Well modeling and estimation of hydraulic parameters     

Stephan Schumacher  Marián Slodička  Uwe Jaekel 《Computational Geosciences》1997,1(3-4):317-331

A general model for time‐dependent saturated–unsaturated waterflow caused by a single well with a given radius is presented. The storage capacity of the well tube is taken into account. The inflow into the well (with drainage) is modeled using the Signorini boundary condition. The nonconforming mixed finite element method on a multilevel adaptive grid is used for the solution of the radial symmetric, time dependent problem. Finally, van Genuchten parameters of an aquifer are determined from field measurements by inverse computations.  相似文献   

Relationship between positive cerium anomaly and adsorbed water in Antarctic lunar meteorites     

HIROYUKI KAGI  KAZUYA TAKAHASHI 《Meteoritics & planetary science》1998,33(5):1033-1040

Abstract— Concentrations of adsorbed water in single mineral grains of Antarctic lunar meteorites were determined with micro infrared (IR) spectroscopy. A relationship was found between the mineral's ability to adsorb water and the extent of Ce anomaly in rare earth element (REE) patterns precisely determined by the isotope dilution method using a thermal ionization mass spectrometer. Asuka (A) 881757, a lunar meteorite from the mare basalt without Ce anomaly, showed no trace of IR absorption due to adsorbed water. On the contrary, Yamato (Y) 791197-109, Y-86032-98, Y-86032-95, Y-791197-115 and Y-82192-55A from the lunar highland exhibiting positive Ce anomaly showed IR absorption due to adsorbed water in some of their minerals. The detected water would be of terrestrial origin, because it was not structurally bound and easy to exchange judging from the spectral band shape. The contrast in concentration of adsorbed water between the lunar highland and the mare basalt is derived from a difference in the density of microfractures in mineral grains. Average concentrations of adsorbed water in the lunar highland meteorites were 3.8 mg/cm³ for pyroxene and olivine, and 1.7 mg/cm³ for plagioclase. This contrast between minerals is noteworthy because it has been known that Ce anomaly of pyroxene and olivine is larger than that of plagioclase both for Antarctic lunar meteorites and some lunar rocks. Furthermore, more adsorbed water was detected for minerals in meteorites that exhibit larger Ce anomaly. The present observations demonstrate that the extent of Ce anomaly correlated with the concentration of adsorbed water, which suggests that active mineral surface resulting in adsorption of water could be a trace of interaction forming Ce anomaly. Terrestrial weathering on Antarctica and REE fractionation on the Moon are discussed for possible origins of the Ce anomaly.  相似文献   

Reconstructions of the Mediterranean Outflow Water during the quaternary based on the study of changes in buried mounded drift stacking pattern in the Gulf of Cadiz     

Estefania Llave  Francisco J. Hernández-Molina  Dorrik A. V. Stow  Mari Carmen Fernández-Puga  Margarita García  Juan T. Vázquez  Adolfo Maestro  Luis Somoza  Victor Díaz del Río 《Marine Geophysical Researches》2007,28(4):379-394

Contourite deposits in the central sector of the middle slope of the Gulf of Cadiz have been studied using a comprehensive acoustic, seismic and core database. Buried, mounded, elongated and separated drifts developed under the influence of the lower core of the Mediterranean Outflow Water are preserved in the sedimentary record. These are characterised by depositional features in an area where strong tectonic and erosive processes are now dominant. The general stacking pattern of the depositional system is mainly influenced by climatic changes through the Quaternary, whereas changes in the depositional style observed in two, buried, mounded drifts, the Guadalquivir and Huelva Drifts, are evidence of a tectonic control. In the western Guadalquivir Drift, the onset of the sheeted drift construction (aggrading QII unit) above a mounded drift (prograding QI unit) resulted from a new Lower Mediterranean Core Water hydrodynamic regime. This change is correlated with a tectonic event coeval with the Mid Pleistocene Revolution (MPR) discontinuity that produced new irregularities of the seafloor during the Mid- to Late-Pleistocene. Changes in the Huelva Drift from a mounded to a sheeted drift geometry during the Late-Pleistocene, and from a prograding drift (QI and most part of QII) to an aggrading one (upper seismic unit of QII), highlight a new change in oceanographic conditions. This depositional and then oceanographic change is associated with a tectonic event, coeval with the Marine Isotope Stage (MIS) 6 discontinuity, in which a redistribution of the diapiric ridges led to the development of new local gateways, three principal branches of the Mediterranean Lower Core Water, and associated contourite channels. As a result, these buried contourite drifts hold a key palaeoceanographic record of the evolution of Mediterranean Lower Core Water, influenced by both neotectonic activity and climatic changes during the Quaternary. This study is an example of how contourite deposits and erosive elements in the marine environment can provide evidence for the reconstruction of palaeoceanographic and recent tectonic changes.  相似文献   

