Thèses sur le sujet « Southernl Apennines »

The stratigraphy and sedimentology of Mesozoic carbonate platform-margins cropping out in southern Italy are investigated. New strati graphic data are presented from northern and eastern slopes of the Apennine carbonate platform, based on locallycorrelated field sections. Thin-section petrography is used to demonstrate the spatial and temporal distribution of derived lithoclasts. Results indicate that southern Apennine platforms underwent repeated erosion during Cretaceous time and possible reasons for this are discussed. Petrographic studies also provided outline sediment parageneses for slopes and platforms, with special reference to the detailed geochemistry of secondary dolomite formation on the eastern margin of the Apulian platform, whose growth is indicated by proton microprobe microanalysis to have been influenced by redox changes. The sedimentary facies and sediment geometries of Upper Cretaceous to Lower Tertiary slope sediments mapped in the Frosolone area are discussed in a case-study. Cross-sections showing geometries of key beds are presented, and depositional controls are discussed. Outcrop data suggest an Early to Middle Jurassic age of basin formation of this sector of the Lagonegro-Molise basin. A further case study from the Mesozoic slope in the Gran Sasso shows sediment geometries at reflection seismic scale, and relates them to possible depositional control by relative sea-level fluctuations. Finally, data from southern Apennine platforms and basins are combined in a tentative sequence stratigraphic framework for the Middle Cretaceous. The results of onedimensional subsidence modelling are presented in order to separate and describe the signals of local tectonics and relative sea-level fluctuations affecting the southern passive-margin of Mesozoic Tethys.

In the last years, geodetic measurements have shown that temporal variations in total groundwater content induce transient deformations of the crust that are mostly reflected in the vertical component. Here we present new GPS observations showing a noticeable non-tectonic transient deformation in the Apennines (Italy), mostly evident in the horizontal components, that correlate with multi-annual hydrological signals as measured by rainfall, GRACE (Gravity Recovery and Climate Experiment) and discharge of karst springs. The observed transient signal is superimposed on the long-term ~3mm/yr NE-SW directed active extension, correlates with the seasonal recharge/discharge cycle of groundwater flow and its multi-annual variations and appears to modulate the intensity of tectonic extensional opening in those regions characterized by large carbonate aquifers. In particular, periods of increasing discharge from karstic spring correlate with an enhanced extensional signal, whereas exhaustion periods correlate with reduced extensional signal. Vertical observations, being correlated with GRACE data, reflect the hydrological load variation over regional (European) scale. Horizontal deformations, conversely, affect mostly the sites located near the large carbonate massifs of the Apennines and can't be explained as load induced response. We suggest that the horizontal observed deformation is related to the presence of highly fractured shallow crust that deforms according to variable conditions of the hydraulic head within the large carbonate aquifers. We therefore propose two different models that simulates the effect of a medium permeated with sub-vertical opening fractures. These new findings could contribute to the understanding of the deformation of the large carbonate aquifers and to an improved management of these important natural resources. By focusing on the 2009 L'Aquila earthquake, we finally highlight the difficulties that arise for the estimation of interseimic trends and small tectonic signals in areas affected by such significant non-tectonic deformations.

In the last years, geodetic measurements have shown that temporal variations in total groundwater content induce transient deformations of the crust that are mostly reflected in the vertical component. Here we present new GPS observations showing a noticeable non-tectonic transient deformation in the Apennines (Italy), mostly evident in the horizontal components, that correlate with multi-annual hydrological signals as measured by rainfall, GRACE (Gravity Recovery and Climate Experiment) and discharge of karst springs. The observed transient signal is superimposed on the long-term ~3mm/yr NE-SW directed active extension, correlates with the seasonal recharge/discharge cycle of groundwater flow and its multi-annual variations and appears to modulate the intensity of tectonic extensional opening in those regions characterized by large carbonate aquifers. In particular, periods of increasing discharge from karstic spring correlate with an enhanced extensional signal, whereas exhaustion periods correlate with reduced extensional signal. Vertical observations, being correlated with GRACE data, reflect the hydrological load variation over regional (European) scale. Horizontal deformations, conversely, affect mostly the sites located near the large carbonate massifs of the Apennines and can't be explained as load induced response. We suggest that the horizontal observed deformation is related to the presence of highly fractured shallow crust that deforms according to variable conditions of the hydraulic head within the large carbonate aquifers. We therefore propose two different models that simulates the effect of a medium permeated with sub-vertical opening fractures. These new findings could contribute to the understanding of the deformation of the large carbonate aquifers and to an improved management of these important natural resources. By focusing on the 2009 L'Aquila earthquake, we finally highlight the difficulties that arise for the estimation of interseimic trends and small tectonic signals in areas affected by such significant non-tectonic deformations.

