Intrinsic random function of order<Emphasis Type="Italic"> k</Emphasis> kriging of electrical resistivity data for estimating the extent of saltwater intrusion in a coastal aquifer system     

Byoung?Ohan?ShimEmail author  Sang?Yong?Chung  Hee?Joon?Kim  Ig?Hwan?Sung 《Environmental Geology》2004,46(5):533-541

A saltwater intrusion study using electrical resistivity distribution was conducted in a coastal aquifer system in the southeastern part of Busan, Korea. This aquifer system is divided into four layers according to the hydrogeologic characteristics, and the horizontal extent of intruded saltwater is determined at each layer through the geostatistical interpretation of electrical resistivity data. Intrinsic random function of order k (IRF-k) kriging is performed with covariance models to produce the plane of spatial mean resistivities. The kriged estimates are evaluated by cross validation, and they showed a good agreement with the true values. The statistics of cross validation represented low errors for the estimates. In the resistivity contour maps more than 5 m below the surface, a dominant direction of saltwater intrusion was observed beginning from the east side. These results led the authors to conclude that the application of geostatistical technique to electrical resistivity data is useful for assessing saltwater intrusion in a coastal aquifer system.  相似文献   

Electromagnetic fields in a non-uniform steel-cased borehole   总被引：1，自引：0，他引：1  

Hee Joon Kim  Ki Ha Lee 《Geophysical Prospecting》2006,54(4):433-439

Since most oil wells are cased in steel, electromagnetic (EM) signals undergo severe attenuation as they diffuse across the casing. This paper examines an effect of non‐uniform casing properties on EM fields measured in a steel‐cased well embedded in a layered formation. We use a finite‐element method for computing secondary azimuthal electric fields in a cylindrically symmetric model, and analytically obtain primary fields for a homogeneous casing in a homogeneous whole space. Although steel casing largely masks EM signals induced into a layered formation, the induced signal is more pronounced in phase than in amplitude. The effect of casing non‐uniformity is quite large in measured fields but is highly localized. When electrical conductivity varies rapidly in the casing wall, the resulting EM fields also vary rapidly. A cross‐correlation function of these variations has strong peaks at two points, the interval between them being equal to the source–receiver distance. The high‐frequency coherent noise event caused by the non‐uniform casing can be greatly suppressed by low‐pass filtering to enhance EM signals indicating formation conductivity.  相似文献   

Modified Biot-Gassmann Theory for Calculating Elastic Velocities for Unconsolidated and Consolidated Sediments*   总被引：1，自引：0，他引：1  

Lee  Myung W. 《Marine Geophysical Researches》2002,23(5-6):403-412

Marine Geophysical Research - The classical Biot-Gassmann theory (BGT) generally overestimates shear-wave velocities of water-saturated sediments. To overcome this problem, a new theory is...  相似文献   

Thrust geometries in unconsolidated Quaternary sediments and evolution of the Eupchon Fault, southeast Korea   总被引：1，自引：0，他引：1  

Young-Seog  Kim  Joon Young  Park  Jeong Hwan  Kim  Hyeon Cho  Shin  David J.  Sanderson 《Island Arc》2004,13(3):403-415

Abstract The Korean peninsula is widely regarded as being located at the relatively stable eastern margin of the Asian continent. However, more than 10 Quaternary faults have recently been discovered in and reported from the southeastern part of the Korean Peninsula. One of these, the Eupchon Fault, was discovered during the construction of a primary school, and it is located close to a nuclear power plant. To understand the nature and characteristics of the Quaternary Eupchon Fault, we carried out two trench surveys near the discovery site. The fault system includes one main reverse fault (N20°E/40°SE) with approximately 4 m displacement, and a series of branch faults, cutting unconsolidated Quaternary sediments. Structures in the fault system include synthetic and antithetic faults, hanging‐wall anticlines, drag folds, back thrusts, pop‐up structures, flat‐ramp geometries and duplexes, which are very similar to those seen in thrust systems in consolidated rocks. In the upper part of the fault system, several tip damage zones are observed, indicating that the fault system propagates upward and terminates in the upper part of the section. Pebbles along the main fault plane show a preferred orientation of long axes, indicating the fault trace. The unconformity surface between the Quaternary deposits and the underlying Tertiary andesites or Cretaceous sedimentary rocks is displaced by this fault with a reverse movement sense. The stratigraphic relationship shows normal slip sense at the lower part of the section, indicating that the fault had a normal slip movement and was reversely reactivated during the Quaternary. The inferred length of the Quaternary thrust fault, based on the relationship between fault length and displacement, is 200–2000 m. The current maximum horizontal compressive stress direction in this area is generally east‐northeast–west‐southwest, which would be expected to produce oblique slip on the Eupchon Fault, with reverse and right‐lateral strike‐slip components.  相似文献   

Surveillance of waste disposal activity at sea using satellite ocean color imagers: GOCI and MODIS     

Gi Hoon Hong  Dong Beom Yang  Hyun-Mi Lee  Sung Ryull Yang  Hee Woon Chung  Chang Joon Kim  Young-Il Kim  Chang Soo Chung  Yu-Hwan Ahn  Young-Je Park  Jeong-Eon Moon 《Ocean Science Journal》2012,47(3):387-394

