Sample records for piezometry
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Brandstätter, Jennifer; Kurz, Walter; Rogowitz, Anna
2017-08-01
In this study we present microstructural data from hydrothermal veins in the sedimentary cover and the igneous basement recovered from Hole U1414A, Integrated Ocean Drilling Program (IODP) Expedition 344 (Costa Rica Seismogenesis Project), to constrain deformation mechanism operating in the subducting Cocos Plate. Cathodoluminescence studies, mechanical e-twin piezometry and electron backscatter diffraction (EBSD) analyses of carbonate veins were used to give insights into the deformation conditions and to help to understand the tectonic deformation history of the Cocos Plate offshore Costa Rica. Analyses of microstructures in the sedimentary rocks and in the basalt of the igneous basement reveal brittle deformation, as well as crystal-plastic deformation of the host rock and the vein material. Cathodoluminescence images showed that in the basalt fluid flow and related precipitation occurred over several episodes. The differential stresses, obtained from two different piezometers using the same parameter (twin density), indicate various mean differential stresses of 49 ± 11 and 69 ± 30 MPa and EBSD mapping of calcite veins reveals low-angle subgrain boundaries. Deformation temperatures are restricted to the range from 170°C to 220°C, due to the characteristics of the existing twins and the lack of high-temperature intracrystalline deformation mechanisms (>220°C). The obtained results suggest that deformation occurred over a period associated with changes of ambient temperatures, occurrence of fluids and hydrofracturing, induced differential stresses due to the bending of the plate at the trench, and related seismic activity.
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Van der Werf, Thomas F.; Chatzaras, Vasileios; Tikoff, Basil; Drury, Martyn R.
2016-04-01
Baja California is an active transtensional rift zone, which links the San Andreas Fault with the East Pacific Rise. The erupted basalts of the Holocene San Quintin volcanic field contain xenoliths, which sample the lower crust and upper mantle beneath Baja California. The aim of this research is to gain insight in the rheology of the lower crust and the upper mantle by investigating the xenolith microstructure. Microstructural observations have been used to determine the dominant deformation mechanisms. Differential stresses were estimated from recrystallized grain size piezometry of plagioclase and clinopyroxene for the lower crust and olivine for the upper mantle. The degree of deformation can be inferred from macroscopic foliations and the deformation microstructures. Preliminary results show that both the lower crust and the upper mantle have been affected by multiple stages of deformation and recrystallization. In addition the dominant deformation mechanism in both the lower crust and the upper mantle is dislocation creep based on the existence of strong crystallographic preferred orientations. The differential stress estimates for the lower crust are 10-29 MPa using plagioclase piezometry and 12-35 MPa using clinopyroxene piezometry. For the upper mantle, differential stress estimates are 10-20 MPa. These results indicate that the strength of the lower crust and the upper mantle are very similar. Our data do not fit with the general models of lithospheric strength and may have important implications for the rheological structure of the lithosphere in transtensional plate margins and for geodynamic models of the region.