In this research work I analyzed the instrumental seismicity of Southern Italy in the area including the Lucanian Apennines and Bradano foredeep, making use of the most recent seismological database available so far. I examined the seismicity occurred during the period between 2001 and 2006, considering 514 events with magnitudes M ≥ 2.0. In the first part of the work, P- and S-wave arrival times, recorded by the Italian National Seismic Network (RSNC) operated by the Istituto Nazionale di Geofisica e Vulcanologia (INGV), were re-picked along with those of the SAPTEX temporary array (2001–2004). For some events located in the Upper Val d'Agri, I also used data from the Eni-Agip oil company seismic network. I computed the VP/VS ratio obtaining a value of 1.83 and I carried out an analysis for the one-dimensional (1D) velocity model that approximates the seismic structure of the study area. After this preliminary analysis, making use of the records obtained in the SeSCAL experiment, I incremented the database by handpicking new arrival times. My final dataset consists of 15,666 P- and 9228 S-arrival times associated to 1047 earthquakes with magnitude ML ≥ 1.5. I computed 162 fault-plane solutions and composite focal mechanisms for closely located events. I investigated stress field orientation inverting focal mechanism belonging to the Lucanian Apennine and the Pollino Range, both areas characterized by more concentrated background seismicity. Moreover, I applied the double difference technique (DD) to improve the earthquake locations. Considering these results and different datasets available in the literature, I carried out a detailed analysis of single sub-areas and of a swarm (November 2008) recorded by SeSCAL array. The relocated seismicity appears more concentrated within the upper crust and it is mostly clustered along the Lucanian Apennine chain. In particular, two well-defined clusters were located in the Potentino and in the Abriola-Pietrapertosa sector (central Lucanian region). Their hypocentral depths are slightly deeper than those observed beneath the chain. I suggest that these two seismic features are representative of the transition from the inner portion of the chain with NE-SW extension to the external margin characterized by dextral strike-slip kinematics. In the easternmost part of the study area, below the Bradano foredeep and the Apulia foreland, the seismicity is generally deeper and more scattered and is associated to the Murge uplift and to the small structures present in the area. I also observed a small structure NE-SW oriented in the Abriola-Pietrapertosa area (activated with a swarm in November 2008) that could be considered to act as a barrier to the propagation of a potential rupture of an active NW-SE striking faults system. Focal mechanisms computed in this study are in large part normal and strike-slip solutions and their tensional axes (T-axes) have a generalized NE-SW orientation. Thanks to denser coverage of seismic stations and the detailed analysis, this study is a further contribution to the comprehension of the seismogenesis and state of stress of the Southern Apennines region, giving important contributions to seismotectonic zoning and seismic hazard assessment.

In this research work I analyzed the instrumental seismicity of Southern Italy in the area including the Lucanian Apennines and Bradano foredeep, making use of the most recent seismological database available so far. I examined the seismicity occurred during the period between 2001 and 2006, considering 514 events with magnitudes M ≥ 2.0. In the first part of the work, P- and S-wave arrival times, recorded by the Italian National Seismic Network (RSNC) operated by the Istituto Nazionale di Geofisica e Vulcanologia (INGV), were re-picked along with those of the SAPTEX temporary array (2001–2004). For some events located in the Upper Val d'Agri, I also used data from the Eni-Agip oil company seismic network. I computed the VP/VS ratio obtaining a value of 1.83 and I carried out an analysis for the one-dimensional (1D) velocity model that approximates the seismic structure of the study area. After this preliminary analysis, making use of the records obtained in the SeSCAL experiment, I incremented the database by handpicking new arrival times. My final dataset consists of 15,666 P- and 9228 S-arrival times associated to 1047 earthquakes with magnitude ML ≥ 1.5. I computed 162 fault-plane solutions and composite focal mechanisms for closely located events. I investigated stress field orientation inverting focal mechanism belonging to the Lucanian Apennine and the Pollino Range, both areas characterized by more concentrated background seismicity. Moreover, I applied the double difference technique (DD) to improve the earthquake locations. Considering these results and different datasets available in the literature, I carried out a detailed analysis of single sub-areas and of a swarm (November 2008) recorded by SeSCAL array. The relocated seismicity appears more concentrated within the upper crust and it is mostly clustered along the Lucanian Apennine chain. In particular, two well-defined clusters were located in the Potentino and in the Abriola-Pietrapertosa sector (central Lucanian region). Their hypocentral depths are slightly deeper than those observed beneath the chain. I suggest that these two seismic features are representative of the transition from the inner portion of the chain with NE-SW extension to the external margin characterized by dextral strike-slip kinematics. In the easternmost part of the study area, below the Bradano foredeep and the Apulia foreland, the seismicity is generally deeper and more scattered and is associated to the Murge uplift and to the small structures present in the area. I also observed a small structure NE-SW oriented in the Abriola-Pietrapertosa area (activated with a swarm in November 2008) that could be considered to act as a barrier to the propagation of a potential rupture of an active NW-SE striking faults system. Focal mechanisms computed in this study are in large part normal and strike-slip solutions and their tensional axes (T-axes) have a generalized NE-SW orientation. Thanks to denser coverage of seismic stations and the detailed analysis, this study is a further contribution to the comprehension of the seismogenesis and state of stress of the Southern Apennines region, giving important contributions to seismotectonic zoning and seismic hazard assessment.

