Seismic hazard for the Trans Adriatic Pipeline (TAP). Part 2: broadband scenarios at the Fier Compressor Station (Albania)

AbstractTo ensure environmental and public safety, critical facilities require rigorous seismic hazard analysis to define seismic input for their design. We consider the case of the Trans Adriatic Pipeline (TAP), which is a pipeline that transports natural gas from the Caspian Sea to southern Italy, crossing active faults and areas characterized by high seismicity levels. For this pipeline, we develop a Probabilistic Seismic Hazard Assessment (PSHA) for the broader area, and, for the selected critical sites, we perform deterministic seismic hazard assessment (DSHA), by calculating shaking scenarios that account for the physics of the source, propagation, and site effects. This paper presents a DSHA for a compressor station located at Fier, along the Albanian coastal region. Considering the location of the most hazardous faults in the study site, revealed by the PSHA disaggregation, we model the ground motion for two different scenarios to simulate the worst-case scenario for this compressor station. We compute broadband waveforms for receivers on soft soils by applying specific transfer functions estimated from the available geotechnical data for the Fier area. The simulations reproduce the variability observed in the ground motion recorded in the near-earthquake source. The vertical ground motion is strong for receivers placed above the rupture areas and should not be ignored in seismic designs; furthermore, our vertical simulations reproduce the displacement and the static offset of the ground motion highlighted in recent studies. This observation confirms the importance of the DSHA analysis in defining the expected pipeline damage functions and permanent soil deformations

Caratterizzazione qualitativa dei serbatoi acquiferi

Le caratteristiche quantitative e qualitative del patrimonio idrico sotterraneo di un territorio (acquiferi) dipendono da molteplici fattori che possono essere suddivisi in due gruppi principali: Il primo gruppo comprende fattori naturali, o primari, come quelli geologi che condizionano le caratteristiche geometriche degli acquiferi (es. spessore, estensione), idrauliche (porosità, permeabilità), ed idrogeochimiche, conseguenza del contatto tra la matrice solida (sedimenti) e fluidi (acqua). Il secondo gruppo, invece, include fattori antropici, o secondari, che possono provocare, da una parte, il degrado quantitativo delle risorse idriche sotterranee (come gli emungimenti eccessivi e non controllati per soddisfare, ad esempio, le esigenze acquedottistiche, agricole ed industriali) e, dall’altra parte, possono accelerare i processi di degrado qualitativo causato dall’eccessivo aumento delle fonti potenziali di inquinamento, sia puntuali che diffuse. In particolare, nel sottosuolo ferrarese, a causa della complessa evoluzione geologica, le risorse idriche sotterranee sono fortemente condizionate e limitate sia qualitativamente che quantitativamente dalla presenza di sedimenti permeabili deposti in ambienti lagunari, deltizi o marini. In questo tipo di sedimenti, si trovano comunemente acque primarie (i.e. sinsedimentarie), generalmente con caratteristiche salmastre che presentano, pertanto, bassi valori di resistività elettrica, generalmente minori di 5 Ohm*m, ed elevata salinità. Sulla base di numerose colonne stratigrafiche relative a pozzi per acqua e per la ricerca di idrocarburi (AGIP, 1972; SQUARZANTI, 1980) è stato possibile ricostruire, per la prima volta, l'andamento della zona di dispersione dove si verifica il passaggio graduale tra acqua dolce ed acqua salmastra, ponendo il limite in corrispondenza di valori di salinità pari a 1 g/l. Tale limite si trova a profondità variabili da pochi metri dal piano campagna, nell'area di Casaglia (20 m), a profondità di circa 50 m, nella zona di Baura, ad i 300 m, nei pressi di Copparo (VILLA et alii, 1976; SQUARZANTI, 1980). Negli anni successivi, sono state realizzate poche ricerche di carattere locale che generalmente hanno affrontato problematiche di carattere idrogeologico ed idrogeochimico. La ricerca qui descritta ha avuto come scopo principale la ricostruzione, per l'intero territorio provinciale, del comportamento e dell'evoluzione, sia idrodinamica che geochimica, delle risorse idriche sotterranee. A tal fine, è stato utilizzato un protocollo di lavoro che comprende l'analisi integrata di dati di carattere stratigrafico, idrogeologico e geochimico. Sulla base dei dati stratigrafici e fino alla profondità massima di 200 m, nel sottosuolo ferrarese sono state distinte cinque unità idrogeologiche corrispondenti all’acquifero a falda libera (A0), all'acquifero A1, generalmente in pressione e, agli acquiferi più profondi A2, A3 e A4, sempre in pressione. Le caratteristiche geologiche di questi acquiferi sono state descritte in precedenza (vedi Cap. I, § 1.3). Per la definizione della rete di monitoraggio dei pozzi che riesce a descrivere il comportamento idrodinamico e geochimico degli acquiferi ferraresi in pressione, ci si è basati sulla raccolta e sull’elaborazione di dati provenienti dall'archivio dell'ARPA e raccolti sia dalla rete di controllo attiva che da quella inattiva. Inizialmente, sulla base dell’elaborazione dei dati stratigrafici ed adottando criteri geometrici, litologici e di “capacità idrica” delle diverse formazioni, sono stati individuati i principali corpi acquiferi. Successivamente, ed utilizzando come criteri assoluti la descrizione litologica di ogni singolo pozzo e la posizione dei filtri, è stata effettuata una divisione ed una scelta dei pozzi per ogni corpo acquifero come questo è stato definito nella fase precedente. In tal modo, sono stati esclusi tutti i punti di misura e/o di campionamento per i quali non esiste una dettagliata descrizione stratigrafica, la posizione dei filtri oppure nel caso in cui i pozzi fossero filtrati in più acquiferi. Questo approccio metodologico ci ha permesso di distinguere nove pozzi filtrati esclusivamente nell’acquifero A1; sette pozzi in quello A2; un pozzo nell’acquifero A3 ed un pozzo in quello A4. Nei pozzi individuati esistono misure sistematiche della soggiacenza (profondità dell'acqua dal piano campagna), relative al periodo 1977-1998, con frequenza semestrale, mentre, solamente per alcuni di essi esistono informazioni relative allo stato chimico delle acque

