Extensional shear zones as imaged by reflection seismic lines: the Larderello geothermal field (central Italy)

Brogi, Andrea; Lazzarotto, A.; Liotta, Domenico; Ranalli, Giorgio

doi:10.1016/s0040-1951(02)00668-6

Cited by 85 publications

(65 citation statements)

References 23 publications

(22 reference statements)

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“…The BDT in the earth is generally viewed as a transition between two different constitutive behaviors, viscoelastic and plastic (Dragoni, 1990). There is evidence that the K horizon in the upper crust of central Italy corresponds to a shear plane separating the brittle crust from the ductile crust (Brogi et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

Simulation of seismic waves at the earth's crust (brittle–ductile transition) based on the Burgers model

et al. 2014

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Abstract. The earth's crust presents two dissimilar rheological behaviors depending on the in situ stress-temperature conditions. The upper, cooler part is brittle, while deeper zones are ductile. Seismic waves may reveal the presence of the transition but a proper characterization is required. We first obtain a stress-strain relation, including the effects of shear seismic attenuation and ductility due to shear deformations and plastic flow. The anelastic behavior is based on the Burgers mechanical model to describe the effects of seismic attenuation and steady-state creep flow. The shear Lamé constant of the brittle and ductile media depends on the in situ stress and temperature through the shear viscosity, which is obtained by the Arrhenius equation and the octahedral stress criterion. The P and S wave velocities decrease as depth and temperature increase due to the geothermal gradient, an effect which is more pronounced for shear waves. We then obtain the P -S and SH equations of motion recast in the velocity-stress formulation, including memory variables to avoid the computation of time convolutions. The equations correspond to isotropic anelastic and inhomogeneous media and are solved by a direct grid method based on the Runge-Kutta time stepping technique and the Fourier pseudospectral method. The algorithm is tested with success against known analytical solutions for different shear viscosities. A realistic example illustrates the computation of surface and reverse-VSP synthetic seismograms in the presence of an abrupt brittle-ductile transition.

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Section: Introductionmentioning

confidence: 99%

Simulation of seismic waves at the earth's crust (brittle–ductile transition) based on the Burgers model

et al. 2014

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“…The complex geologic and tectonic settings of this area have been studied by several authors ( [51][52][53][54] and references therein).…”

Section: Regional Geological Settingmentioning

confidence: 99%

Modeling Highly Buoyant Flows in the Castel Giorgio: Torre Alfina Deep Geothermal Reservoir

et al. 2018

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The Castel Giorgio-Torre Alfina (CG-TA, central Italy) is a geothermal reservoir whose fluids are hosted in a carbonate formation at temperatures ranging between 120 ∘ C and 210 ∘ C. Data from deep wells suggest the existence of convective flow. We present the 3D numerical model of the CG-TA to simulate the undisturbed natural geothermal field and investigate the impacts of the exploitation process. The open source finite-element code OpenGeoSys is applied to solve the coupled systems of partial differential equations. The commercial software FEFLOW5 is also used as additional numerical constraint. Calculated pressure and temperature have been calibrated against data from geothermal wells. The flow field displays multicellular convective patterns that cover the entire geothermal reservoir. The resulting thermal plumes protrude vertically over 3 km at Darcy velocity of about 7 * 10 −8 m/s. The analysis of the exploitation process demonstrated the sustainability of a geothermal doublet for the development of a 5 MW pilot plant. The buoyant circulation within the geothermal system allows the reservoir to sustain a 50-year production at a flow rate of 1050 t/h. The distance of 2 km, between the production and reinjection wells, is sufficient to prevent any thermal breakthrough within the estimated operational lifetime. OGS and FELFOW results are qualitatively very similar with differences in peak velocities and temperatures. The case study provides valuable guidelines for future exploitation of the CG-TA deep geothermal reservoir. IntroductionSince the 1970s, the increasing threat of a worldwide energy crisis has prompted many governments to reduce their dependence on traditional nonrenewable energy sources focusing on renewable ones (e.g., geothermal energy, hydroelectric, wind-energy, and several forms of solar energy, such as bioenergy, biofuel, photovoltaic, and solar-thermal energy [1]). Geothermal energy is expected to play an increasing role to meet future power demand. This is related to its enormous exploiting potential, which is capturing the attention of industries also due to technological advances in the exploration of promising geothermal fields [2,3].Most of the world famous geothermal energy sources exploited today are associated with volcanic and/or recent tectonically active areas. Important examples are the geothermal areas of Yellowstone [4][5][6] northern California [7], the Pannonic Basin [8], and the Rhine Graben [9][10][11]. Italy strongly contributes to the development of geothermal power generation. In 1904, the world first electrical power was produced from a geothermal energy source in the Larderello site (Tuscany, central Italy) [1,[12][13][14][15][16][17][18].Beyond the world famous Larderello system, fossil and active hydrothermal manifestations are distributed all along the Preappennine belt of central Italy, facing the Tyrrhenian coast. This area has undergone both lithospheric extension and upper mantle doming. Such processes have been active since the Miocene [19,20] and are likely...