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International Nuclear Information System (INIS)
2011-01-01
The authors report the updating of the non-saturated area (ZNS), and therefore of the vulnerability, by means of a recent improvement of knowledge of alluvial sheet piezometry in the south of the Tricastin nuclear power plant site, and the harmonization of this locally updated map with previous versions of the vulnerability map (2007 and 2009), in order to produce an updated vulnerability map for an area of 60 km around the Tricastin nuclear power plant. Thus, they firstly report the updating of the thickness grid of non saturated area by means of a processing of the piezometric map, and secondly a calculation of the simplified vulnerability
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Manteca, Ivan Alhama
The Agua Amarga coastal aquifer, located in the south of Alicante province, has been subjected to successive anthropogenic actions: salt works activity (1925-1975) and water withdrawal to supply the Alicante I and II desalination plants (since 2003). These interventions have influenced the salinity and the flow regime. Due to the existence of a salt marsh of ecological interest linked to the aquifer, the 'Mancomunidad de los Canales del Taibilla' (agency responsible for the desalination plants) designed a piezometric network for monitoring piezometry and electrical conductivity (in operation since May 2008). Soil humidity and piezometrics levels have been recovered by means of a seawater pouring programme over the salt marsh (since December 2009),which represents the third anthropic intervention. In this memoria, we investigate the Agua Amarga coastal aquifer to develop a physical conceptual model. Firstly, the study area is characterized in relation to climatology, geology, geomorphology and hydrogeology, using published information, describing, in addition, the desalination plants catchment system. Next, based on hydrogeological studies prior to the start up of the desalination plants, the aquifer is characterized: type, lithology, hydraulic parameters, thickness, surface extension, etc. Water quantity relating to rainfall, water withdrawal and pourings over the salt marsh, have been integrated in conjunction with data from monthly piezometric campaigns. In adittion, in order to gain insight into the groundwater mixing processes, chemical and isotope analyses were carried out on meteoric water and groundwater samples taken at different locations. The results were used to elaborate a conceptual physical model and a water budget. As an extension tool to understand processes and assess aquifer management, a 3-D fluid-flow and solute-transport model is designed with SEAWAT. Also, the 2-D physical characterization of scenarios with seawater intrusion and salt flats is
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Khomsi, Sami; Echihi, Oussema; Slimani, Naji
2012-03-01
A set of different data including high resolution seismic sections, petroleum wire-logging well data, borehole piezometry, structural cross-sections and outcrop analysis allowed us to characterise the tectonic framework, and its relationships with the deep aquifers seated in Cretaceous-Miocene deep reservoirs. The structural framework, based on major structures, controls the occurrence of deep aquifers and sub-basin aquifer distributions. Five structural domains can be defined, having different morphostructural characteristics. The northernmost domain lying on the north-south axis and Zaghouan thrust system is a domain of recharge by underflow of the different subsurface reservoirs and aquifers from outcrops of highly fractured reservoirs. On the other hand, the morphostructural configuration controls the piezometry of underground flows in the Plio-Quaternary unconfined aquifer. In the subsurface the Late Cretaceous-Miocene reservoirs are widespread with high thicknesses in many places and high porosities and connectivities especially along major fault corridors and on the crestal parts of major anticlines. Among all reservoirs, the Oligo-Miocene, detritic series are widespread and present high cumulative thicknesses. Subsurface and fieldwork outline the occurrence of 10 fractured sandy reservoirs for these series with packages having high hydrodynamic and petrophysical characteristics. These series show low salinities (maximum 5 g/l) in the northern part of the study area and will constitute an important source of drinkable water for the next generations. A regional structural cross-section is presented, compiled from all the different data sets, allowing us to define the major characteristics of the hydrogeological-hydrogeothermal sub-basins. Eight hydrogeological provinces are defined from north-west to south-east. A major thermal anomaly is clearly identified in the south-eastern part of the study area in Sfax-Sidi Il Itayem. This anomaly is possibly related to
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Neves, Maria C.; Costa, Luis; Monteiro, José P.
2016-06-01
Karst aquifers in semi-arid regions, like Querença-Silves (Portugal), are particularly vulnerable to climate variability. For the first time in this region, the temporal structure of a groundwater-level time series (1985-2010) was explored using the continuous wavelet transform. The investigation focused on a set of four piezometers, two at each side of the S. Marcos-Quarteira fault, to demonstrate how each of the two sectors of the aquifer respond to climate-induced patterns. Singular spectral analysis applied to an extended set of piezometers enabled identification of several quasi-periodic modes of variability, with periods of 6.5, 4.3, 3.2 and 2.6 years, which can be explained by low-frequency climate patterns. The geologic forcing accounts for ~15 % of the differential variability between the eastern and western sectors of the aquifer. The western sector displays spatially homogenous piezometric variations, large memory effects and low-pass filtering characteristics, which are consistent with relatively large and uniform values of water storage capacity and transmissivity properties. In this sector, the 6.5-year mode of variability accounts for ~70 % of the total variance of the groundwater levels. The eastern sector shows larger spatial and temporal heterogeneity, is more reactive to short-term variations, and is less influenced by the low-frequency components related to climate patterns.
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Hydrogeological functioning of the tablecloth of the Midelt Furrow (High Moulouya, MOROCCO)
Ikhmerdi, H.; Boukdir, A.; Kossir, A.; Alili, L.; Ben-Said, E.