Rapti-Caputo, D. (2007): Palaeo-channels and groundwater vulnerability: some considerations.

In order to define the role played by both superficial and buried palaeo-channels within the alluvial plain of the River Po, Northern Italy, aimed to determine the intrinsic vulnerability of the aquifer systems, geomorphological, lithological, hydrogeological and geochemical data have been analysed. In particular, the relationships of these sedimentary bodies with the intrinsic vulnerability and the diffusion of polluting substances in the underground water resources have been investigated. In the eastern sector of the Po Plain and especially in the broader area surrounding Ferrara, the dominant geomorphological features are the numerous palaeo-channels. Along the natural levees of these abandoned river courses several archaeological and ancient sites were established. The space distribution of these prevailingly sandy bodies strongly influences the hydrodynamic behaviour of the aquifers as, for example, the geometrical characteristics of the superficial unconfined hydrogeological units. Indeed, along the axis of these geomorphological features the intrinsic vulnerability has been estimated to be high to extremely high (70-90%). In fact, in this superficial aquifer, important concentrations of chlorides have been detected and especially the sulphates and nitrates exceed the drinkableness limits, therefore indicating the qualitative decay of this resource mainly due to farming activities. The occurrence of sandy bodies also influences the vulnerability of the underlying confined aquifer that represents the main source exploited for the waterworks of the surrounding territory. When the axis of the principal palaeo-channels coincides with the present-day hydrographic network, as in the case of the Po di Volano, a hydraulic barrier with constant pressure is generated. As a consequence, the continuous mixing phenomena occurring between superficial and underground waters can either improve or worsen the quality of the water resources. Moreover, in this complex system, the determination of the intrinsic vulnerability of the aquifer bodies is one of the fondamental parameters to be determined before any strategic decision is taken for the integrated managment and protection of the underground resources and the environment

Caratterizzazione geochimica dell’acquifero alluvionale della piana di Licata (AG)

The preliminary results concerning the hydrodynamic and geochemical conditions of the underground water resources of the region surrounding Licata (Agrigento province, Sicily) are presented. The research was focused on the unconfined aquifer (or locally semiconfined) developed in the Quaternari deposits of the Licata plain. The evolution of the Salso river and the coastal dynamics, characterised by transgresions and coast-line retreats, qualitatively and quantitatively influenced the underground water resources. In this complex geological contest, also the anthropogenic activities played a crucial role, especially the farming activity as largely testified by the occurrence of numerous greenhouses that cover most of the plain. The analysis of thermopluviometric data concernine the last 75 year allowed to obtain inferences on the climatic evolution of this region characterised by a mean annual temperature of about 18 °C of mean annual precipitations of only 454 mm. The principal feeding of the aquifer is due to infiltration from precipitations and lateral outflow from the Salso river. The high salinity of the river especially during Summer periods and the intense farming activities played a crucial role for the quality of the aquifer

Evoluzione geochimica e modalità di gestione di un acquifero alluvionale

In the eastern hydrographic basin of the Po river, Northern Italy, the underground water circulation is strongly influenced by the recent geological and palaeogeographic evolution of the region, while the qualitative characteristics of the water are controlled by the depositional environment (continental, marine, etc.). Within such complex sedimentary environments, the exploitation mode plays a crucial role for the preservation of the overall aquifer quality. In order to evaluate the influence of the exploitation on the geochemical characteristics of the underground resources, hydrodynamic (piezometric level) and hydrochemical (Ph, temperature, electrical conducibility, content in HCO3, Ca, NH4, Fe, Mn, SO4, Cl, NO3, Cl, F and Br) data have been collected from the first unconfined aquifer and analysed. The investigated area corresponds to the territory surrounding Ferrara town. The elaboration of these data based on classical hydrogeological and hydrogeochemical methods, integrated with isotopic analyses allows a) to separate the principal hydrogeochemical facies, b) to recognise the occurrence of mixing phenomena between the water of the exploited aquifer and the salty water of the underlying aquifer, c) to infer about the equilibrium between the amount of pumping and the quality of the water

