Multi‐depth monitoring of electrical conductivity and temperature of groundwater at a multilayered coastal aquifer: Jeju Island,Korea     

Kue‐Young Kim  Chul‐Min Chon  Ki‐Hwa Park  Yun‐Seok Park  Nam‐Chil Woo 《水文研究》2008,22(18):3724-3733

To supplement conventional geophysical log data, this study presents temporal variations in electrical conductivity (EC) and temperature with depth in a multilayered coastal aquifer, on the eastern part of Jeju Island, Korea. One‐month time‐series data obtained at eight points from a multi‐depth monitoring system showed that semidiurnal and semimonthly tidal variations induced dynamic fluctuations in EC and temperature. At some depths, EC ranged from 1483 to 26 822 µS cm^?1, while some points showed no significant variations. The results of EC log and time‐series data revealed that a sharp fresh‐saltwater interface occurred at low tide, but the diffusion zone broadened to 20 m at high tide. EC, temperature, and tide level data were used for the cross‐correlation analysis. The response time of EC and temperature to tide appears to range from less than 30 min to 11 h. Using end‐member mixing analysis (EMMA), the fraction of variations of chloride concentration in the multilayered aquifer was explained, and a conceptual model was developed which subdivided the coastal aquifer into four vertical zones. The percentage of water derived from seawater varied from 2 to 48 at specific depth, owing to tidal fluctuations. Continuous observations of EC and temperature at multiple depths are powerful tools for quantifying the transport of saline water by tidal variations in multilayered coastal aquifers. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Preliminary investigation of Late Pleistocene fauna from Ryonggok Cave No. 1, Sangwon County,North Hwanghae Province,Democratic People's Republic of Korea     

Rye Sun Choe  Kum Sik Han  Se Chan Kim  Myong Hyok Ri  Jae Nam Ri 《第四纪科学杂志》2021,36(6):1137-1142

The investigation of a limestone cave on the Ryonggok-ri of Sangwon County, North Hwanghae Province, DPRK, has yielded many faunal remains including Late Pleistocene deer, brown bears and horses. Uranium series dating of fossil teeth yielded dates of ~72ka at the base of Layer 2 – the bone-bearing unit – and ~44ka at the top. The rich and diverse mammal remains of Ryonggok Cave No. 1 are indicative of warm and humid temperate conditions during the Late Pleistocene, and reflect the presence of both dense forests and open grassland. In addition, pollen and spores from the site include two families and 24 genera of trees, six families and a genus of grasses and herbs, and two families and six genera of ferns, corroborating the environments inferred from the faunal remains.  相似文献   

Changes in the distribution of cold waves in France in the middle and end of the 21st century with IPSL-CM5 and CNRM-CM5 models     

S. Parey  T. T. H. Hoang 《Climate Dynamics》2016,46(3-4):879-896

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Novel integrated approaches for predicting the compressibility of clay using cascade forward neural networks optimized by swarm- and evolution-based algorithms     

He  Ziguang  Nguyen  Hoang  Vu  Thai Ha  Zhou  Jian  Asteris  Panagiotis G.  Mammou  Anna 《Acta Geotechnica》2022,17(4):1257-1272

Acta Geotechnica - Soft soils are considered as disadvantages in construction, especially in clay layers. It requires many advanced techniques to treat the soft soils before construction, aiming to...  相似文献   

A New Natural Secondary Reference Material for Garnet U-Pb Dating by TIMS and LA-ICP-MS     

Namık Aysal  Marcel Guillong  Tamara Bayanova  Mayuko Fukuyama  Nicole Leonard  İsak Yılmaz  Elif Varol  Fatma Şişman Tükel  Yusuf Kaan Kadıoğlu  Nurullah Hanilçi  Fulya Uzun  Ersin Kaygısız 《Geostandards and Geoanalytical Research》2023,47(2):297-310