2018-05-01
The superficial tablecloth of furrow of Midelt belongs to the bowl of High Moulouya which stretches out from the west eastward between the High Atlas in the South and the Medium Atlas west and in the Northeast. The methodology used includes the synthesis of geological data, piezometry, hydrodynamics, hydroclimatology and water quality. This study provides the following results: The flow mode of the water table is general SW to NE on the left bank of the Moulouya river and on the right bank, the flow is from the NW to the SE. The piezometric ratings vary from 1460 to 1780 m. The hydraulic gradient is the order of 2% on average. The transmissivity is usually about 10-3 m2/s. the punctual flows can reach 50 l / s (case of the drilling N ° IRE 879/38 realized in the alluviums of the Outat). The flow provided by the sources from conglomerates and lake limestones of the Plio-Villafranchien is 50 l / s. The unit of the Mio- Plio-Quaternary aquifer is fed from the infiltrations of rains, by the wadis which cross the banks of the conglomerates and by the landing of the tablecloths of Lias, Dogger and Cretaceous this feeding is however weak in because of the discontinuity of the formations and the poor permeability of the different levels. From a qualitative point of view the groundwater analysis of the aquifer shows that their overall quality is average to good.
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International Nuclear Information System (INIS)
Karima, Boukhari; Sadik, Er-Rouane; Abdeljalil, Gouzrou
2004-01-01
The field of study includes the plain of Mejjate and its Western termination, located at 70km in the Western South of Marrakech, on a surface of 2800 km 2 , delimited in North by the links of Jbilet, in the South by the High Western Atlas, in the East by wadi N'Fis and the West by the large basin of Essaouira-Meskala. The principal rural agglomerations are Imintanout, Chichaoua, Sebt Mzouda, Had Mejjate, Guemassa, Zaouiet Sidi Abdelmoumen Taouloukt and Bouabout. The principal socioeconomic activity is the breeding and the cereal farming in bour, the total surface irrigated in all the area is about 7500 ha. Precipitations have a continental mode of and type to semi-arid, characterized by an absence of the rains in the duration and summer months and rains brutal short to the remainder of the year. The annual average temperatures vary from 12 with 28 o C, with an annual average of 19.32 o C. The principal objective of this study consists in studying the impact of the dryness on the hydrous potentialities of the area of study. In this approach, one studied the variations in the course of the time of several components to know precipitations, the flows of the w adis a nd the sources and the piezometry of the Plio-quaternary tablecloth. Within the same framework and for better judging the relation, which exists between these arious components, one tried to carry out tests of linear correlation to examine whether there is a statistical bond between them.(Author)
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Stewart, Craig A.; Miranda, Elena A.
2017-12-01
We investigate how the rheological evolution of shear zone rocks from beneath the brittle-ductile transition (BDT) is affected by coeval ductile shear and pseudotachylyte development associated with seismicity during the earthquake cycle. We focus our study on footwall rocks of the South Mountains core complex, and we use electron backscatter diffraction (EBSD) analyses to examine how strain is localized in granodiorite mylonites both prior to and during pseudotachylyte development beneath the BDT. In mylonites that are host to pseudotachylytes, deformation is partitioned into quartz, where quartz exhibits crystallographic-preferred orientation patterns and microstructures indicative of dynamic recrystallization during dislocation creep. Grain size reduction during dynamic recrystallization led to the onset of grain boundary sliding (GBS) accommodated by fluid-assisted grain size-sensitive (GSS) creep, localizing strain in quartz-rich layers prior to pseudotachylyte development. The foliation-parallel zones of GBS in the host mylonites, and the presence of GBS traits in polycrystalline quartz survivor clasts indicate that GBS zones were the ductile precursors to in situ pseudotachylyte generation. During pseudotachylyte development, strain was partitioned into the melt phase, and GSS deformation in the survivor clasts continued until crystallization of melt impeded flow, inducing pseudotachylyte development in other GBS zones. We interpret the coeval pseudotachylytes with ductile precursors as evidence of seismic events near the BDT. Grain size piezometry yields high differential stresses in both host mylonites ( 160 MPa) and pseudotachylyte survivor clasts (> 200 MPa), consistent with high stresses during interseismic and coseismic phases of the earthquake cycle, respectively.
