Research on karst in the Calabria region recognized three different hypogenic cave systems, all related to sulfidic thermal springs. Cave morphology, the depositional setting and isotopic ...characteristics of gypsum deposits reveal that the main process for cave formation was the oxidation of H2S to sulfuric acid. This process, known as sulfuric acid speleogenesis, was induced by thermal water rising towards the oxidizing zone in tectonic windows where dolomitic or limestone rocks outcrop. The δ34S values of most gypsum deposits prove they originated from sulfuric acid produced by H2S oxidation in the cave atmospheres. Most gypsum deposits in the Calabrian caves, in fact, exhibit δ34S values very similar to those of H2S, not to those of sulfate in the groundwater. On the contrary, the barite and part of the gypsum in the Terme Luigiane have δ34S values similar to those for sulfate in the water, implying that the sulfate minerals precipitated in a subaqueous environment. A large-scale deposition of replacement gypsum occurred only in the water table caves of Cassano, where subaerial corrosion greatly influenced cave morphology and the typical passage cross-sections. In the Terme Luigiane and Mount Sellaro cave systems, these subaerial processes caused only minor changes in inclined passages that had evolved mainly in subaqueous conditions.
•Hypogene cave systems produced by sulfuric acid speleogenesis•Depositional setting and geochemical characteristics of sulfate deposits•Co-existence of subaerial and subaqueous gypsum inside the same cave•Relationship between thermal water hydrodynamic and morphology of the caves
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
We present seismological evidence for the existence of an actively slipping low‐angle normal fault (15° dip) located in the northern Apennines of Italy. During a temporary seismic experiment, we ...recorded ∼2000 earthquakes with ML ≥ 3.1. The microseismicity defines a 500 to 1000 m thick fault zone that crosscuts the upper crust from 4 km down to 16 km depth. The fault coincides with the geometry and location of the Alto Tiberina Fault (ATF) as derived from geological observations and interpretation of depth‐converted seismic reflection profiles. In the ATF hanging wall the seismicity distribution highlights minor synthetic and antithetic normal faults (4–5 km long) that sole into the detachment. The ATF‐related seismicity shows a nearly constant rate of earthquake production, ∼3 events per day (ML ≤ 2.3), and a higher b value (1.06) with respect to the fault hanging wall (0.85) which is characterized by a higher rate of seismicity. In the ATF zone we also observe the presence of clusters of earthquakes occurring with relatively short time delays and rupturing the same fault patch. To explain movements on the ATF, oriented at high angles (∼75°) to the maximum vertical principal stress, we suggest an interpretative model in which crustal extension along the fault is mostly accommodated by aseismic slip in velocity strengthening areas while microearthquakes occur in velocity weakening patches. We propose that these short‐lived frictional instabilities are triggered by fluid overpressures related to the buildup of CO2‐rich fluids as documented by boreholes in the footwall of the ATF.