The southern Apennines of Italy have been experienced several destructive earthquakes both in historic and recent times. The present day seismicity, characterized by small-to-moderate magnitude earthquakes, was used like a probe to obatin a deeper knowledge of the fault structures where the largest earthquakes occurred in the past. With the aim to infer a three dimensional seismic image both the problem of data quality and the selection of a reliable and robust tomographic inversion strategy have been faced. The data quality has been obtained to develop optimized procedures for the measurements of P- and S-wave arrival times, through the use of polarization filtering and to the application of a refined re-picking technique based on cross-correlation of waveforms. A technique of iterative tomographic inversion, linearized, damped combined with a strategy of multiscale inversion type has been adopted. The retrieved P-wave velocity model indicates the presence of a strong velocity variation along a direction orthogonal to the Apenninic chain. This variation defines two domains which are characterized by a relatively low and high velocity values. From the comparison between the inferred P-wave velocity model with a portion of a structural section available in literature, the high velocity body was correlated with the Apulia carbonatic platforms whereas the low velocity bodies was associated to the basinal deposits. The deduced Vp/Vs ratio shows that the ratio is lower than 1.8 in the shallower part of the model, while for depths ranging between 5 km and 12 km the ratio increases up to 2.1 in correspondence to the area of higher seismicity. This confirms that areas characterized by higher values are more prone to generate earthquakes as a response to the presence of fluids and higher pore-pressures.

The southern Apennines of Italy have been experienced several destructive earthquakes both in historic and recent times. The present day seismicity, characterized by small-to-moderate magnitude earthquakes, was used like a probe to obatin a deeper knowledge of the fault structures where the largest earthquakes occurred in the past. With the aim to infer a three dimensional seismic image both the problem of data quality and the selection of a reliable and robust tomographic inversion strategy have been faced. The data quality has been obtained to develop optimized procedures for the measurements of P- and S-wave arrival times, through the use of polarization filtering and to the application of a refined re-picking technique based on cross-correlation of waveforms. A technique of iterative tomographic inversion, linearized, damped combined with a strategy of multiscale inversion type has been adopted. The retrieved P-wave velocity model indicates the presence of a strong velocity variation along a direction orthogonal to the Apenninic chain. This variation defines two domains which are characterized by a relatively low and high velocity values. From the comparison between the inferred P-wave velocity model with a portion of a structural section available in literature, the high velocity body was correlated with the Apulia carbonatic platforms whereas the low velocity bodies was associated to the basinal deposits. The deduced Vp/Vs ratio shows that the ratio is lower than 1.8 in the shallower part of the model, while for depths ranging between 5 km and 12 km the ratio increases up to 2.1 in correspondence to the area of higher seismicity. This confirms that areas characterized by higher values are more prone to generate earthquakes as a response to the presence of fluids and higher pore-pressures.

The aim of this work was to show that refined analyses of background, low magnitude seismicity allow to delineate the main active faults and to accurately estimate the directions of the regional tectonic stress that characterize the Southern Apennines (Italy), a structurally complex area with high seismic potential. Thanks the presence in the area of an integrated dense and wide dynamic network, was possible to analyzed an high quality microearthquake data-set consisting of 1312 events that occurred from August 2005 to April 2011 by integrating the data recorded at 42 seismic stations of various networks. The refined seismicity location and focal mechanisms well delineate a system of NW-SE striking normal faults along the Apenninic chain and an approximately E-W oriented, strike-slip fault, transversely cutting the belt. The seismicity along the chain does not occur on a single fault but in a volume, delimited by the faults activated during the 1980 Irpinia M 6.9 earthquake, on sub-parallel predominant normal faults. Results show that the recent low magnitude earthquakes belongs to the background seismicity and they are likely generated along the major fault segments activated during the most recent earthquakes, suggesting that they are still active today thirty years after the mainshock occurrences. In this sense, this study gives a new perspective to the application of the high quality records of low magnitude background seismicity for the identification and characterization of active fault systems. The analysis of the stress tensor inversion provides two equivalent models to explain the microearthquake generation along both the NW-SE striking normal faults and the E- W oriented fault with a dominant dextral strike-slip motion, but having different geological interpretations. We suggest that the NW-SE-striking Africa-Eurasia convergence acts in the background of all these structures, playing a primary and unifying role in the seismotectonics of the whole region.