Korean Geostationary Ocean Color Imager (GOCI) and Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua observations of the variation in ocean color at the sea surface were utilized to monitor the impact of nutrient-rich sewage sludge disposal in the oligotrophic area of the Yellow Sea. MODIS revealed that algal blooms persisted in the spring annually at the dump site in the Yellow Sea since year 2000 to the present. A number of implications of using products of the satellite ocean color imagers were exploited here based on the measurements in the Yellow Sea. GOCI observes almost every hour during the daylight period, every day since June 2011. Therefore, GOCI provides a powerful tool to monitor waste disposal at sea in real time. Tracking of disposal activity from a large tanker was possible hour by hour from the GOCI timeseries images compared to MODIS. Smaller changes in the color of the ocean surface can be easily observed, as GOCI resolves images at smaller scales in space and time in comparison to polar orbiting satellites, e.g., MODIS. GOCI may be widely used to monitor various marine activities in the sea, including waste disposal activity from ships.  相似文献   

Distribution of persistent organic pollutants in bivalves from the northeast coast of China   总被引：1，自引：0，他引：1  

Jin Y  Hong SH  Li D  Shim WJ  Lee SS 《Marine pollution bulletin》2008,57(6-12):775-781

To assess the levels of organochlorine compounds (OCs) in the Chinese coastal environment, monitoring study using bivalves was conducted in 2005. A total of 21 bivalve samples covering the northeastern coast of China were collected and analyzed. Organochlorine compounds were widely distributed in the Chinese coastal environment, with dichlorodiphenyltrichloroethane (DDT) contamination being particularly prevalent. The overall concentrations of PCBs, DDTs, HCHs, chlordane compounds (CHLs), dieldrin, and endosulfans in bivalves were in the ranges of 3.27-25.4, 54.8-2680, 1.42-25.5, n.d. (not detected)-2.28, n.d.-4.02, and n.d.-9.55 ng g(-1) on a dry weight basis, respectively. The concentrations of DDT and HCH compounds are relatively higher than those from the coastal areas of other Asian countries. DDT metabolites were predominant, suggesting that the degradation of DDT is in progress in the Chinese coastal environment. Still, however, DDTs of high concentration exceeding 1000 ng g(-1) were observed at 19% of the stations surveyed. Among HCH compounds, beta-HCH, which is an isomer with strong persistency, was observed predominantly. Compositions of DDT and HCH compounds imply that fresh input of the two compounds into the Chinese coasts is possibly low.  相似文献   

The Development of Anoxia in the Artificial Lake Shihwa, Korea, as a Consequence of Intertidal Reclamation     

Myung Woo Han  Yong Chul Park 《Marine pollution bulletin》1999,38(12):187-1199

The reclamation of an intertidal flat recently created Lake Shihwa, in Kyunggi province, on the western coast of Korea. The artificial, saline lake was expected to transform into a freshwater one. However, the drainage structure of the lake does not allow entrapped Yellow Sea water to be fully replaced by freshwater from its hinterland. The lake water is strongly stratified with polluted freshwater at the surface and entrapped, saline water on the bottom. The pycnocline, lying at a depth range of 6–8 m, prevents mixing between the two water bodies, and thus generates anoxic conditions in the deeper waters. The pycnocline matches the oxic/anoxic interface between the oxygenated surface water and the hydrogen sulphide rich deep water. Stratification, the inflow of polluted water, and anoxia all contribute to the disastrous pollution of the lake.  相似文献   

Extraction of agar from Eucheuma cottonii and Gelidium amansii seaweeds with sonication pretreatment using autoclaving method     

Din  Siti Sabariah  Chew  Kit Wayne  Chang  Yu-Kaung  Show  Pau Loke  Phang  Siew Moi  Juan  Joon Ching 《中国海洋湖沼学报》2019,37(3):871-880

The effect of sonication pretreatment condition on Eucheuma cottonii and Gelidium amansii seaweed towards agar extraction wae studied. Four parameters were changed during sonication to investigate the effects on agar yield and quality. These parameters include the time interval, concentration ratio, frequency, and intensity. The highest amount of agar extracted from Eucheuma cottonii species could be obtained from the time interval of 30 min, seaweed weight to solvent volume ratio of 1:20, the frequency of 35 Hz, and the sonication power intensity of 30%. For Gelidium amansii species, the best agar yield also could be obtained from the time interval of 30 min, 1:20 of seaweed weight to water volume ratio, the frequency of 35 Hz, and power intensity of 30%. From the experiment, sonication pretreatment significantly influenced the yield and properties of extracted agar. The sonication with autoclaved seaweed produced agar containing less sulfate content, which is an excellent chemical property for gel electrophoresis applications.The gel strength of sonication with autoclaving for both seaweeds, Eucheuma and Gelidium species was the highest among those by sonication with direct heating, which proved that sonication pretreatment with autoclaving could enhance the physical properties of the agar.  相似文献