Some remarks on water resources degradation and ground fissures formation in Thessaly, Greece

(i.e. low precipitations) affecting the Aegean Region and the huge increase of the cotton cultivation in large sectors of Thessaly, central Greece, forced people to search for new water resources to provide the needs. Accordingly, during the seventies and eighties, the synergy of the natural phenomenon with the inappropriate agricultural choice, was coupled with the drilling of an almost uncontrolled number of boreholes across the entire area. These water-wells that mainly exploit the alluvial multi-aquifer system of the Larissa Plain caused a significant downdrop of the piezometric level that critically exceeded the capacity to regenerate the underground natural hydraulic conditions. As a consequence, a quantitative and sometimes qualitative degradation of the water resources occurred. During the nineties, numerous ground fissures have been documented within the Larissa Plain. These superficial features have locally roduced important damages by creating open fractures in houses, stores and infrastructures, dislocations and hollows across roads and even caused a road accident. The occurrence of the phenomenon more than once, the associated damages and the awareness of the general seismogenic character of Thessaly deeply frightened the inhabitants of the region and their Authorities. A common opinion is that the production of fissures is straightforwardly and directly elated to the general lowering of the piezometric level (Soulios, 1997). In the present research, we revised all available data in order to better understand the phenomenon and the cause-effect relationships

Some remarks on water resources degradation and ground fissures formation in Thessaly, Greece

During the last decades, the concomitance of a relatively dry period (i.e. low precipitations) affecting the Aegean Region and the huge increase of the cotton cultivation in large sectors of Thessaly, central Greece, forced people to search for new water resources to provide the needs. Accordingly, during the seventies and eighties, the synergy of the natural phenomenon with the inappropriate agricultural choice, was coupled with the drilling of an almost uncontrolled number of boreholes across the entire area. These water-wells that mainly exploit the alluvial multi-aquifer system of the Larissa Plain caused a significant downdrop of the piezometric level that critically exceeded the capacity to regenerate the underground natural hydraulic conditions. As a consequence, a quantitative and sometimes qualitative degradation of the water resources occurred

Climatic and anthropogenic impact on underground water quality: an example from Agrigento province (Sicily, Italy)

The alluvial plain of Licata (southern Sicily, Agrigento province) has been investigated to evaluate the influence of the human activities and that of the climatic changes in the hydrological cycle in terms of qualitative and quantitative impact on the groundwater resources. In this area, the evolution of the Salso river (in Italian ’salty river’) and the coastal dynamics, characterised by consecutive transgresions and retreats of the coast-line, qualitatively and quantitatively influenced the underground water resources. In this complex geological contest, also the anthropogenic activities played a crucial role, especially the farming activity as largely testified by the occurrence of numerous greenhouses that cover most of the plain. The analysis of thermopluviometric data concerning the last 75 year allowed to obtain inferences on the climatic evolution of this region characterised by a mean annual temperature of about 18 C and mean annual precipitations of only 454 mm. In particular, during the last 24 years a 12 % decrease of the precipitation with respect the previous period of observation is observed together with the increase of the temperature of the air about 1 C. The research was focused on the unconfined, mainly sandy, aquifer developed in the Quaternary deposits of the Licata plain. The water depth of this aquifer is between to 0.3 to locally 5 m from the surface and the principal alimentation occurs via infiltration from precipitations and lateral outflow from the Salso river. The high salinity of the river especially during Summer periods and the intense farming activities played a crucial role for the quality degradation of the aquifer

Geochemical composition of the underground resources in the Ferrara plain (northern Italy)

In the present work, the results of the hydrodynamical and hydrochemical analysis of the multiaquifer alluvial system existing in the eastern sector of the Po plain are presented allowing to define the evolution of the aquifer system. In particular, based on the analysis of the water depth, it is possible to measure the influence on the piezometric level of the pumping rate. It is also possible to observe strong fluctuations of the piezometric level in the bore-holes close to the Po River, due to variations of the hydrometric level and of the pumping rate from the aquifer system. During the last years, in some of the wells, a progressive and continuous increase of the piezometric level likely attributed to the decrease of the exploration rate of the aquifer has been observed. Based on the analysis of the hydrochemical data it is also possible to define a) the principal geochemical facies of the underground water; b) the occurrence of mixing phenomena between different water types; c) the natural ionic concentration of the water and d) the occurrence of contamination phenomena