The aim of this work was to show that refined analyses of background, low magnitude seismicity allow to delineate the main active faults and to accurately estimate the directions of the regional tectonic stress that characterize the Southern Apennines (Italy), a structurally complex area with high seismic potential. Thanks the presence in the area of an integrated dense and wide dynamic network, was possible to analyzed an high quality microearthquake data-set consisting of 1312 events that occurred from August 2005 to April 2011 by integrating the data recorded at 42 seismic stations of various networks. The refined seismicity location and focal mechanisms well delineate a system of NW-SE striking normal faults along the Apenninic chain and an approximately E-W oriented, strike-slip fault, transversely cutting the belt. The seismicity along the chain does not occur on a single fault but in a volume, delimited by the faults activated during the 1980 Irpinia M 6.9 earthquake, on sub-parallel predominant normal faults. Results show that the recent low magnitude earthquakes belongs to the background seismicity and they are likely generated along the major fault segments activated during the most recent earthquakes, suggesting that they are still active today thirty years after the mainshock occurrences. In this sense, this study gives a new perspective to the application of the high quality records of low magnitude background seismicity for the identification and characterization of active fault systems. The analysis of the stress tensor inversion provides two equivalent models to explain the microearthquake generation along both the NW-SE striking normal faults and the E- W oriented fault with a dominant dextral strike-slip motion, but having different geological interpretations. We suggest that the NW-SE-striking Africa-Eurasia convergence acts in the background of all these structures, playing a primary and unifying role in the seismotectonics of the whole region.

An "active and capable fault" (ACF) defines an active fault able to permanently dislocate the ground surface, while a "seismogenic source" (SS) is a fault capable of generating earthquakes. When the deep coseismic rupture along a SS propagates towards the surface, the latter can be permanently dislocated. Consequently, the geological features of an ACF could be considered the surface expression of the deep activity of a SS. For example, the geological studies, carried out before the seismic sequences of central Italy along the faults responsible for the main earthquakes of 2009 and 2016-2017, are been partly confirmed by the coseismic ruptures produced during these seismic sequences. This highlighted the importance of defining in a "preventive" way what are the ACFs and SSs and where they are located in a given area. The dichotomy between ACF and SS in Italy is, however, still marked in the literature, resulting in the presence of two national databases: the "Catalog of capable faults" (ITHACA) and the "Database of Individual Seismogenic Sources" (DISS) which deal with ACF and SS, respectively. Nonetheless, the analysis of the two databases highlights the presence of some conceptual and critical differences that can not permit conceptual and factual interoperability between them. These difficulties highlight the lack of criteria used for the assessment of the ACF and SS and, therefore, the need to define a clear and well-defined methodological approach, allowing to map an ACF in relation to a SS. The following Ph.D. research, therefore, proposes a conceptual model able to combine the concept of ACF with that of an SS. The result of this model is represented by a prototype thematic map (Attached I) of ACFs that represent the superficial expression of SSs, in the central-southern Apennines. The realization of the conceptual model and the identification of the geological and segmentation criteria, useful for establishing the relationship between ACF and SS (the object of Map C), were made possible by the use of a multidisciplinary methodological approach: the acquisition and analysis of literature, photogeological analysis and, especially, the acquisition of geological, geomorphological, structural and paleoseismological data in 5 test areas of the central-southern Apennines. These geological studies have allowed clarifying that many of the criteria, used individually to assess an ACF as an expression of a SS, may not always be sufficient to define the presence of ACF in a given area if they are not framed within a comprehensive geological study. The use of this approach and the resulting map (Attached I) provides the knowledge to conceptually relate the main ACFs of the central-southern Apennines with the respective SSs, superimposing seismogenic parameters to information concerning the distribution and entity of permanent dislocations of the ground surface. These elements represent the input data for an evaluation of the seismic hazard of a given area, in terms both of maximum magnitude expectations, useful for the definition of shaking scenarios in the context of the design of infrastructures and major buildings, and surface faulting hazard for land planning studies.

