Roma Tre University

In this paper, we applied an Horizontal to Vertical (HV) spectral ratio analysis to ambient vibration data aiming at the preliminary seismic response identification of a masonry building, characterized by a significant complexity in terms of geometry and elevation. The building is monitored in the aim of the PON01-02710 MASSIMO project. We performed other standard Fourier analyses computing the Power Spectral density (PSD) and the Cross-Power Spectral Density (CPSD) of the signals. The obtained results demonstrates how HV may be very useful for a rapid screening of buildings in those complex cases such as structures belonging to the cultural heritages, and we concluded that noise measurements may indeed contribute to a detailed real dynamic response definition of a system. However, another main objective of this study is the integration of the results obtained by means of the classical aforementioned Fourier analysis techniques with those coming from the application of time-frequencies analyses: the Short-Time Fourier Transform (STFT) and the complex wavelet transform (CWT) which uses the modified complex Morlet function. In fact, there are few case studies of joint application of these different techniques to masonry heritages. Thus, the study provides the opportunity for integrating them and primarily, for exploring capabilities of wavelet transform in Structural Health Monitoring (SHM).

This paper illustrates a geographic information system (GIS) supported methodology for the assessment of landslide susceptibility. The methodology involves four operational steps: survey, site analysis, macro- area analysis and susceptibility analysis . The Survey includes the production (or acquisition) of a large-scale litho-technical map, a large-scale geomorphological map, a detailed inventory of past and present land- slide events, and a high resolution DTM (Digital Terrain Model. Site analysis leads to the definition of discriminating parameters (commonly, lithological and morphometric conditions necessary but not suffi- cient to trigger a landslide of a given type) and predisposing factors (conditions that worsen slope stability but are not sufficient to trigger a landslide of a given type in the absence of discriminating parameters ). The different predisposing factors are subdivided into classes, whose intervals are established by descriptive, statistical analysis of landslide inventory data. A numerical index, based on the frequency of landslide occurrence, quantifies the contribution of each class to slope instability. Macro-area analysis includes the generation of Litho-Morphometric Units (LMU) by overlaying discrimina- ting parameters , manual drawing of LMU envelopes ( macro-areas ), generation of predisposing factor maps from the spatial distribution of predisposing factors , and heuristic weighting of predisposing factor indices. Susceptibility analysis includes the generation of Homogeneous Territorial Units (HTU) by overlaying macro- areas and predisposing factor maps , and the application of a susceptibility function to the different HTU. The resulting values are normalized before the generation of the landslide susceptibility maps . The methodo- logy has been applied to the Fiumicino River catchment, located in the western side of Latium Apennine (Central Italy) between 200 and 1300 m a.s.l. and developed on Late Miocene calcarenites, sandstones with clay intercalations, and marls. The resulting landslide susceptibility maps will be employed in envi- ronmental management. They also represent the preliminary step for the assessment of landslide hazard and risk

We investigate shear wave polarization in the Hayward fault zone near Niles Canyon, Fremont, CA. Waveforms of 12 earthquakes recorded by a seven-accelerometer seismic array around the fault are analysed to clarify directional site effects in the fault damage zone. The analysis is performed in the frequency domain through H/V spectral ratios with horizontal components rotated from 0◦ to 180◦, and in the time domain using the eigenvectors and eigenvalues of the covariance matrix method employing three component records. The near-fault ground motion tends to be polarized in the horizontal plane. At two on-fault stations where the local strike is N160◦, ground motion polarization is oriented N88 ± 19◦ and N83 ± 32◦, respectively. At a third on-fault station, the motion is more complex with horizontal polarization varying in different frequency bands. However, a polarization of N86 ± 7◦, similar to the results at the other two on-fault stations, is found in the frequency band 6–8 Hz. The predominantly high-angle polarization from the fault strike at the Hayward Fault is consistent with similar results at the Parkfield section of the San Andreas Fault and the Val d’Agri area (a Quaternary extensional basin) in Italy. In all these cases, comparisons of the observed polarization directions with models of fracture orientation based on the fault movement indicate that the dominant horizontal polarization is near-orthogonal to the orientation of the expected predominant cracking direction. The results help to develop improved connections between fault mechanics and near-fault ground motion.

