Marco Tallini

Long-term spatio-temporal hydrochemical and 222Rn tracing to investigate groundwater flow and water–rock interaction in the Gran Sasso (central Italy) carbonate aquifer

In the Gran Sasso fissured carbonate aquifer (central Italy), a long-term (2001–2007) spatio-temporal hydrochemical and 222Rn tracing survey was performed with the goal to investigate groundwater flow and water–rock interaction. Analyses of the physico-chemical parameters, and comparisons of multichemical and characteristic ratios in space and time, and subsequent statistical analyses, permitted a characterisation of the hydrogeology. At the regional scale, groundwater flows from recharge areas to the springs located at the aquifer boundaries, with a gradual increase of mineralisation and temperature along its flowpaths. However, the parameters of each group of springs may significantly deviate from the regional trend owing to fast flows and to the geological setting of the discharge spring areas, as corroborated by statistical data. Along regional flowpaths, the effects of seasonal recharge and lowering of the water table clearly cause changes in ion concentrations over time. This conceptual model was validated by an analysis of the 222Rn content in groundwater. 222Rn content, for which temporal variability depends on seasonal fluctuations of the water table, local lithology and the fracture network at the spring discharge areas, was considered as a tracer of the final stages of groundwater flowpaths.RésuméDans l’aquifère carbonaté fissuré du Grand Sasso (Italie centrale), une étude spatio-temporelle longue durée (2001–2007) par traçage hydrochimique incluant 222Rn a été réalisée dans le but d’étudier l’écoulement souterrain et l’interaction eau–roche. Des analyses des paramètres hydrochimiques, des comparaisons de ratios multiparamétriques caractéristiques dans l’espace et le temps et les analyses statistiques subséquentes ont permis une caractérisation de l’hydrogéologie. A l’échelle régionale, l’écoulement de l’eau souterraine depuis les aires de recharge jusqu’aux sources situées en limite de l’aquifère, s’accompagne d’une augmentation graduelle de la minéralisation et de la température le long du chenal d’écoulement. Toutefois, les paramètres de chaque groupe de sources peuvent s’écarter de façon significative de la tendance régionale, écarts dus à des écoulements rapides et aux caractéristiques géologiques des aires de décharge des sources, comme corroboré par les données statistiques. Le long des chenaux régionaux, les effets de la recharge saisonnière et les abaissements de la surface libre de la nappe causent clairement des changements des concentrations ioniques dans le temps. Ce modèle conceptuel a été validé par une analyse de la teneur en 222Rn dans l’eau de nappe. La teneur en 222Rn, dont la variabilité dans le temps dépend des fluctuations saisonnières de la nappe, la lithologie locale et le réseau de fractures des aires de décharge de l’aquifère, ont été considérés comme marqueurs des étapes finales des écoulements souterrains.ResumenSe llevó a cabo la traza hidroquímica espacio temporal a largo plazo (2001–2007) y el relevamiento de trazadores de 222Rn con el objetivo de investigar el flujo de agua subterránea y la interacción agua–roca en el acuífero carbonático fisurado del Gran Sasso (Italia Central). Los análisis de parámetros físico-químicos, y las comparaciones de cocientes característicos y multiquímicas en espacio y tiempo, y los análisis estadísticos subsecuentes permitieron una caracterización de la hidrogeología. En la escala regional, el agua subterránea fluye desde las áreas de recarga hacia los manantiales localizados en los bordes del acuífero, con un incremento gradual de mineralización y temperatura a lo largo de sus trayectorias de flujo. Sin embargo, los parámetros de cada grupo de manantiales pueden desviarse significativamente de la tendencia regional debido al flujo rápido y a la configuración geológica de las áreas de descarga de los manantiales, como fue corroborado por datos estadísticos. A lo largo de las trayectorias de flujos regionales, los efectos de la recarga estacional y el descenso de los niveles freáticos causa claramente cambios en las concentraciones iónicas a través del tiempo. Este modelo conceptual fue validado con un análisis del contenido de 222Rn en aguas subterráneas. El contenido de 222Rn, cuya variabilidad temporal depende de las fluctuaciones estacionales del nivel freático, la litología local y las redes de fracturas en las áreas de descarga de los manantiales, fue considerado como un trazador de las etapas finales de las trayectorias del flujo de agua subterránea.ResumoNo aquífero fissurado carbonatado de Gran Sasso (Itália central) foi efetuado um estudo com traçadores hidroquímicos e de 222Rn no espaço-tempo e a longo prazo (2001–2007), com o objetivo de investigar o fluxo de água subterrânea e a interação água–rocha. Análises dos parâmetros físico-químicos e comparações das relações multiquímicas e caraterísticas no espaço e no tempo, e subsequentes análises estatísticas, permitiram a caraterização da hidrogeologia. À escala regional, a água subterrânea flui das áreas de recarga para as nascentes localizadas nas fronteiras do aquífero, com um incremento gradual na mineralização e na temperatura ao longo do percurso. No entanto, os parâmetros de cada grupo de nascentes podem desviar-se significativamente da tendência regional, devido a fluxos mais rápidos e ao ambiente geológico das áreas de descarga das nascentes, como corroborado por dados estatísticos. Ao longo dos percursos de fluxo regionais, os efeitos da recarga sazonal e do rebaixamento do nível freático causam claramente alterações nas concentrações iónicas ao longo do tempo. Este modelo concetual foi validado por análises do conteúdo de 222Rn na água subterrânea. O conteúdo de 222Rn, para o qual a variabilidade temporal depende das flutuações sazonais do nível freático, da litologia local e da rede de fraturas nas áreas de descarga, foi considerado como um traçador dos estágios finais dos percursos de fluxo de água subterrânea.