La mugheta del Parco Nazionale della Majella è una formazione isolata e relittuale, testimonianza vivente della possibile serie vegetazionale climacica della fascia subalpina in Appennino centrale. Il pino mugo cresce solitamente sopra il limite altitudinale degli alberi (timberline) e trova nel massiccio della Majella il limite meridionale del suo areale di distribuzione. Questa vegetazione ecotonale, di transizione tra il bosco denso di faggio e le praterie alpine, sensibile anche alle minime variazioni ambientali, rappresenta un ottimo indicatore degli effetti dei recenti cambiamenti climatici e di uso del suolo in atto nel Bacino del Mediterraneo. Le tendenze climatiche previste per quest’area includono un aumento delle temperature ed una diversa stagionalità delle precipitazioni, con aumento nei mesi invernali e diminuzione nei mesi estivi e autunnali. In Appennino, inoltre, la vegetazione arbustiva del piano subalpino è stata drasticamente ridotta in passato dall’azione diretta dell’uomo, per far spazio al pascolo d’alta quota. L’attuale e progressivo abbandono dei pascoli d’alta quota, però, sta permettendo una ricolonizzazione del piano alpino con la libera evoluzione delle serie vegetazionali. Questo lavoro ha l’obiettivo di valutare, mediante tre diversi approcci metodologici, gli effetti delle variazioni d'uso del suolo e dei cambiamenti climatici sulle dinamiche evolutive dei popolamenti di pino mugo nel massiccio della Majella. Un confronto diacronico svolto a scala di paesaggio, su fotogrammi aerei opportunamente ortorettificati e ortofoto digitali, ha mostrato una progressiva espansione della mugheta. Il contributo di indagini condotte in archivi di Stato e sedi ISTAT ha dimostrato una concomitante drastica riduzione della pratica del pascolo. Il ruolo delle variabili climatiche nella crescita del pino mugo è stato indagato mediante analisi dendroclimatologiche su carote legnose di pino mugo. Le relazioni clima-accrescimento sono state definite mediante funzioni di correlazione (CF), la cui variabilità nel tempo in risposta ai cambiamenti climatici è stata valutata con funzioni di correlazione a finestra mobile (MCF). I risultati hanno dimostrato che le variabili climatiche influenzano la crescita del pino mugo nell’ecotono della treeline sul massiccio della Majella. Significative CF sono state ottenute con le temperature massime primaverili e le precipitazioni estive. Le MCF hanno dimostrato che il pino mugo è una specie sensibile alle variazioni climatiche , in termini di crescita radiale, in particolare all'inizio e alla fine della stagione vegetativa. Il significato delle correlazioni ottenute è stato indagato con analisi anatomiche svolte a livello di singolo individuo che hanno permesso di definire le tempistiche della xilogenesi nel pino mugo. Le diverse fasi fenologiche (divisione e crescita cellulare, ispessimento della parete secondaria e completa lignificazione delle tracheidi) sono state monitorate durante un’intera stagione vegetativa, indagando contemporaneamente sulle tempistiche di formazione del legno di compressione (CW) e sulle differenze con il legno opposto (OW). Un maggior numero di cellule con parete secondaria più spessa è stato osservato nel CW, con tempi di formazione più lunghi rispetto al OW. Maggio rappresenta l’inizio della stagione vegetativa del pino mugo sul massiccio della Majella, settembre e ottobre la fine. Un incremento delle temperature primaverili permetterebbe un’anticipazione della riattivazione vegetativa e di conseguenza un allungamento della stagione di crescita del pino mugo. È quindi possibile confermare un’evoluzione della mugheta dovuta soprattutto all’abbandono dei pascoli, ma anche influenzata dagli andamenti climatici. Una eccessiva espansione della mugheta, principalmente verso quote maggiori, rappresenterebbe una minaccia per le specie rare ed endemiche presenti nei pascoli alpini del Parco Nazionale della Majella. Tuttavia, politiche di conservazione e salvaguardia dovranno allo stesso tempo evitare una eccessiva riduzione della mugheta e quindi la scomparsa dell’ultimo nucleo presente in Appennino.