Across the Pernicana fault on Mt. Etna, Di Giulio et al. (2009) found a significant and persistent variation in the polarization angle when moving from the fault hangingwall to the fault footwall. This effect was recurrently observed on several stations and both on volcanic tremor and ambient noise. In this work we propose an interpretation of this variation, calculating the brittle deformation pattern associated to the fault through the package FRAP3 (Salvini, 2002). The Pernicana fault system represents the Northern boundary of the main flank instability of Mt Etna volcano, from the eastern to the south-western portions of the volcanic edifice, where down-slope movements are produced with significant slip rates. It reaches a length of more than 18 km, and the kinematics is mainly left-lateral even though a transtensive component is locally present due to the flank instability. The western portion of the Pernicana fault system, striking N90° and close to Piano Pernicana area, is characterized by the most intense deformation (Acocella and Neri, 2005). In this area Di Giulio et al. (2009) performed volcanic tremor and noise measurements on a dense grid along and across the fault zone, in order to calculate the local polarization azimuths. The Horizontal-to-vertical spectral ratios (HVSR) showed large directional resonances of horizontal components within the damaged fault zone, resonance everywhere occurring around 1 Hz. Conversely the polarization azimuth varies from N160 at stations installed on the fault hangingwall to N120 at stations lying in the fault footwall. Previous studies (e.g. Pischiutta et al., 2011) successfully related that ground motion horizontal polarization in fault zones can be produced by the brittle deformation fields in the damage zone, with a predominant near-perpendicular relation between fractures and polarization strikes. Given this premise, we modeled the fracture field expected for the Pernicana fault system in the Piano Pernicana sector. We assumed a pure left-lateral kinematics in the hanging wall, while in the footwall that is part of the flank instability we added a slight trantensive component to the strike-slip movement. As a result, in the fault hanging wall the synthetic cleavage has a higher probability to develop, with an orientation toward N75 direction. Meanwhile, the extensional fractures appear to be the dominating fracture systems in the fault footwall, with a modeled N40 orientation. As a consequence, we ascribe the variation in polarization azimuth found by Di Giulio et al (2009) to the distribution of the fracture systems, which appear to be different in the hangingwall and in the footwall. Consistently with previous studies, a near-perpendicular relation between wave polarization and the dominant fracture field is recognized on the Pernicana fault, due to the reduction of rock stiffness caused by the presence of fractures: horizontal vibrations are far more pronounced in the direction perpendicular to fractures.

Several recent studies indicate that ambient noise and seismic signals in fault zones tend to be polarized on the horizontal plane with a clear preferred orientation direction. Here we present a summary of past experiments as well as new study cases showing evidence of this effect: the Val d’Agri, the Pernicana and the Paganica faults in Italy, and the Hayward fault in California. We also analyze data recorded by the HRSN network at the Parkfield section of the San Andreas fault and find that stations MM and GH that are close to the fault damage zone show a similar persistent and marked polarization effect. The approach combines the H/V technique in the frequency domain with the covariance matrix diagonalization method in the time domain. Common features are: i) a high stability of results at each site, independently of the nature and location of the source of seismic signals, ii) a characteristic polarization for each fault, and iii) the preferred polarization is close to the fault-normal direction, rather than being fault parallel as would be expected for generation of fault zone trapped waves. In previous papers, the role of fluid-filled microcracks in the damage zone was hypothesized. We have then explored an hypothesis based on the fracture field orientation in the fault damage zone by applying the package FRAP3 (Salvini, 2002) to model the brittle deformation field expected for the studied faults. We have found a consistent orthogonal relation between the observed polarizations and the orientation of the predicted synthetic fracture systems. When anisotropy studies are available, the horizontal ground motion polarization is consistently found to be perpendicular to the fast wave splitting component. The results may reflect reduced stiffness in the fault-normal direction produced by the presence of damage fault zone rocks.