Plio-Quaternary geology of L’Aquila – Scoppito Basin (Central Italy)

ABSTRACT We present a geological map at 1:25,000 scale of the Plio-Quaternary L’Aquila-Scoppito intermontane basin (central Italy), which corresponds to the epicentral area of the 6th April 2009 L’Aquila earthquake (Mw: 6.29). The map is derived from geological field surveys at 1:5000 scale and takes into account previously published maps. It is supported by a fine-scale LiDAR digital elevation model, paleontological analyses, 14C dating, well log analyses of deep boreholes, and geophysical data interpretation. By taking into account that the remarkable historical and present-day seismicity of the area is the result of its Plio-Quaternary geological evolution, the aim of this study is to produce a fine-scale geological map of the study area through a comprehensive analysis of the occurring Plio-Quaternary synthems and the tectonic processes that are taking place within it.

New insights into earthquake precursors from InSAR

We measured ground displacements before and after the 2009 L’Aquila earthquake using multi-temporal InSAR techniques to identify seismic precursor signals. We estimated the ground deformation and its temporal evolution by exploiting a large dataset of SAR imagery that spans seventy-two months before and sixteen months after the mainshock. These satellite data show that up to 15 mm of subsidence occurred beginning three years before the mainshock. This deformation occurred within two Quaternary basins that are located close to the epicentral area and are filled with sediments hosting multi-layer aquifers. After the earthquake, the same basins experienced up to 12 mm of uplift over approximately nine months. Before the earthquake, the rocks at depth dilated, and fractures opened. Consequently, fluids migrated into the dilated volume, thereby lowering the groundwater table in the carbonate hydrostructures and in the hydrologically connected multi-layer aquifers within the basins. This process caused the elastic consolidation of the fine-grained sediments within the basins, resulting in the detected subsidence. After the earthquake, the fractures closed, and the deep fluids were squeezed out. The pre-seismic ground displacements were then recovered because the groundwater table rose and natural recharge of the shallow multi-layer aquifers occurred, which caused the observed uplift.

Geometry and kinematics of the Montelanico-Carpineto Backthrust (Lepini Mts., Latium) in the hangingwall of the early Messinian thrust front of the central Apennines: implications for the Apennine chain building

The paper updates knowledge on the Montelanico-Carpineto Backthrust, which is confined in the Lepini Mts. thrust sheet, at the hangingwall of the Neogene Latina Valley Thrust Front. The local stratigraphic setting consists of a pre-orogenic succession of Mesozoic carbonates from the Latium-Abruzzi platform Auct. The carbonates are paraconformably overlain by Miocene ramp limestones, which evolve upwards into planktonic marls. The Sub-Ligurian unit thrusted over this dominantly carbonate succession. In the Latina Valley, siliciclastic turbidites (Frosinone Formation Auct. ), which evolved from the above-mentioned Miocene units, constitute the upper Tortonian foredeep deposits, now preserved in the footwall of the Lepini Mts. thrust sheet. In the Segni-Montelanico area, conglomerates, unconformably overlying the carbonate bedrock and coeval with the Frosinone Formation, are interpreted as late Tortonian thrust-top deposits (Gavignano and Gorga unit). The Lepini Mts. ridge has two series of distinctive tectonic features: the first is related to the Neogene shortening events due to the Apennine chain building; the other results from Plio-Quaternary extensional events associated with the collapse of the Tyrrhenian margin. The Montelanico-Carpineto Backthrust, as evidenced by the structural survey, is a compressive fault plane dipping 45°–50° towards NE with a SW-verging dip-slip kinematics. The fault has an offset of about 700 m, ramp geometries and a cut-off of about 20°. The Montelanico-Carpineto Backthrust and the Latina Valley Thrust Front define a pop-up structure. The presumable age of the Montelanico-Carpineto Backthrust is the early Messinian, because the late Tortonian Gavignano and Gorga unit is involved in its brittle shear zone. This implies that the formation of the Montelanico-Carpineto Backthrust and of the related pop-up structure is coeval with the early Messinian thrusting of the Lepini Mts. thrust sheet upon the geodynamic propagation of the central Apennine chain-foredeep-foreland system.