Mountain pine krummholz within the Majella National Park forms an isolated patch and is a relictual species, thought representing the potential natural vegetation of the subalpine belt in Central Apennines, Italy. Mountain pine grows above the timberline and has in the Majella massif its southernmost limit of the distributional range. This vegetation dominates the treeline ecotone, between the dense beech forest and the alpine prairies, and is highly sensitive even to minor environmental changes. For this reason, it is a major proxy for monitoring the effects of climate and land-use changes occurring in the Mediterranean Basin. Mediterranean climatic trend includes projected increasing temperature and a different distribution of total precipitation, which are increasing during winter and decreasing during summer and autumn, respectively. Moreover, in Central Apennines, subalpine shrublands have been deeply reduced from the past anthropic practices. The recent abandonment of marginal areas and grazing cessation are allowing a re-colonization of areas previously grazed. The main objective of this study was to assess the effects of land-use and climatic changes on mountain pine population dynamics in the Majella massif, using three different methodological approaches. Temporal and spatial distribution of mountain pine since 1954 was reconstructed and a multitemporal map was created by historical aerial ortophotos. Results documented an upward and downward expansion of mountain pine and an ingrowth into the formerly tree-free grassland in early 1900s, together with a decline of the local human population and livestock. The relative role of climatic variables on mountain pine growth was assessed by dendroclimatological analysis. Climate-growth relationship were assessed by correlation function (CF) analysis and moving CF (MCF), investigating the possible deviations in the response of mountain pine to recent climate change. Results demonstrated that climate variables affected mountain pine growth at the treeline ecotone in the Majella massif. Significant correlations were found with the spring maximum temperatures and summer precipitation. MCF showed that mountain pine is a sensitive species, in terms of tree ring growth, particularly at the beginning and at the end of the growing season. For better understand dendroclimatological results, wood anatomical analyses were conducted. Timings of mountain pine xylogenesis were assessed and the principal phenological phases (cambial division; enlargement; wall thickening; mature) were monitored during the entire growing season. At the same time timings of compression wood (CW) formation and possible differences with the opposite wood (OW) formation were investigated. Results indicated that CW is characterized by higher number of cells and thicker secondary wall, as well as longer xylogenesis compared with the OW. The growing season started simultaneously in both types of wood (on 20 May), and ended two week earlier in OW (on 22 September) than in CW (on 6 October). Increasing temperature of spring month would be favourable for the elongation of mountain pine growing season, which would probably start early, though decreasing precipitation could compromise wood formation during summer, mountain pine being highly sensitive to this climatic parameter. Growing above the limit of tree vegetation, mountain pine proved to be a promising species for monitoring climate- and land use-driven influences over tree-ring growth at high elevation. An excessive expansion of mountain pine krummholz, mainly at higher altitudes, may represent a threat for rare and endemic species growing in the alpine grasslands of the Majella National Park. However, conservation and preservation of mountain pine are required, in order to avoid a severe reduction of its distribution and then the risk of extinction of the last “island” present in the Apennine.

Lo studio effettuato in questa tesi di Dottorato ha lo scopo di integrare metodologie di analisi diverse - geologiche, geofisiche e statistiche - per contribuire alla determinazione del potenziale sismico, che è la diretta espressione dell’attività del campo di stress attualmente agente e responsabile della sismicità. Queste tre diverse metodologie sono state applicate in due aree selezionate ubicate lungo la catena appenninica, in corrispondenza delle conche intramontane di origine tettonica. La scelta di queste aree si basa anche sul presupposto che esse possano avere un notevole potenziale sismico essendo caratterizzate da importanti eventi storici di elevata magnitudo. Tra le metodologie applicate in questo studio, i metodi geologici mirano alla comprensione dell’evoluzione quaternaria delle depressioni intrappenniniche con particolare riguardo al riconoscimento ed alla valutazione delle evidenze di tettonica attiva. I metodi geofisici sono stati applicati per studiare e definire meglio il campo di stress attraverso l’analisi dei dati di borehole breakout, dei meccanismi focali dei terremoti e del test di Leak-off. Tutte le tecniche sono volte a determinare le componenti relative al campo di stress quali orientazione (Shmin ed asse-T), tipo di regime (normale, trascorrente o inverso) e sua quantificazione (pressioni in MPa). È stato inizialmente affrontato uno studio della sismicità storica e strumentale, attraverso l’analisi dei vari cataloghi, per integrare le conoscenze sulla geodinamica dell’Appennino, sull’assetto geologico-strutturale profondo, sulla definizione delle strutture sismogeniche, sulla distribuzione e sul potenziale sismico delle aree campioni. È stata affrontata l’analisi delle sequenze sismiche per determinare la distribuzione areale ed in profondità degli eventi, l’orientazione ed il tipo di regime di stress e la stima del tensore dello stress regionale mediante il metodo di inversione di GEPHART & FORSYTH (1984). Infine, sono stati applicati due metodi statistici per studiare la distribuzione spazio-temporale dei terremoti tramite due approcci non-parametrici: l’analisi multivariata che implementa il dato di sismicità con quello geologico-strutturale (FAENZA et al., 2003) ed il metodo di TANNER & WONG, 1984) che utilizza solo i dati di sismicità relativi ad un campione omogeneo. Infine, è stata calcolata la probabilità di evento nelle due aree campioni.