Many recent studies indicate that ambient noise and seismic signals in fault zones tend to be polarized on the horizontal plane with a predominant orientation. Here we present a summary of past experiments as well as new study cases showing evidence of this effect. The approach combines the H/V technique in the frequency domain with the covariance matrix diagonalization method in the time domain. Common features are: i) a high stability of results at each site, independently of the nature and location of the source of seismic signals, ii) a predominant polarization characteristic for each fault, and iii) polarization is not parallel to the fault strike as it would be expected for fault-trapped wave generation. In previous papers, a role of fluid-filled microcracks in the damage zone was hypothesized. If this is true, a correlation is expected between seismic anisotropy and polarization. In the studied faults, when anisotropy results are available, the horizontal ground motion polarization is found to be perpendicular to the fast wave splitting component, confirming the role of fluid-filled microcracks in the damage zone. We have then checked this interpretation in terms of the fracture field orientation in the damage zone by applying the package FRAP3 (Salvini, 2002) to model the brittle deformation field expected in the damage zone of the studied faults. We have found a consistent orthogonal relation between the observed polarizations and the orientation of the predicted fracture systems. The quick and relatively inexpensive character of the method encourages to further tests for an extensive application to many fields of theoretical and applied geophysics.

In this study numerical simulations of reactive transport in an off-shore deep saline aquifer for the geological sequestration of carbon dioxide are presented and discussed. The main goals are to assess: i) the CO2 injection impact in the reservoir and ii) the cap-rock stability, both being strategic requisites for feasibility studies that are about to be started in Italy. The stratigraphic succession is characterized by a sedimentary succession: from Triassic anhydrites to Jurassic Tuscan calcareous units, up to Cretaceous calcarenites, belonging to the Liguride units, and Quaternary shallow marine sediments. Stratigraphic data from a deep well indicate that below an 1,800 m thick cap-rock, constituted by allochtonous marly calcarenites and clay marls, a regional deep saline aquifer is present. This aquifer, hosted in six Late Triassic to Early Jurassic formations, belonging to the Tuscan Nappe units, consists of porous limestone (mainly calcite) and marly limestone deposits at 1900-3100 m b.s.l. A common problem working with off-shore closed wells, where only the well-log information are available, is that to obtain reliable physico-chemical parameters (e.g. petrophysical and mineralogical) to be used for numerical simulations. Available site-specific data include only basic physical parameters such as temperature, pressure, and salinity of the formation waters. Bulk and modal mineralogical composition were obtained after sampling each formation in contiguous on-shore zones. Mineralogy was determined by X-Ray diffraction analysis coupled with Rietfield refinement. The latter was performed using Maud v2.2. The surface reactive area of minerals was assumed as geometric area of a truncated sphere calculated on the basis of Scanning Electronic Microscopy analysis. Porosity and permeability were inferred by the well-log data along with the use of boundary conditions such as surficial measurements and temperature profiles. The chemical composition of the aquifer pore water is unknown. As a consequence, this was calculated by batch modeling, assuming thermodynamic equilibrium between minerals and a NaCl (0.45 M) equivalent brine at reservoir conditions (up to 118 °C and 300 bars). The reconstructed dataset represented the base of numerical simulations to evaluate the potential geochemical impact of CO2 storage and to quantify water-gas-rock reactions. Three dimensional simulations were performed by the TOUGHREACT code via the implementation to the source code and the correction of the chemical parameters at the theoretical CO2 injection pressure. A re-interpretation of the available seismic reflection data was carried out to: i) define the 3D geometry, and ii) evaluate the volume of the geological structure potentially suitable for CO2 storage. In particular the main surfaces where physicochemical modeling was applied, i.e. the top and the bottom of the cap-rock units and the spill point surface, to better define the 3D geometry of the potential injection reservoir, were reconstructed. Reactive transport simulations were conducted under multiphase advection, aqueous diffusion, gas phase participation in multiphase fluid flow and geochemical reaction in non-isothermal conditions. Feedbacks between flow and geochemical processes were taken into account to evaluate changes in porosity and permeability as kinetic reactions were proceeding. Twenty years of CO2 injection at the rate of 1.5 Mt/year were simulated, whereas water-gas-rock interactions between CO2-rich brines and minerals over a period of 100 years were performed. Preliminary results suggest that injected CO2 can safely be retained in the reservoir by mineral trapping and that the cap-rock can be considered as efficient barrier.