Gem quality andradite-rich garnet (IUC-1), obtained from the Miocene trachyte dome near Ankara city (Turkey), has been identified as a potential natural secondary reference material for U-Pb dating. In this study, U-Pb dating was performed in five different laboratories using isotope dilution TIMS and laser ablation ICP-MS to determine the homogeneity of euhedral garnet crystals. The U-Pb ID-TIMS data for IUC-1 yielded ²⁰⁷Pb/²³⁵U and ²⁰⁶Pb/²³⁸U ages of 20.9 ± 0.4 and 20.6 ± 0.8 Ma respectively, and these values are consistent with U-Pb LA-ICP-MS analyses, in which different garnet crystals yielded ages of 20.8 ± 0.1, 20.7 ± 0.1, 20.7 ± 0.2 and 20.2 ± 0.1 Ma. An andradite (IUC-2) from the Serçeören wollastonite skarn (Turkey) can be used as a secondary reference material provided detailed imaging of the crystals is undertaken. ID-TIMS data yielded ²⁰⁷Pb/²³⁵U and ²⁰⁶Pb/²³⁸U ages of 20.4 ± 0.4 and 20.9 ± 1.0 Ma respectively, and yielded U-Pb ages on different grains of 20.5 ± 0.1, 20.7 ± 1.0, 20.8 ± 1.7 and 20.9 ± 1.6 Ma. The assigned weighted mean age of IUC-1 (20.4 ± 0.5 Ma, 2s) is proposed as a 2023 reference value. IUC-1 garnet is expected to contribute significantly to rapidly developing garnet geochronology in the near future.  相似文献   

Comparison of testing techniques and models for establishing the SWCC of riverbank soils     

Soonkie Nam  Marte Gutierrez  Panayiotis Diplas  John Petrie  Alexandria Wayllace  Ning Lu  Juan Jorge Muñoz 《Engineering Geology》2010,110(1-2):1-10

The soil water characteristic curve (SWCC), also known as soil water retention curve (SWRC), describes the relationship between water content and soil suction in unsaturated soils. Water content and suction affect the permeability, shear strength, volume change and deformability of unsaturated soils. This paper presents results of the laboratory determination of the SWCC for soil samples obtained from the riverbank of the Lower Roanoke River in North Carolina. Six different testing methods were used to establish the SWCC including the filter paper, dewpoint potentiameter, vapor equilibrium, pressure plate, Tempe cell and osmotic methods. It is concluded that each suction measurement technique provides different measurable ranges of suction values, and the combined results from the different tests provide continuous SWCCs. Three widely available models were also shown to adequately fit the experimental SWCC data, particularly for matric suction values under 1500 kPa. These results will be valuable to practitioners in deciding which methods to use to establish the SWCC, and which empirical relationship to use for modeling the SWCC of riverbank soils.  相似文献   

Modele circulaire de source sismique     

Hoang Trong Pho  Hilaire Legros 《Pure and Applied Geophysics》1974,112(2):380-394

Résumé On donne l'expression du déplacement dû à la propagation d'une dislocation uniforme partant du centre d'une faille circulaire, avec une vitesse de propagation finie ou infinie. Dans cedernier cas on se trouve dans une situation analogue à celle de la diffraction de Fraunhofer en Optique. Le spectre d'amplitude de l'ondeP est modulé dans son détail par la fonction de Bessel d'ordre1. Quand le rayon du cercle est relativement faible, on retrouve les expressions d'une source ponctuelle, dans lesquelles la densité surfacique de moment intégré est remplacé par le moment sismique total. On met en évidence une fréquence de coupure qui augmente avec la profondeur du foyer et diminue quand le rayon de la faille augmente. On donne enfin une expression du moment sismique total en fonction de l'amplitude spectrale aux basses fréquences.

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Summary We have examined the case of the radial propagation of a uniform dislocation and stated in detail the expression of the displacement. The rupture velocity is assumed finite or infinite. The last case shows some analogies with the Fraunhofer diffraction. TheP wave amplitude spectrum is modulated in its detail by theJ ₁ Bessel function. With small values of the radius, one can obtain the displacement by replacing in the expression corresponding to point sources the integral of the moment density by the total seismic moment. The corner frequency increases with the focal depth, and decreased when the fault radius increases. Finally, we give an expression of the total seismic moment deduced from the low frequency spectral amplitude components.