Alps and Apennines developed along opposite subductions, which inverted the tethyan passive continental margins located along the boundaries of Europe, Africa and the Adriatic plates. The Alps have ...higher morphological and structural elevation, two shallow, slow subsiding foreland basins. The Apennines have rather low morphological and structural elevation, one deep and fast subsiding foreland basin. While the Alps sandwiched the whole crust of both upper and lower plates, the Apennines rather developed by the accretion of the upper crust of the lower plate alone. Alpine relics are boudinated in the hangingwall of the Apennines, stretched by the Tyrrhenian backarc rifting. Relative to the upper plate, the subduction hinge moved toward it in the Alps from Cretaceous to Present, whereas it migrated away in the Apennines from late Eocene to Present, apart in Sicily where since Pleistocene(?) it reversed. The asymmetry appears primarily controlled by the slab polarity with respect to the westward drift of the lithosphere.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
Current studies of fault interaction lack sufficiently long earthquake records and measurements of fault slip rates over multiple seismic cycles to fully investigate the effects of interseismic ...loading and coseismic stress changes on the surrounding fault network. We model elastic interactions between 97 faults from 30 earthquakes since 1349 A.D. in central Italy to investigate the relative importance of co‐seismic stress changes versus interseismic stress accumulation for earthquake occurrence and fault interaction. This region has an exceptionally long, 667 year record of historical earthquakes and detailed constraints on the locations and slip rates of its active normal faults. Of 21 earthquakes since 1654, 20 events occurred on faults where combined coseismic and interseismic loading stresses were positive even though ~20% of all faults are in “stress shadows” at any one time. Furthermore, the Coulomb stress on the faults that experience earthquakes is statistically different from a random sequence of earthquakes in the region. We show how coseismic Coulomb stress changes can alter earthquake interevent times by ~103 years, and fault length controls the intensity of this effect. Static Coulomb stress changes cause greater interevent perturbations on shorter faults in areas characterized by lower strain (or slip) rates. The exceptional duration and number of earthquakes we model enable us to demonstrate the importance of combining long earthquake records with detailed knowledge of fault geometries, slip rates, and kinematics to understand the impact of stress changes in complex networks of active faults.
Key Points
We model elastic stress interactions for 30 earthquakes on 97 faults over 667 years in central Italy
Coseismic Coulomb stresses can cause earthquake interevent time changes for individual faults on the order of 103 years
Coulomb stress changes cause shorter faults to experience more irregular earthquake recurrence intervals and greater slip rate variability
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
We used 1029 earthquakes, with magnitudes ranging from
M
3.0 to
M
6.5, located in central Apennines, Italy, and recorded by 414 local stations to study the variation of the quality factor
Q
S
of ...shear waves with depth. We first determined average nonparametric attenuation functions in the frequency band from 0.5 to 20 Hz and hypocenter distances less than 155 km to correct the observed acceleration spectra for attenuation effects. Then, we separated source and site effects from the corrected spectral records to determine the changes of
Q
S
with depth. We used a 1D local shear-wave velocity model to calculate the travel times of the source-station paths, and we inverted the observed spectra to determine
Q
S
in three different depth intervals (0–4 km, 4–10 km and 10–15 km) and five frequencies (0.5, 1, 4, 10 and 20 Hz). We found that
Q
S
increases with frequency at all depths considered and tends to have lower values at shallow depths. The average value of
Q
S
is consistent with previous studies made in central Italy and can be approximated by
Q
S
= 43
f
0.94
. To describe the frequency dependence of
Q
S
with depth (
H
), we determine the following relations:
Q
S
= 5.5
f
1.39
, 0.5 ≤
f
≤ 10 Hz and
Q
S
= 151.5,
f
> 10 Hz for 0–4 km,
Q
S
= 52
f
0.87
for 4 <
H
< 10 km and
Q
S
= 51
f
0.92
for 10 ≤
H
≤ 15 km. We conclude that the
Q
-depth-dependent model can be useful to improve estimates of source parameters and ground motion prediction in the central Apennines region of Italy.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Several impacts of climate change are becoming evident and will be more and more apparent in the future. The threats and challenges posed by weather patterns variations can change according to the ...variables of interest, geography, and socio-economic contexts. At the moment, we are compelled to assess their impacts, so as to identify priorities and devise effective countermeasures. A major concern is that of geo-hydrological risks, including the potential effects of landslide evolution in unstable areas. Based on available data on the relationship between soil–atmosphere interaction and mobility of a slow active earthflow in Southern Italy, the paper tries to correlate the expected future precipitation potential evapotranspiration balance and the water level fluctuations that govern landslide mobility. The investigation is carried out in the framework of the bottom-up approach known as decision scaling, which lets us evaluate landslide dynamics sensitivity to the variations in soil water budget by means of a simple abacus. Such a tool will make it possible to obtain fast updates on assessing landslide trends when new generations of climate projections become available.