A record of changes in the Gran Sasso groundwater before, during and after the 2016 Amatrice earthquake, central Italy

We performed continuous recordings (May 2015 – January 2017) of hydraulic pressure and electrical conductivity of groundwater in the 190 m-long horizontal S13 borehole drilled next to the deep underground laboratories of Gran Sasso (LNGS-INFN), located in the core of the Gran Sasso carbonate aquifer (central Italy) at a distance of about 39 km south-eastward from the 24 August 2016 Amatrice earthquake (6.0 Mw) epicenter. Using a 3-channel, 24-bit ADC we achieved a sampling rate of groundwater physical properties up to 50 Hz for each channel. We focused on the analysis of data recorded before, during and after the Amatrice earthquake, describing and discussing in detail the evidence for significant hydraulic pressure and electrical conductivity anomalies recorded before the main shock. We identified unambiguous signals in the hydraulic pressure data starting on 19 August, i.e. five days before the 24 August mainshock. A more careful analysis allowed us to detect the inception of a weak change up to 40 days before the Amatrice earthquake and a significant variation in the electrical conductivity data about 60 days before. The data revealed highly dynamic aquifer behaviour associated with the uprising of geogas probably related to the preparation stage of the Amatrice earthquake.

Plio-Quaternary geology of the Paganica-San Demetrio-Castelnuovo Basin (Central Italy)

ABSTRACT We present the geological map at 1:25,000 scale of the Plio-Quaternary Paganica-San Demetrio-Castelnuovo Basin corresponding to the epicentral area of the 6 April 2009 Mw: 6.29 L’Aquila earthquake. The map focuses on the relationships between the active tectonics and the Plio-Quaternary deposits and on the early evolution of this continental basin. Fine-scale geological field surveys, coupled with paleontological data, facies analyses, well logs and geophysical data interpretation, allowed to better understand the stratigraphy and to review the previously described stratigraphical units, resulting in the definition of eight synthems, spanning from late Piacenzian to Holocene. More precisely, the occurrence of a Caspiocypris species flock (ostracods) at the base of the sedimentary infill of the basin formed by a lacustrine system, suggests that the onset of deposition started in the late Piacenzian. The lacustrine system disappeared around the Gelasian/Calabrian transition, while the subsequent evolution of the sedimentary basin was characterized by the presence of fluvial and alluvial fan systems progressively entrenched into the lake deposits. The results of the above-mentioned activities are summarized in the attached geological map, where the Plio-Quaternary synthems and the active normal faults accountable for the significant seismicity were highlighted.

2D site response analysis of a cultural heritage: the case study of the site of Santa Maria di Collemaggio Basilica (L’Aquila, Italy)

The Santa Maria di Collemaggio Basilica is an important cultural heritage site and exemplifies Romanesque-Gothic art in the Abruzzo region (central Italy). Erected in the second half of the XII century, the Basilica was severely damaged during the April 6, 2009 L’Aquila earthquake (MW 6.1). In particular, the area of the transept collapsed causing the dome to fall. A refined two-dimensional (2D) geotechnical model was built representing a section that includes the Basilica, in order to better understand the soil response of the Basilica site. The subsoil model was constrained using the geophysical and geotechnical data collected from the seismic microzonation studies, the reconstruction of private damaged buildings and other technical and scientific studies realized in the L’Aquila basin and in the area of the Basilica before and after L’Aquila earthquake. 2D site response analyses were performed to verify the presence of local site effects by comparing simulated versus experimental transfer functions. Moreover, a frequency–wavenumber (f–k) analysis was executed with the aim of evaluating the occurrence of surface waves generated within the basin. 2D seismic effects involve significant amplification in the period range of engineering interest, therein providing an appropriate elastic response spectrum for the restoration of the Basilica.

Sessione S 30. Groundwater resource among human needs, reuse and environmental requirements

Abstract from 88th Congress of the Italian Geological Society, 2016-09-07 - 2016-09-09, NaplesAbstract from 88th Congress of the Italian Geological Society, 2016-09-07, 2016-09-09, Naplesbook Edited by D. Calcaterra, S. Mazzoli, F.M. Petti, B. Carmina & A. Zuccari doi: 10.3301/ROL.2016.79

The Seismic Site Characterization of Palazzo Centi in L’Aquila City Centre: The Case Study of a Historical Building Damaged by the April 6th 2009 Earthquake

An extensive geological, geotechnical and geophysical investigation was performed in L’Aquila city centre to restore Palazzo Centi, a historical building, damaged by the April 6, 2009 L’Aquila earthquake. This site investigation consisted of punctual and linear tests that allowed to define a detailed 3D model of the subsoil, irregularly affected by some peculiar conditions and characterized by low and variable values of the shear wave velocity V S in the near surface volume. In particular, the variable thickness of the upper fine-grained residual soils probably determined different ground motion amplifications during the main shock.