. The Apricena Fault, striking WNW-ESE and dipping towards SSW, extends in the subsurface for about 30 kilometres from Serracapriola to Santa Maria di Stignano cutting through the whole Quaternary sequence. Other important tectonic structures trending WNW-ESE recognized in the area belong to an inactive Pleistocene strike-slip-fault system that is linked to the Mattinata Fault and to its offshore continuation in the Gondola-Grifone structural high. The Mattinata Fault and the Gondola-Grifone High form a quite complex structural feature whose kinematic behaviour is still matter of debate in the regional geological literature. NW-SE structural features recognized in the area are extensional faults whose activity was probably related to the late flexure-hinge retreat of the Adria plate margin during the Late Pliocene-Early Pleistocene eastward migration of the thrust belt-foredeep-foreland system.     

High precision locations of multiplets on south-eastern flank of Mt. Etna (Italy): reconstruction of fault plane geometry

On 9 January 2001, a seismic swarm, located on the south-eastern flank of Mt. Etna and with nearly identical waveforms, caused some damage to Zafferana Etnea village, 3 km from the epicentral area.An analysis of the seismicity occurring in the last 8 years in this area has revealed other earthquakes with the same characteristics; some pre-empted and followed (up to a few months) the 2001 January swarm, others were recorded more than five years beforehand.Using similarity of waveforms, these earthquakes were classified into three families.The use of a multiplet-technique has allowed to obtain the spatial distribution of the events with higher precision (mean error of 10-20 m) with respect to traditional localization techniques.Mt. Etna earthquakes relocation clearly describes the geometry of the seismogenic tectonic structure; the hypocenters lie on a NE-SW oriented plane that is coincident with one of the focal planes obtained by first-arrival polarities. This alignment is also coherent with one of the main regional tectonic trends cutting the Mt. Etna area, and can be interpreted as a right-lateral strike seismic source on the south-eastern flank of Mt. Etna, distant from eruptive centres, which repeats from time to time and is able to produce strong energy releases.     

Geomorphic response to late Quaternary tectonics in the axial portion of the Southern Apennines (Italy): A case study from the Calore River valley

The present study focuses on the morphotectonic evolution of the axial portion of the Southern Apennine chain between the lower Calore River valley and the northern Camposauro mountain front (Campania Region). A multidisciplinary approach was used, including geomorphological, field‐geology, stratigraphical, morphotectonic, structural, ⁴⁰Ar/³⁹Ar and tephrostratigraphical data. Results indicate that, from the Lower Pleistocene onwards, this sector of the chain was affected by extensional tectonics responsible for the onset of the sedimentation of Quaternary fluvial, alluvial fan and slope deposits. Fault systems are mainly composed of NW‐SE, NE–SW and W‐E trending strike‐slip and normal faults, associated to NW‐SE and NE–SW oriented extensions. Fault scarps, stratigraphical and structural data and morphotectonic indicators suggest that these faults affected the wide piedmont area of the northern Camposauro mountain front in the Lower Pleistocene–Upper Pleistocene time span. Faults affected both the oldest Quaternary slope deposits (Laiano Synthem, Lower Pleistocene) and the overlying alluvial fan system deposits constrained between the late Middle Pleistocene and the Holocene. The latter are geomorphologically and chrono‐stratigraphically grouped into four generations, I generation: late Middle Pleistocene–early Upper Pleistocene, with tephra layers ⁴⁰Ar/³⁹Ar dated to 158±6 and 113±7 ka; II generation: Upper Pleistocene, with tephra layers correlated with the Campanian Ignimbrite (39 ka) and with the slightly older Campi Flegrei activity (⁴⁰Ar/³⁹Ar age 48±7 ka); III generation: late Upper Pleistocene–Lower Holocene, with tephra layers correlated with the Neapolitan Yellow Tuff (~15 ka); IV generation: Holocene in age. The evolution of the first three generations was controlled by Middle Pleistocene extensional tectonics, while Holocene fans do not show evidence of tectonic activity. Nevertheless, considering the moderate to high magnitude historical seismicity of the study area, we cannot rule out that some of the recognized faults may still be active. Copyright © 2018 John Wiley & Sons, Ltd.