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International Nuclear Information System (INIS)
Bórnez Mejías, K.; Mejías Moreno, M.; Camuñas Palencia, C.; Pozo Tejado, J. del; Moral Fernández del Rincón, A. del
2017-01-01
This paper presents one of the first detailed studies about the ground collapses that have taken place in recent years in the central area of the groundwater body of the Western Mancha I, in the province of Ciudad Real. The main source of the collapses is the breakdowns of the roof of the karst cavities, as a result of a rapid and unusual increase in the groundwater, due to the despread and intense rainfall, such as those that took place in the wet period (2009-2013). This brought about a washing of the karstic system, the movement of water through sinks and preferential channels, which had been dry for decades, as well as dissolution of the chalky material itself. This ascent phase of the groundwater was preceded by a steady decrease in the piezometric levels, caused by prolonged drought and over-exploitation through pumping. To obtain an optimum knowledge of the area of study, important research has been done to localize, measure and classify each of the collapses. Along with this, we have compiled, expanded and updated the data of the piezometry, to a high level of detail. We have been able to distinguish four types of ground collapses: alluvial collapses, collapses in areas of dolines, lagoon collapses and of intermediate types of collapses. It is also evident that with the passage of years, the collapses that have been produced are of lesser dimensions. Finally, we have deduced the areas which have a greater susceptibility for new collapses, in places such as the river Guadiana, the lagoon areas, and some areas of dolines. [es
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Lachaal, Fethi; Bédir, Mourad; Tarhouni, Jamila; Gacha, Ayadi Ben; Leduc, Christian
2011-06-01
The Zéramdine and Mahdia-Jébéniana blocks are located in the Sahel region in east-central Tunisia. Active tectonics have divided the region into numerous sub-units, as result of multiple phases of distension and compression. The Miocene fluvio-deltaic sediment sandy layers have aquiferous capacities but their hydraulic properties are still unknown, due to the lack of investigation wells. This study proposes a new description of the regional hydrogeology of Miocene deposits. Seismic-reflection and wireline logging of petroleum and water wells were used to understand the structure and the geometry of the Miocene reservoirs. The groundwater flow and its relationship to the sedimentary and tectonic context were then identified by studying piezometry and hydrochemistry. Two Miocene deep aquifer systems were identified: (1) Zéramdine-Béni Hassen to the north and (2) Jébéniana-Ksour Essef to the south. These aquifers are separated by the Mahdia graben. Other major tectonic structures, such as the Zéramdine fault corridor, the Moknine graben, and the El-Jem half-graben represent lateral boundaries for these aquifers. Other deeper sandy and clayey-sandy reservoirs were also identified in the area. Their repartition, thickness and depth vary from one block to other. Hydrodynamics of the deep aquifers seems to be controlled by geological structures. Two independent compartments were identified: in the northern block groundwater flows from West to East and from Northwest to Southeast, while in the southern block it flows from Northwest to Southeast. Geochemical facies are of two types: Na-Ca-Cl-SO 4 for the Zéramdine-Béni Hassen deep aquifer and Na-Cl for the Jébéniana-Ksour Essef deep aquifer. The hydrodynamic and geochemical results confirm the sharing of the Miocene sediments into two aquifers.