CO2 Capture & Storage in saline aquifers is presently one of the most promising technologies for reducing anthropogenic emissions of CO2. In these sites the short-longterm consequences of CO2 storage into a deep reservoir can be predicted by numerical modelling of geochemical processes. Unfortunately a common problem working with off-shore closed wells, where only the well-log information are available, is to obtain physico-chemical data (e.g. petrophysical and mineralogical) needed to reliable numerical simulations. Available site-specific data generally include only basic physical parameters such as temperature, pressure, and salinity of the formation waters. In this study we present a methodological procedure that allows to estimate and integrate lacking information to geochemical modelling of deep reservoirs such as: i) bulk and modal mineralogical composition, ii) porosity and permeability of the rock obtained from heat flow measurements and temperature, iii) chemical composition of formation waters (at reservoir conditions) prior of CO2 injection starting from sampling of analogue outcropping rock formations. The data sets in this way reconstructed constitute the base of geochemical simulations applied on some deep-seated Italian carbonatic and sandy saline aquifers potentially suitable for geological CO2 storage. Numerical simulations of reactive transport has been performed by using the reactive transport code TOUGHREACT via pressure corrections to the default thermodynamic database to obtain a more realistic modelling. Preliminary results of geochemical trapping (solubility and mineral trapping) potentiality and cap-rock stability as strategic need for some feasibility studies near to be started in Italy are here presented and discussed.

CO2 Capture & Storage (CCS) is presently one of the most promising technologies for reducing anthropogenic emissions of CO2. The numerical modeling procedures of geochemical processes are one of the few approaches for investigating the short-long-term consequences of CO2 storage into a deep reservoir. We present the results of a new approach for the reconstruction of thermo-physical properties of an off-shore deep well (situated in the medium Tyrrhenian Sea, only 5 miles from the coast, in the frame of a distensive and relatively high heat flux regime as a whole,with good outcrops, on-shore, of its stratigraphy includes six Late Triassic-Early Jurassic carbonatic formations at the depth of 2500-3700 m b.s.l). We used the well-log coupled with temperature profile and new mineralogical analyses of the outcrops geological formations, being the original core data lacking. This kind of procedure is new as a whole, and it is useful to create background petro-physical data, for reservoir engineering numerical simulations both of mass-transport and geochemical as well as geo-mechanical, in order to asses its general properties, without re-opening the well itself for industrial use, such as CO2 geological storage. The profile of thermal capacity and conductivity, as well as porosity and permeability resulted very well constrained and detailed for further numerical simulation uses. Porosity is a very important parameter for reservoir engineering, mainly for numerical simulations including geochemical modelling, being strongly necessary for CO2 geological storage feasibility studies, because it allows to compute: i) the reservoir storage capacity for each trapping mechanisms (some algorithms are discussed in the presentation) and ii) the water/rock ratio (one of the input parameter requested by the geochemical software codes). A common problem, working with closed wells with, available the well-log report only, is to obtain data on the thermo-physical properties of the rock. Usually the available well-log report the temperature profile measured during drilling, the mud-loss and some other information on water and gas phase presence. In this work we present a procedure that allow to estimate porosity and permeability of the rock formation from the well-log data joint with a rough mineralogical analyses of the corresponding geological formations outcrop with the use of a boundary condition such as shallow heat flow measurements; a similar approach were presented from some authors that dealt with similar problems e.g. Singh V.K., (2007). The analyses of the rock samples proceed by using i) petro-graphical analyses; ii) calcimetry with Dietrich-Fruhling apparatus in order to analyse the carbonate content of each sample; iii) XRD Rietveld analyses in order to quantify the major mineralogy of each sample and to apply the dolomite correction to the results of calcimetry determination. Rietveld quantification procedure were performed by using Maud v 2.2.; iv) SEM analyses have been accomplished later in details. Successively, hints about the subsequent geochemical modelling approach are presented. Chemical composition of the aquifer pore water has been has been inferred by batch modeling assuming thermodynamic equilibrium between minerals and a NaCl equivalent brine at reservoir conditions (up to 70 °C and 200 bar). Numerical simulations has been carried out by the PRHEEQC (V2.11) Software Package via corrections to the code default thermodynamic to obtain a more realistic modeling.