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Velocity and attenuation in partially saturated rocks: poroelastic numerical experiments     

Hans B. Helle  Nam H. Pham  José M. Carcione 《Geophysical Prospecting》2003,51(6):551-566

We use a poroelastic modelling algorithm to compute numerical experiments on wave propagation in a rock sample with partial saturation using realistic fluid distribution patterns from tomography scans. Frequencies are in the range 10 to 500 kHz. The rock is a homogeneous isotropic sandstone partially filled with gas and water, which are defined by their characteristic values of viscosity, compressibility and density. We assume no mixing and that the two different pore-fills occupy different macroscopic regions. The von Kármán self-similar correlation function is used, employing different fractal parameters to model uniform and patchy fluid distributions, respectively, where effective saturation is varied in steps from full gas to full water saturation. Without resorting to additional matrix–fluid interaction mechanisms, we are able to reproduce the main features of the variation in wave velocity and attenuation with effective saturation and frequency, as those of published laboratory experiments. Furthermore, the behaviour of the attenuation peaks versus water saturation and frequency is similar to that of White's model. The conversion of primary P-wave energy into dissipating slow waves at the heterogeneities is shown to be the main mechanism for attenuating the primary wavefield. Fluid/gas patches are shown to affect attenuation more than equivalent patches in the permeability or solid-grain properties.  相似文献   

How are storm time injections different from nonstorm time injections?     

D.-Y. Lee  J.A. Hwang  E.S. Lee  K.W. Min  W.Y. Han  U.W. Nam 《Journal of Atmospheric and Solar》2004,66(18):1715

One of the key elements of storms and substorms is the injection of energetic particles into the region of near geosynchronous orbit, that is, the sudden flux enhancement in the energy range of tens to hundreds of keV. This paper reports the observational results on how such injection features during storm times are different from those of nonstorm times. We particularly focus on the difference between proton injections and electron injections. Based on a number of storm time injection events that meet our strict selection criteria, we find a notable difference between proton injections and electron injections in the energy-spectral dependence of the flux enhancement averaged over the first 30 min after the injection onset: The average flux enhancement of many protons injections tends to be bigger at higher energy channels than at lower energy channels, but electron injections exhibit the opposite tendency for the energy-spectral dependence of flux enhancement, i.e., average flux enhancement decreasing with increasing energy. We show that this feature is almost unique only for the injection events during the storm main and early recovery phase. It is suggested that any successful scenario intended to model storm time injections should be able to explain this difference between proton injections and electron injections.  相似文献   

Fusion of multispectral and panchromatic Satellite images using the curvelet transform   总被引：18，自引：0，他引：18  

Myungjin Choi Rae Young Kim Myeong-Ryong Nam Hong Oh Kim 《Geoscience and Remote Sensing Letters, IEEE》2005,2(2):136-140

A useful technique in various applications of remote sensing involves the fusion of different types of satellite images, namely multispectral (MS) satellite images with a high spectral and low spatial resolution and panchromatic (Pan) satellite image with a low spectral and high spatial resolution. Recent studies show that wavelet-based image fusion provides high-quality spectral content in fused images. However, the results of most wavelet-based methods of image fusion have a spatial resolution that is less than that obtained via the Brovey, intensity-hue-saturation, and principal components analysis methods of image fusion. We introduce an improved method of image fusion which is based on the amelioration de la resolution spatiale par injection de structures (ARSIS) concept using the curvelet transform, because the curvelet transform represents edges better than wavelets. Because edges are fundamental in image representation, enhancing the edges is an effective means of enhancing spatial resolution. Curvelet-based image fusion has been used to merge a Landsat Enhanced Thematic Mapper Plus Pan and MS image. The proposed method simultaneously provides richer information in the spatial and spectral domains.  相似文献