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“…From the Middle Miocene, the structural stacking was affected by extensional processes, related to the development of the Tyrrhenian Sea [19][20][21]. Such processes generated Plio-Pleistocene basins, interpreted by many authors as controlled by longitudinal systems of high angle normal faults, assuming a continuous extensional regime from the Middle Miocene to the Present [21][22][23]. The tectonic depressions of the Neogene Basins have been so affected by a deposition of continental and marine sediments (Neogene-Quaternary age).…”

Section: Climate Geology and Hydrogeologymentioning

confidence: 99%

“…For the springs (3, 4, 4bis, 21, 44, 47) and wells (11,12,23,27,29) that drain groundwater from sandstones in the Scansano-Pancole zone, a recharge average altitude in the range 600-700 m (a.s.l.) is assessable.…”

mentioning

confidence: 99%

Water Isotopes as Environmental Tracers for Conceptual Understanding of Groundwater Flow: An Application for Fractured Aquifer Systems in the “Scansano-Magliano in Toscana” Area (Southern Tuscany, Italy)

Doveri

Mussi

2014

Water

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Abstract:The "Scansano-Magliano in Toscana" area is characterized by a morpho-structure chiefly made-up by sandstone and shelly-calcareous lithologies. Generally, these complexes host minor aquifers in Tuscany, since they have medium to medium-low permeability. In the area under examination, a sandstone outcrop develops with continuity along the ridge of the structure for several kilometers and above a shelly substratum. Consequently, this hydrostructural context suggested the possibility that a significant groundwater body was hosted in the sandstones. In order to verify this assumption, an isotopic study was carried out taking into account several wells and springs sited on the sandstone outcrop and its surrounding area; the samples collected over a period of two years were analyzed to obtain δ 18 O‰, δ 2 H‰ and 3 H. A study of the hydrostructural and morphological condition was also performed, and minor springs were selected. The analyses of this spring-water resulted in the characterization of the isotopic features of the infiltration water in the studied area, which represents a fundamental base of work for the interpretation of the data of groundwater points which drain long flow paths. By means of this approach, the groundwater framework was defined and the presence of a significant and continuous groundwater body within the sandstone complex was verified. A preliminary conceptual hydrogeological model was also proposed.

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Extensional shear zones as imaged by reflection seismic lines: the Larderello geothermal field (central Italy)

Cited by 85 publications

References 23 publications

Simulation of seismic waves at the earth's crust (brittle–ductile transition) based on the Burgers model

Simulation of seismic waves at the earth's crust (brittle–ductile transition) based on the Burgers model

Modeling Highly Buoyant Flows in the Castel Giorgio: Torre Alfina Deep Geothermal Reservoir

Water Isotopes as Environmental Tracers for Conceptual Understanding of Groundwater Flow: An Application for Fractured Aquifer Systems in the “Scansano-Magliano in Toscana” Area (Southern Tuscany, Italy)

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