Stabilize and reduce the atmospheric concentration of anthropogenic greenhouse gases is one of the principal goal that have to be accomplished in short time, in order to reduce the climate changes and the global warming, following the World Energy Outlook 2007 program by IEA. The most promising remedy, proposed for large CO2 sources like thermoelectric power plants, refineries and cement industries, is to separate the flue gas capturing the CO2 and to store it into deep sub-surface geological reservoirs, such as deep saline aquifers, depleted oil and gas fields and unminable coal beds. Among these options, deep saline aquifers are considered the reservoirs with the larger storage potentiality, as a consequence of a wide availability with respect to deep coal seems, depleted oil fields and gas reservoirs. The identification of a possible storage site necessarily passes through the demonstration that CO2 can be injected in extremely safe conditions into geological deep formations, with impermeable caprock above the aquifer/s, which physic-chemical-mineralogical conditions are useful to a better mineral and solubility trapping as well as the hydrodynamic or physical/ structural ones. In order to support the identification of potential storage reservoirs in Italy, INGV jointly with CESI RICERCA S.p.A. accomplished a detailed reworking of available geological, geophysical, geochemical and seismological data, in order to support the existing European GESTCO as well as the CO2GeoCapacity projects. Aim of this work is to establish some site selection criteria to demonstrate the possibility of the geological storage of CO2 in Italy, even if it is located in an active geodynamical domain. This research started from the study of 7575 wells drilled on Italian territory during the last 50 years for gas/oil and geothermal exploration. Among this data-set as a whole, only 1700 wells (deeper than 800 m) have been selected. Only 1290 of these wells have a public-available composite log and fit with the basic prerequisites for CO2 storage potential, mostly as deep saline aquifer/s presence. Wells data have been organized into a geodatabase containing information about the nature and the thickness of geological formations, the presence of fresh, saline or brackish water, brine, gas and oil, the underground temperature, the permeability, porosity and geochemical characteristics of the caprock and the reservoirs lithologies. Available maps, seismic and geological profiles containing or closer to the analyzed wells have been catalogued too. In order to constrain the supercritical behaviour of the CO2 and to prevent the escape of gaseous CO2 to the surface, a first evaluation of the caprock presence and quality has been done on these selected wells. Using a numerical parameterization of the caprock lithologies, a “Caprock Quality Factor” (Fbp) has been defined, which clustered the wells into 5 different classes of caprock impermeability (ranging between the lowest 1 to highest 5). The analysis shows that more than 50% of the selected wells have an Fbp Factor between 4 and 5 (good and optimal quality of caprock), and are mostly located in foredeep basins of the Alps-Apenninic Chain. The geodatabase also includes: i) the seismogenetic sources (INGV DISS 3.0.4 Database of Individual Seismogenetic Sources), ii) an elaboration of seismic events catalogues (INGV CFTI, CPTI04, NT4.1), iii) the Diffuse Degassing Structures (DDS), as part of the INGV project V5 diffuse degassing in Italy geodatabase, considered as “CO2 analogue” field-tests, iv) the distribution of the thermal anomalies on the Italian Territory, linked to the presence of volcanic CO2 emissions, in order to consider the CO2 diffuse degassing risk assessment on the Italian territory Successively it has been created a geodatabase on the nature and quality of deep aquifers for the high-ranking wells sub-dataset (where the aquifers data are available), containing the following parameters: i) presence of one or more aquifers deeper than 800 meters; ii) thickness of the aquifer/s; iii) lithology of the reservoir/s; iv) available chemical analysis; v) distance from closer power plants or other anthropogenic CO2 sources.The final aim of these work is to help to find potential areas in Italy where CO2 storage feasibility studies can be done. In these cases it is necessary to implement the knowledge by: i) better evaluation of saline aquifer quality; ii) estimation of CO2 storage capacity by 3D-modeling of deep crustal structures; iii) fluid-dynamic and geochemical modelling of water-rock-CO2 interaction paths.