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Energy Technology Data Exchange (ETDEWEB)
Silva, Jose Roberto de Alcantara e
2003-07-01
This work analyzes the geological-geotechnical-geophysical behavior, aiming to define the characteristics of a karstic-fissural aquifer in the mid-northern region of the State of Ceara, named as Itataia Phosphor-Uranium Deposit. This area is constituted of marbles and gneisses from Itataia Group, which are morphologically located at a higher point to the south and at a lower point to the north, related to Paleoproterozoic Era. Fracture system led to the implantation of two karstic marble phases, being the oldest from Cambrian Period and the most recent from Tertiary/Quaternary Period. Porosity is secondary to fractures, fissures and crushed zones which act as hydraulic channels for groundwater flow. Major geophysics defined conducting lines are controlled by normal fractures and faults in both N70 deg E and N80 deg W directions, and secondarily in both N10 deg E and N30 deg W directions, dipping 70 deg -85 deg into the northern quadrant of the main axes. Fault characteristics are typical of graben and horst patterns. Rocks in the area are distributed into three classes of geotechnical massif: healthy rock, moderately altered and fractured rock, and strongly altered and fractured rock. The latter occurs predominantly in the center of the area, from the soil surface to an average depth of 150 meters. Groundwater flow is characterized by fractures which enlarged by the karstic phenomenon dissolution, and then become closer as deeper they are. This flow may be slower or even discontinue in light of silty-argillaceous alteration material that fill the open fracture gaps. Water level is not lower than 5 m or higher than 90 m, averaging by 30 m ali over the area. The synoptic piezometry map shows a general south-north direction; however in the southwestern portion - the recharge zone - it takes the south direction, while in the southeastern portion it takes the southeast direction. (author)
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Hydrogeological characterization of Itataia mine, Ceara, Brazil
International Nuclear Information System (INIS)
Silva, Jose Roberto de Alcantara e
2003-01-01
This work analyzes the geological-geotechnical-geophysical behavior, aiming to define the characteristics of a karstic-fissural aquifer in the mid-northern region of the State of Ceara, named as Itataia Phosphor-Uranium Deposit. This area is constituted of marbles and gneisses from Itataia Group, which are morphologically located at a higher point to the south and at a lower point to the north, related to Paleoproterozoic Era. Fracture system led to the implantation of two karstic marble phases, being the oldest from Cambrian Period and the most recent from Tertiary/Quaternary Period. Porosity is secondary to fractures, fissures and crushed zones which act as hydraulic channels for groundwater flow. Major geophysics defined conducting lines are controlled by normal fractures and faults in both N70 deg E and N80 deg W directions, and secondarily in both N10 deg E and N30 deg W directions, dipping 70 deg -85 deg into the northern quadrant of the main axes. Fault characteristics are typical of graben and horst patterns. Rocks in the area are distributed into three classes of geotechnical massif: healthy rock, moderately altered and fractured rock, and strongly altered and fractured rock. The latter occurs predominantly in the center of the area, from the soil surface to an average depth of 150 meters. Groundwater flow is characterized by fractures which enlarged by the karstic phenomenon dissolution, and then become closer as deeper they are. This flow may be slower or even discontinue in light of silty-argillaceous alteration material that fill the open fracture gaps. Water level is not lower than 5 m or higher than 90 m, averaging by 30 m ali over the area. The synoptic piezometry map shows a general south-north direction; however in the southwestern portion - the recharge zone - it takes the south direction, while in the southeastern portion it takes the southeast direction. (author)
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Cawood, T. K.; Platt, J. P.
2017-12-01
A widely-accepted model for the rheology of crustal-scale shear zones states that they comprise distributed strain at depth, in wide, high-temperature shear zones, which narrow to more localized, high-strain zones at lower temperature and shallower crustal levels. We test and quantify this model by investigating how the width, stress, temperature and deformation mechanisms change with depth in the Simplon Shear Zone (SSZ). The SSZ marks a major tectonic boundary in the central Alps, where normal-sense motion and rapid exhumation of the footwall have preserved evidence of older, deeper deformation in rocks progressively further into the currently-exposed footwall. As such, microstructures further from the brittle fault (which represents the most localized, most recently-active part of the SSZ) represent earlier, higher- temperature deformation from deeper crustal levels, while rocks closer to the fault have been overprinted by successively later, cooler deformation at shallower depths. This study uses field mapping and microstructural studies to identify zones representing deformation at various crustal levels, and characterize each in terms of zone width (representing width of the shear zone at that time and depth) and dominant deformation mechanism. In addition, quartz- (by Electron Backscatter Diffraction, EBSD) and feldspar grain size (measured optically) piezometry are used to calculate the flow stress for each zone, while the Ti-in-quartz thermometer (TitaniQ) is used to calculate the corresponding temperature of deformation. We document the presence of a broad zone in which quartz is recrystallized by the Grain Boundary Migration (GBM) mechanism and feldspar by Subgrain Rotation (SGR), which represents the broad, deep zone of deformation occurring at relatively high temperatures and low stresses. In map view, this transitions to successively narrower zones, respectively characterized by quartz SGR and feldspar Bulge Nucleation (BLG); quartz BLG and brittle