Magnetic studies and scanning electron microscopy — X-ray energy dispersive spectroscopy analyses of road sediments,soils and vehicle-derived emissions   总被引：1，自引：0，他引：1  

Marcos A. E. Chaparro  Débora C. Marié  Claudia S.G. Gogorza  Ana Navas  Ana M. Sinito 《Studia Geophysica et Geodaetica》2010,54(4):633-650

Human health and environmental problems related to particulate matter emission from vehicles has become a topic of research interest in recent years. These airborne particles can not only be directly inhaled, but are also present as suspended and deposited particles on paved areas and roadside soils. Here we report on magnetic studies, scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS) and chemical analyses of vehicle-derived particles collected from both primary sources and as deposited particles on roads and soils. Preliminary results, recently published by the authors, have revealed that the magnetic signal of such particles is controlled by a magnetite-like phase with magnetic grain size ranging between 0.1 μm and 5 μm. An enrichment of some trace elements: Ba, Cr, Cu, Zn and Pb was also found. In this study we focus on SEM and EDS complementary studies of magnetic extracts. SEM observations showed small individual particles or spherulites, small aggregates in the form of chains or clusters, large aggregates of spherules, flake-like bodies, fibre-like particles, sheet-like particles, irregular debris and large particle agglomerates, i.e. a wide variety of shapes. Grain size distribution is also in agreement with magnetic grain size estimations. Additionally the following elements: C, O, Na, Mg, Al, Si, S, K, Ca, V, Ba, Ti, Cr, Mn, Fe, Cu, Zn and Pb were detected by EDS analysis.  相似文献   

Can a strong atmospheric CO₂ rectifier effect be reconciled with a "reasonable" carbon budget?   总被引：1，自引：1，他引：0  

A. SCOTT DENNING  TARO. TAKAHASHI  PIERRE FRIEDLINGSTEIN 《Tellus. Series B, Chemical and physical meteorology》1999,51(2):249-253

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Generation of block and ash flows during the 1990–1995 eruption of Unzen Volcano, Japan     

Tadahide Ui  Norimichi Matsuwo  Mari Sumita  Akihiko Fujinawa 《Journal of Volcanology and Geothermal Research》1999,89(1-4)

Processes generating block and ash flows by gravitational dome collapse (Merapi-type pyroclastic flow) were observed in detail during the 1990–1995 eruption of Unzen volcano, Japan. Two different types were identified by analysis of video records and observations during helicopter flights. Most of the block and ash flows erupted during the 1991–1993 exogenous dome growth stage initially involved crack propagation due to cooling and flowage of the dome lava lobes. The mass around the crack became unstable, locally decreasing in tensile strength. Finally, a slab separated from the lobe front, fragmented progressively from the base to the top within a few seconds, and became a block and ash flow. Rock falls immediately followed, in response to local instability of the lobe front. Clasts in these rock falls fragmented and merged with the preceding flow. In contrast, block and ash flows during the endogenous dome growth stage in 1994 were generated due to local bulge of the dome. Unstable lava blocks collapsed and subsequently fragmented to produce block and ash flows.  相似文献   

新西海桥的非线性地震响应分析     

吴庆雄  陈宝春  高桥和雄 《地震工程与工程振动》2008,28(5)

本文讨论了日本第一座公路钢管混凝土拱桥——主跨230m的新西海桥的非线性地震响应特性。采用三维有限元计算模型,用纤维单元法考虑钢管混凝土的材料非线性,用P-δ效应考虑几何非线性,讨论了在纵桥向地震作用、横桥向地震作用以及纵、横桥两方向同时作用情况下该桥的非线性地震响应特性和抗震性能。计算表明,在纵桥向地震作用时轴力的作用显著,拱脚附近产生的内力较大;而横桥向地震作用时轴力和面外弯矩作用显著,拱脚以及拱肋与桥面连接附近产生的内力较大;横向地震响应远大于纵向地震响应;应考虑纵、横桥向地震力共同作用的影响。  相似文献   

Hazards and landscape changes (degradations) on Hungarian karst mountains due to natural and human effects     

Móga JNOS  Kiss KLAUDIA  Szabó MRIA  Kériné Borsodi ANDREA  Kéri ANDRS  Mari LSZLó  Knáb MóNIKA  Iván VERONIKA 《山地科学学报》2013,10(1):16-28