Universitá di Bologna "Alma Mater Studiorum" e INGV
Unpublished
3.2. Tettonica attiva
open

Ocean-continent convergence and subsequent continental collision are responsible for continental growth, mountain building, and severe tectonic events including volcanic eruptions and earthquake activity. They are also key driving forces behind the extensive thermal and compositional heterogeneities at crustal and mantle depths. Active subduction along the Calabrian Arc in southern Italy and the Hellenic Arc are examples of such collisional tectonics. The first part of this thesis examines the subduction related deformations within the crust beneath the southern Apennines. By modeling regional surface wave recordings of the largest temporary deployment in the southern Apennines, a lower-crustal/upper-mantle low-velocity volume extending down to 50 km beneath the mountain chain is identified. The magnitude (~ 0.4 km/s slower) and anisotropic nature (~ 10%) of the anomaly suggest the presence of hot and partially molten emplacement that may extend into the upper-crust towards Mt. Vulture, a once active volcano. Since the Apulian basement units are deformed during the compressional and consequent extensional events, our observations favor the ``thick-skin'' tectonic growth model for the region. In the deeper mantle, active processes are thermodynamically imprinted on the depth and strength of the phase transitions. This thesis examines more than 15000 SS precursors and provides the present-day reflectivity structure and topography associated with these phase transitions. Through case studies I present ample evidence for both slab penetration into the lower mantle (beneath the Hellenic Arc, Kurile Island and South America) and slab stagnation at the bottom of the Mantle Transition Zone (beneath the Tyrrhenian Sea and eastern China). Key findings include (1) thermal anomalies (~ 200 K) at the base of the MTZ, which represent the deep source for Cenozoic European Rift Zone, Mount Etna and Mount Cameroon volcanism, (2) significant depressions (by 20-40 km) at the bottom of the Mantle Transition Zone beneath subducting slabs, (3) a strong 520-km reflector near subducting slabs, (4) a weak and elevated (15-25 km) 410-km reflector within active deformation zones, (5) strong lower mantle reflectors (~ 900 km) while slabs penetrate into the lower mantle, and (6) consistency between the topography of a 300-km reflector and an exothermic phase transformation.
Geophysics

Un progetto di cartografia geologica di dettaglio (scala 1:10.000) ha coinvolto circa 135 kmq della Dorsale Narnese-Amerina (Appennino centrale). Il lavoro di terreno è stato svolto avvalendosi delle metodologie tradizionali del rilevamento geologico, alle quali però è stato associato il riconoscimento di particolari caratteri stratigrafico-sedimentologici tali da permettere la definizione di peculiari contesti deposizionali mesozoici tipici dell'Appennino Umbro-Marchigiano-Sabino. La carta geologica e la ri-definizione della litostratigrafia dell'area analizzata sono stati i primi prodotti del progetto. A questi è susseguita la ricostruzione della paleogeografia mesozoica della Dorsale Narnese-Amerina. Sono stati riconosciuti numerosi elementi morfostrutturali ereditati dal rifting del Giurassico Inferiore. Questa fase estensionale smembrò l'estesa paleo-piattaforma del Calcare Massiccio e, per quanto riguarda il Dominio Umbro-Marchigiano-Sabino, causò l'annegamento della fabbrica bentonica e provocò un tipico assetto ad alti e bassi strutturali intrabacinali. Numerosi blocchi di footwall delle faglie giurassiche caratterizzano il settore in analisi, e il riconoscimento è stato possibile mediante l'analisi delle paleoscarpate sottomarine in quanto le tipiche successioni condensate di alto strutturale non affiorano per erosione o per tettonica. Una particolarità è rappresentata da blocchi di Calcare Massiccio (diametro > 100 m) inglobati in successioni bacinali, che hanno portato alla deposizione di facies ad affinità condensata in un contesto deposizionale puramente bacinale. Sono state riconosciute torbiditi carbonatiche con materiale bentonico intercalate in pelagiti di età post-Pliensbachiano del settore Amerino, permettendo di porre dei vincoli sulla ricostruzione paleogeografica dell'Appennino centrale e sulla definizione delle influenze esercitate dagli elementi morfostrutturali sulla deposizione di materiale neritico esportato dalla Piattaforma Carbonatica Laziale-Abruzzese. Durante il Cretaceo Inferiore alcune discontinuità giurassiche sono state ri-utilizzate da una neo-identificata tettonica estensionale post-rift. Le maggiori evidenze dell'attività delle faglie dirette cretacee sono: i) contatti stratigrafici inconformi tra il Calcare Massiccio e depositi del Cretaceo inferiore sommitale (Marne a Fucoidi) a causa del ringiovanimento di margini giurassici; ii) la deposizione di brecce sin-tettoniche intercalate nelle pelagiti cretacee e poggianti in discordanza su scarpate di faglia sottomarine; iii) slumps, nicchie di distacco e faglie sin-sedimentarie che caratterizzano il top della Maiolica. E' stato operato anche un confronto tra l'Appennino Umbro-Sabino e il Sud-Alpino per definire l'influenza delle strutture giurassiche sullo sviluppo delle faglie dirette cretacee. Con il coinvolgimento del settore Narnese-Amerino nelle deformazioni compressive mioceniche ed estensionali post-orogeniche (Pliocene), è stato possibile riconoscere come le discontinuità ereditate dal Mesozoico abbiano controllato la propagazione delle faglie cenozoiche. In particolare, i sovrascorrimenti e le rampe laterali/faglie di strappo legati alla strutturazione dell'Appennino tagliarono i margini giurassici e cretacei senza riattivazione dei piani ereditati. Il rapporto tra paleogeografia mesozoica e orogenesi non poteva escludere gli olistoliti di Calcare Massiccio, argomento questo del tutto nuovo. A causa della differente reologia tra i blocchi di calcari peritidali e le pelagiti nelle quali sono inglobati, sono stati riconosciuti contatti tettonici su originari contatti stratigrafici in quanto gli olistoliti non sono stati in grado di descrivere pieghe della stessa lunghezza d'onda delle unità bacinali pelagiche. Infine le faglie dirette plioceniche non riutilizzarono le superfici di discontinuità mesozoiche in quanto ruotate dai sovrascorrimenti, ma ne sfruttarono solo lo strike.