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Energy Technology Data Exchange (ETDEWEB)
Zarlenga, Francesco; Basili, Mauro; Del Ciello, Roberto [ENEA, Centro Ricerche Casaccia, Rome (Italy). Dipt. Ambiente
1997-10-01
The most important aspects of environmental geology, related to the urban syatems are analysed in this paper; the term urban system is here preferred to urban environment, since the second one refers to a part of a complex system, that comprises social, economic, etc. environments. All the possible environmental impacts have been described to evaluate how the urban system is affected by the environmental geological components. They are subdivided into urban impacts on the environment and environmental impacts on the cities. The environmental changes induced by: quarries, natural surfaces waterproofing, drained marshes, subways for transportation networks, bridges and gully-holes, topography changes, natural hollows filling up and ground piles, loss of the natural conditions for river beds, loss of soils, falls in piezometry and connected subsistence phenomena, are classified into the firdt type of impacts, also defined as anthropic risks. The pollution of soils, surface waters (marine and fluvial), groundwater and the impact of watse management and their restorage were also dealth with. The geological risks have also been analyzed as pressure factors from the environmenton the cities. They are generally interrelated and in some cases added up. The main instruments to help monitor and manage the environment are also described. They are monitoring networks that constitute a part of the Informative Environmental Systems. A great relevance is given to the indicators and indexes of the environmental quality, either for the measurement of the quality of life that for the measurement of environmental sustainability of cities. The scientific use of such indicators and indexes is presently a subject of debate world-wide. The authors consider is correct to delineate concise indexes, obtained from state indicators for the quality of life. They are represented by the umber of days/per year in which a service was suspended, or the environment didn`t present the characteristics
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Energy Technology Data Exchange (ETDEWEB)
Bórnez Mejías, K.; Mejías Moreno, M.; Camuñas Palencia, C.; Pozo Tejado, J. del; Moral Fernández del Rincón, A. del
2017-09-01
This paper presents one of the first detailed studies about the ground collapses that have taken place in recent years in the central area of the groundwater body of the Western Mancha I, in the province of Ciudad Real. The main source of the collapses is the breakdowns of the roof of the karst cavities, as a result of a rapid and unusual increase in the groundwater, due to the despread and intense rainfall, such as those that took place in the wet period (2009-2013). This brought about a washing of the karstic system, the movement of water through sinks and preferential channels, which had been dry for decades, as well as dissolution of the chalky material itself. This ascent phase of the groundwater was preceded by a steady decrease in the piezometric levels, caused by prolonged drought and over-exploitation through pumping. To obtain an optimum knowledge of the area of study, important research has been done to localize, measure and classify each of the collapses. Along with this, we have compiled, expanded and updated the data of the piezometry, to a high level of detail. We have been able to distinguish four types of ground collapses: alluvial collapses, collapses in areas of dolines, lagoon collapses and of intermediate types of collapses. It is also evident that with the passage of years, the collapses that have been produced are of lesser dimensions. Finally, we have deduced the areas which have a greater susceptibility for new collapses, in places such as the river Guadiana, the lagoon areas, and some areas of dolines. [Spanish] This paper presents one of the first detailed studies about the ground collapses that have taken place in recent years in the central area of the groundwater body of the Western Mancha I, in the province of Ciudad Real. The main source of the collapses is the breakdowns of the roof of the karst cavities, as a result of a rapid and unusual increase in the groundwater, due to the widespread and intense rainfall, such as those that
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Rheological structure of the lithosphere in plate boundary strike-slip fault zones
Chatzaras, Vasileios; Tikoff, Basil; Kruckenberg, Seth C.; Newman, Julie; Titus, Sarah J.; Withers, Anthony C.; Drury, Martyn R.