In order to study the karstological processes within the karst ecological system,the geohazards and degradation of karst landscapes on the karst areas of the Bakony mountains(Hungary),we investigated the abiotic elements of the environment,soil and cover deposits,erosion soil decay;the changes in the quantity and quality of karst waters:contamination at swallow holes,contamination of karst springs;and the biogenic factors:surface vegetation coverage by the corine land cover method,plant-ecological examinations,qualification of surface waters with the help of biological water labeling.We recognized that the increasing human activities during the past few centuries have had significant impact on the investigated landscapes of karst areas because of their spatial sensitivity.In the scope of our research we concluded that the landscape changes due to natural and human effects can vary strongly on the different karst areas.These differences can arise from the climatic and geomorphologic situation,the coverlayer’s qualities,etc.,but primarily from the different utilization of the investigated karst areas(e.g.the intensity,characteristics and territorial extension of utilization).On the spot investigation we detected traces of new and fast geomorphological processes(gully formation,landslides,collapses,new sinkhole development) and landforms(sinkholes,gullies,swallow holes),which are clear evidences of the effect of climatic changes.  相似文献   

Variations in turbulent kinetic energy at a point source submarine groundwater discharge in a reef lagoon     

Sabrina M. Parra  Ismael Mariño-Tapia  Cecilia Enriquez  Arnoldo Valle-Levinson 《Ocean Dynamics》2014,64(11):1601-1614

The influence of sea level variations due to tides and wave setup on turbulent kinetic energy (TKE) was observed at a point source submarine groundwater discharge in a fringing coral reef lagoon. Tidal and wave setup variations modulated speed, TKE, TKE dissipation, and water temperature and salinity at the buoyant jet. The primary driver of jet TKE and speed variations was tides, while wave setup was a minor contributor. An inverse relationship between surface elevation and TKE was explained with an exponential equation based on sea level variations. During low tides, peak jet speeds (up to 0.3 m s^?1) and TKE per unit mass (up to 0.4 m² s^?2) were observed. As high tide approached, the jet produced minimum TKE of ~0.003 m² s^?2 and TKE dissipation ranged from 2 to 8×10^?4 m² s^?3. This demonstrated the sensitivity of the jet discharge to tides despite the small tidal range (<20 cm). Jet temperatures and salinities displayed semidiurnal oscillations with minimum salinity and temperature values during maximum discharge. Jet salinities increased throughout low tides while temperatures decreased. This pattern suggested the jet conduit was connected to a stratified cavity within the aquifer containing cool fresh water over cool salty water. As low tides progressed, jet outflow increased in salinity because of the mixing within the conduit, while lower jet temperatures suggested water coming from further or deeper in the aquifer. The presence of such a cavity has been recently confirmed by divers.  相似文献   

Physical property anisotropy of foliated fault rocks: Study from the Nobeoka Thrust,Shimanto Belt,southwest Japan          下载免费PDF全文

Mari Hamahashi  Wataru Tanikawa  Yohei Hamada  Yoshitaka Hashimoto  Saneatsu Saito  Gaku Kimura 《Island Arc》2018,27(5)

To investigate the physical property anisotropies of foliated fault rocks in subduction zones, the hanging wall phyllites and footwall cataclasites exhumed along the Nobeoka Thrust, a fossilized out‐of‐sequence‐thrust in the Shimanto Belt, Japan, was focused. Discrete physical property (electric resistivity, P‐ and S‐wave velocities, and porosity) measurements were conducted employing geologic coordinates (depth‐parallel direction, strike direction, and maximum dip direction of foliation), using the core samples obtained from the Nobeoka Thrust Drilling Project and compared the data to borehole geophysical logs. A higher sample P‐wave velocity (Vp), lower S‐wave velocity (Vs), higher Vp/Vs, and lower sample porosity and resistivity compared to the logs, are inferred to have been caused by the larger sampling scale of the logs and lower fluid saturation of the borehole. The phyllites and cataclasites exhibited substantial vertical and horizontal anisotropy of Vp (0.4–17.3 % and 2.7–13.8 %, respectively), Vs (0.5–56 % and 7.7–43 %, respectively), and resistivity (0.9–119 % and 2.0–65.9 %, respectively). The physical property anisotropies are primarily affected by the dip angles of foliation. The fault rocks that have gentler dip angles exhibit a higher Vp in the strike and maximum dip direction and a lower Vp in the depth‐parallel direction. In contrast, the fault rocks that have steeply dipping structures show a higher Vp in the strike and depth‐parallel directions with a lower velocity in the maximum dip direction. Resistivity anisotropy show a trend opposite to that of the Vp in relation to the dip angles. Our results show lower Vp anisotropy than those obtained in previous studies, which measured wave speeds perpendicular or parallel to foliation under confining pressure. This study highlights the significance of dip angles on vertical properties in geophysical surveys across foliated fault rocks.  相似文献