A detailed geological mapping project (scale 1:10.000) of about 135 kmq involved the Narni-Amelia Ridge (Central Apennines). During the field-work were used the traditional methodologies of the field mapping associated with the identification of characteristic stratigraphic-sedimentological features that allow to define peculiar Mesozoic depositional settings. The first products of the project were the 1:10.000 scale geological map and the re-definition of the lithostratigraphy of the study area. About the paleogeography, several morphostructural elements inherited by the Early Jurassic rifting stage were recognized. This extensional stage dismembered the vast Calcare Massiccio paleo-platform, and the drowning of the benthic factories led to the development of two main sedimentary environments: pelagic carbonate platforms (PCPs) and basins. The Early Jurassic rift architecture is documented by facies and thickness variations of the Jurassic-Lower Cretaceous post-rift succession. Several footwall-blocks of the Jurassic normal faults characterize the Narni-Amelia Ridge. Although the PCP-top successions are not exposed due to post-Jurassic faulting and modern erosion, highly distinctive facies associations define the escarpment margins of these platforms and the adjacent hangingwall-block successions that onlap them, which often embed gravity-driven deposits including rock-fall megaclastics. Fine-grained calcarenites made of shallow water-derived material were found embedded in post-Pliensbachian deposits of the basin-fill succession in the Amelia area. This occurrence is unexpected as these deposits postdate the drowning of the local Calcare Massiccio carbonate platform, which suggests provenance from the Latium-Abruzzi Platform. This provides new evidence for restoring the Jurassic paleogeography of Central Apennines, and for deciphering the itineraries of resedimented carbonate sands from this relatively distant source-area. A newly-identified, post-rift, extensional tectonic affected the Early Jurassic inherited structures during the Early Cretaceous. Evidence for this extensional tectonic phaseare: i) the unconformable contact between the Marne a Fucoidi Fm. (Aptian-Albian) and the Hettangian shallow-water carbonates of the Calcare Massiccio Fm., as a result of rejuvenation and erosion of the Early Jurassic margin of the Amelia intra-basinal high; ii) the occurrence of syn-tectonic breccias embedded in Cretaceous pelagites and locally resting on the submarine fault escarpments; iii) the presence of slumps, scars and syn-sedimentary faults at the top of the Maiolica Fm (Tithonian-early Aptian). Due to the stratigraphic, sedimentological and paleotectonic similarities with the Southern Alps, the two sectors (Narni-Amelia Ridge vs. Ballino area) were compared. The aim of this work was to understand the influence on inherited Jurassic structures on the development of Early Cretaceous extensional faults in two different paleogeographic domains of Italy, albeit with a comparable tectono-sedimentary evolution. During the involvment in Miocene orogenic deformations of the Narni-Amelia Chain, the Jurassic structural highs became part of the hangingwall-blocks of thrusts. Their margins were displaced by frontal thrusts and lateral ramps/tear faults, but not re-activated as usually described in literature. One arresting feature is represented by the behaviour of the Calcare Massiccio blocks during the compressive deformations. In fact, the Calcare Massiccio olistoliths locally developed shear contacts with the embedding pelagic units, due to the contrasting mechanical behavior of the two lithologies when subjected to folding. Last, Pliocene extensional faults apparently exploited the strikes of the rotated pre-orogenic margins.