2016-04-01
How well constrained is the rheological structure of the lithosphere in plate boundary strike-slip fault systems? Further, how do lithospheric layers, with rheologically distinct behaviors, interact within the strike-slip fault zones? To address these questions, we present rheological observations from the mantle sections of two lithospheric-scale, strike-slip fault zones. Xenoliths from ˜40 km depth (970-1100 ° C) beneath the San Andreas fault system (SAF) provide critical constraints on the mechanical stratification of the lithosphere in this continental transform fault. Samples from the Bogota Peninsula shear zone (BPSZ, New Caledonia), which is an exhumed oceanic transform fault, provide insights on lateral variations in mantle strength and viscosity across the fault zone at a depth corresponding to deformation temperatures of ˜900 ° C. Olivine recrystallized grain size piezometry suggests that the shear stress in the SAF upper mantle is 5-9 MPa and in the BPSZ is 4-10 MPa. Thus, the mantle strength in both fault zones is comparable to the crustal strength (˜10 MPa) of seismogenic strike-slip faults in the SAF system. Across the BPSZ, shear stress increases from 4 MPa in the surrounding rocks to 10 MPa in the mylonites, which comprise the core of the shear zone. Further, the BPSZ is characterized by at least one order of magnitude difference in the viscosity between the mylonites (1018 Paṡs) and the surrounding rocks (1019 Paṡs). Mantle viscosity in both the BPSZ mylonites and the SAF (7.0ṡ1018-3.1ṡ1020 Paṡs) is relatively low. To explain our observations from these two strike-slip fault zones, we propose the "lithospheric feedback" model in which the upper crust and lithospheric mantle act together as an integrated system. Mantle flow controls displacement and the upper crust controls the stress magnitude in the system. Our stress data combined with data that are now available for the middle and lower crustal sections of other transcurrent fault
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Selected topics of fluid mechanics
Kindsvater, Carl E.
1958-01-01
The fundamental equations of fluid mechanics are specific expressions of the principles of motion which are ascribed to Isaac Newton. Thus, the equations which form the framework of applied fluid mechanics or hydraulics are, in addition to the equation of continuity, the Newtonian equations of energy and momentum. These basic relationships are also the foundations of river hydraulics. The fundamental equations are developed in this report with sufficient rigor to support critical examinations of their applicability to most problems met by hydraulic engineers of the Water Resources Division of the United States Geological Survey. Physical concepts are emphasized, and mathematical procedures are the simplest consistent with the specific requirements of the derivations. In lieu of numerical examples, analogies, and alternative procedures, this treatment stresses a brief methodical exposition of the essential principles. An important objective of this report is to prepare the user to read the literature of the science. Thus, it begins With a basic vocabulary of technical symbols, terms, and concepts. Throughout, emphasis is placed on the language of modern fluid mechanics as it pertains to hydraulic engineering. The basic differential and integral equations of simple fluid motion are derived, and these equations are, in turn, used to describe the essential characteristics of hydrostatics and piezometry. The one-dimensional equations of continuity and motion are defined and are used to derive the general discharge equation. The flow net is described as a means of demonstrating significant characteristics of two-dimensional irrotational flow patterns. A typical flow net is examined in detail. The influence of fluid viscosity is described as an obstacle to the derivation of general, integral equations of motion. It is observed that the part played by viscosity is one which is usually dependent on experimental evaluation. It follows that the dimensionless ratios known as
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Isotopes to Study the coastal aquifer plain, Cap Bon, Tunisia
International Nuclear Information System (INIS)
Ben Hamouda, M. F.; Zouari, Kamel; Tarhouni, J.; Gaye, C.B.; Oueslati, M.N.
2005-01-01
some sites the presence of bomb-tritium indicates a modern component of recharge in the groundwater. This suggests that the aquifer is unconfined, at least in its upper layer. 14C data will be used to estimate the rate of local recharge. The salinity of the groundwater appears to originate from dissolution of minerals (halite) in the aquifer system. The higher values of the dissolved anions and cations in korba area are due to higher sodium and chloride concentrations coming from mixture with sea water. The changes of the latter concentration seem to be associated with changes of the proportion of local recharge. In general, the oriental coast aquifer system receives relatively a good recharge coming from water of current precipitation. This contribution of current water is shown also on the deep aquifer, in particular on the level of the piedmont. This situation seems to indicate that the reconstitution of the reserves is fast in these areas. The salinity is generally acquired by dissolution associated with a process of evaporation.However for the shallow aquifer a contamination by a mixture with seawater is extremely probable, in particular in the sectors of Korba and Tefelloune, where we observe a negative piezometry and the salinity can reach the 8 g/l
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Regional modelling of the confined aquifers below the Boom clay in NE-Belgium
International Nuclear Information System (INIS)
Vandersteen, K.; Gedeon, M.; Marivoet, J.; Wouters, L.