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Field observations and petrological and geochemical data are used to constrain a conceptual model for the formation of a gabbro‐peridotite section from Ligurian ophiolites (Italy). The studied ...section is attributed to an intraoceanic domain of the Jurassic Ligurian‐Piedmontese basin and is characterized by the lack of a basalt layer, similar to nonvolcanic segments from (ultra)slow spreading ridges. The proposed model shows a “hot” lithospheric evolution in which melt transport in the mantle under spinel to plagioclase facies conditions occurred mostly in the form of grain‐scale porous flow. We recognize a series of melt/peridotite interaction events, either diffuse or channeled, which modified the composition of the moderately depleted precursor mantle. In particular, localized infiltrations of MORB‐type melts gave rise to formation of spinel websterite layers close to the lithosphere‐asthenosphere boundary. The peridotite‐websterite association was involved in a spinel facies deformation attributed to emplacement of asthenospheric material at the base of the lithosphere. The “hot” lithospheric evolution is followed by an evolution characterized by melt transport through fractures, which started with crystallization of melt into troctolite to olivine gabbro dikes. Both mantle structures and gabbroic dikes are locally crosscut by gabbroic sills. As the mantle section cooled significantly, the dip of the melt migration structures evolved from subvertical to subhorizontal. The growth of a gabbroic pluton (up to ∼400 m thick) that is intruded into the mantle sequence is attributed to accretion of gabbroic sills. The tectonomagmatic history recorded by the gabbroic pluton after its solidification is characterized by ductile shearing developed from near‐solidus to amphibolite facies conditions.
Key Points
Compositional and structural modifications of the mantle section
Melt transport evolution in conjunction with exhumation
Similarities between studied ophiolite and modern (ultra)slow spreading ridges
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Among the many GIS based multivariate statistical methods for landslide susceptibility zonation, the so called “Conditional Analysis method” holds a special place for its conceptual simplicity. In ...fact, in this method landslide susceptibility is simply expressed as landslide density in correspondence with different combinations of instability-factor classes. To overcome the operational complexity connected to the long, tedious and error prone sequence of commands required by the procedure, a shell script mainly based on the GRASS GIS was created. The script, starting from a landslide inventory map and a number of factor maps, automatically carries out the whole procedure resulting in the construction of a map with five landslide susceptibility classes. A validation procedure allows to assess the reliability of the resulting model, while the simple mean deviation of the density values in the factor class combinations, helps to evaluate the goodness of landslide density distribution. The procedure was applied to a relatively small basin (167 km²) in the Italian Northern Apennines considering three landslide types, namely rotational slides, flows and complex landslides, for a total of 1,137 landslides, and five factors, namely lithology, slope angle and aspect, elevation and slope/bedding relations. The analysis of the resulting 31 different models obtained combining the five factors, confirms the role of lithology, slope angle and slope/bedding relations in influencing slope stability.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The lithological content and mineralogical assemblage of main tephra layers (V1, V2, V3, V4, V5, V7) embedded in the Montalbano Jonico succession have been fully characterized. Major-element analyses ...were carried out on the juvenile glass fractions and main crystal phases, and trace-element contents were determined on glasses extracted from the thickest layer of the sequence (V5). Single crystal 40Ar/39Ar laser fusions were performed on sanidine from the V4 layer, yielding a weighted mean age of 773.9 ± 1.3 ka. The Vulture volcano is likely the source of two tephra layers, V3 and V4, embedded to the middle part of the Interval B of the sequence, which represent the oldest products of this center ever found. Moreover, the V4 layer was emplaced near the Matuyama–Bruhnes Chron boundary, and thus serves as an important chronostratigraphic marker. Complete chemical characterization of V5 allows us to suggest the Campanian Volcanic Zone as its eruptive source; corroborating the idea that activity there began at ∼720 ka and spanned most of the Middle Pleistocene. Finally, we insert our new framework from the Montalbano Jonico sequence into a reappraised tephra sequence from the Middle Pleistocene to present in southern Italy, which results in a more robust series of tephrostratotypes and improves the reliability of inter-archive correlations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
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