2012-01-01
- Paniselian-Brusselian aquifer and the Boom Clay confining the Oligocene aquifer system. The northern and western boundaries of the model are chosen arbitrarily and go towards the north nearly as far as the Oosterschelde River and towards the west as far as Zeeland. The eastern boundary is placed at the fault system of the Roer Valley Graben in the northeast of the Campine. Groundwater pumping is the most important process that affects the groundwater flow in the deep aquifer system. Therefore, we reconstructed the pumping history in the Oligocene aquifer, the Bartoon aquitard system and the Ledo-Paniselian-Brusselian aquifer as far as possible into the past. The year 1950 was chosen as starting date for the transient simulation, mainly because legislation concerning the use of groundwater and its registration goes back until 1946. The analysis of the piezometry of the confined deep aquifer system allowed gaining more insight in the evolution of the piezometric heads caused by intensive pumping. Since the Oligocene aquifer has a significantly lower permeability compared to the Ledo-Paniselian-Brusselian aquifer, the Oligocene pumping triggers only local effects on groundwater levels. Hence, the regional effects in the Oligocene aquifer are presumably caused by pumping in the Ledo-Paniselian-Brusselian aquifer, whereby the hydraulically isolating Maldegem Formation dampens these effects. The amount of this dampening is given by the spatial distribution of the hydraulic properties of the Maldegem Formation and/or its variable thickness. For the piezometers located in the Ledo-Paniselian-Brusselian aquifer, we see that although the pumping is concentrated in the south, it causes the water level to decrease far northwards, which implies a higher hydraulic conductivity of this aquifer than the Oligocene aquifer. Several conceptual improvements to the model were performed. The detailed geometry of the Oligocene aquifer and Bartoon aquitard system was introduced in the model
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Directory of Open Access Journals (Sweden)
Fernandes, P.
2008-06-01
Full Text Available The synclinal basin of Kourimat, subdivided in two sub-basins (Igounzar in the North, and Zeltene in the South, is situated in the oriental part of Essaouira basin shelters a carbonate aquifer system contained in the limestones and dolomitic limestones of the Cenomanian and the Turonian. These ground waters represent the only drinking water and irrigation resource for the region.The geological formations outcropping in the studied area, start with the clay and marly formations of the terminal Jurassic in the south of Zelten watershed, and end with the sandy and loamy Quaternary formations in coastal areas in the Low Qsob watershed. The Middle and Upper Cretaceous (marl, fractured limestone, and dolomites represent the rest of the stratigraphic series especially in the areas of the Igrounzar watershed (up to 85% of the outcrops and in Zelten (up to 50%.The field occupation is not very significant. It basically consists of three types: 1 cultures (essentially cereals where it is possible (on the marly soils of the Cretaceous, the Quaternary and the Eocene; 2 uncovered areas corresponding to the fissured and karstic limestone outcrops of the Cretaceous and the Jurassic formations, and 3 forests (coniferous trees in the downstream part of the catchments area (Plio-quaternary soils and mountainous reinforcements of the Western High Atlas. Like for other undeveloped areas of Morocco, the Meskala basin is also subjected to an intensive deforestation (wood for heating and cooking.The study undertaken on the Cenomano-turonian aquifer has allowed us to characterize it from the hydrodynamical, hydrogeological and hydrogeochemical point of view. The piezometric map of the two regrouped aquifer levels shows water flow senses from the SE to the NW. The hydraulic gradient varies from upstream to downstream, being weak n the central zone relative to the best hydrodynamic characteristics. The time evolution of the piezometry shows annual and seasonal