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251.
Glauconite grains are an important component of the surficial sediments on the Korean continental shelf. Relatively high
glauconite contents (>20%) occur near Huksan Island in the Yellow Sea and on the outer shelf of the southern East Sea where
they are associated with relict, sandy sediments. By contrast, glauconite grains are rare (<1%) in clay-dominated sediments.
The grains can be classified into four major categories: (1) very abundant, green to dark green, spheroidal and lobate grains
displaying bulbous and honeycomb exteriors with well-developed surface cracks; (2) dark green, discoidal grains with poorly
defined cracks; (3) scarce, moderately dark green, accordion-shaped grains characterized by series of closely spaced, parallel
surface ridges; (4) scarce, green to dark green, foraminifer-shaped grains. Microprobe analyses as well as optical microscopy
and SEM observations show that most grains are composed of mineral mixtures (e.g., quartz, mica, feldspar) rather than a single
mineral species. The mineralogy, morphology, and textural properties suggest that the grains may have formed mainly by replacement
of fecal pellets, and the alteration of mica and clays which have filled foraminifera tests. The high potassium contents,
rosette-shaped clay structures, and bulbous shapes reflect an “evolved” (mature) stage of glauconitization. Glauconite grains
in Korean shelf sediments are presumably relict, and have been produced by the reworking of older glauconitic sediments during
the Holocene sea-level transgression.
Received: 4 October 1999 / Revision accepted: 18 May 2000 相似文献
252.
Spatially distributed long‐term hydrologic simulation using a continuous SCS CN method‐based hybrid hydrologic model 下载免费PDF全文
A continuous Soil Conservation Service (SCS) curve number (CN) method that considers time‐varied SCS CN values was developed based on the original SCS CN method with a revised soil moisture accounting approach to estimate run‐off depth for long‐term discontinuous storm events. The method was applied to spatially distributed long‐term hydrologic simulation of rainfall‐run‐off flow with an underlying assumption for its spatial variability using a geographic information systems‐based spatially distributed Clark's unit hydrograph method (Distributed‐Clark; hybrid hydrologic model), which is a simple few parameter run‐off routing method for input of spatiotemporally varied run‐off depth, incorporating conditional unit hydrograph adoption for different run‐off precipitation depth‐based direct run‐off flow convolution. Case studies of spatially distributed long‐term (total of 6 years) hydrologic simulation for four river basins using daily NEXRAD quantitative precipitation estimations demonstrate overall performances of Nash–Sutcliffe efficiency (ENS) 0.62, coefficient of determination (R2) 0.64, and percent bias 0.33% in direct run‐off and ENS 0.71, R2 0.72, and percent bias 0.15% in total streamflow for model result comparison against observed streamflow. These results show better fit (improvement in ENS of 42.0% and R2 of 33.3% for total streamflow) than the same model using spatially averaged gauged rainfall. Incorporation of logic for conditional initial abstraction in a continuous SCS CN method, which can accommodate initial run‐off loss amounts based on previous rainfall, slightly enhances model simulation performance; both ENS and R2 increased by 1.4% for total streamflow in a 4‐year calibration period. A continuous SCS CN method‐based hybrid hydrologic model presented in this study is, therefore, potentially significant to improved implementation of long‐term hydrologic applications for spatially distributed rainfall‐run‐off generation and routing, as a relatively simple hydrologic modelling approach for the use of more reliable gridded types of quantitative precipitation estimations. 相似文献
253.
Samuel E. Tuttle Jennifer M. Jacobs Carrie M. Vuyovich Carrie Olheiser Eunsang Cho 《水文研究》2018,32(6):817-829
In the Northern Great Plains, melting snow is a primary driver of spring flooding, but limited knowledge of the magnitude and spatial distribution of snow water equivalent (SWE) hampers flood forecasting. Passive microwave remote sensing has the potential to enhance operational river flow forecasting but is not routinely incorporated in operational flood forecasting. We compare satellite passive microwave estimates from the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR‐E) to the National Oceanic and Atmospheric Administration Office of Water Prediction (OWP) airborne gamma radiation snow survey and U.S. Army Corps of Engineers (USACE) ground snow survey SWE estimates in the Northern Great Plains from 2002 to 2011. AMSR‐E SWE estimates compare favourably with USACE SWE measurements in the low relief, low vegetation study area (mean difference = ?3.8 mm, root mean squared difference [RMSD] = 34.7 mm), but less so with OWP airborne gamma SWE estimates (mean difference = ?9.5 mm, RMSD = 42.7 mm). An error simulation suggests that up to half of the error in the former comparison is potentially due to subpixel scale SWE variability, limiting the maximum achievable RMSD between ground and satellite SWE to approximately 26–33 mm in the Northern Great Plains. The OWP gamma versus AMSR‐E SWE comparison yields larger error than the point‐scale USACE versus AMSR‐E comparison, despite a larger measurement footprint (5–7 km2 vs. a few square centimetres, respectively), suggesting that there are unshared errors between the USACE and OWP gamma SWE data. 相似文献
254.
Young-Gyu Park Kyung-Hee Seol Kyung-On Boo Johan Lee Chunho Cho Young-Hwa Byun Seongbong Seo 《Ocean Science Journal》2018,53(3):437-448
This modeling study investigates the impacts of increasing atmospheric CO2 concentration on acidification in the East Sea. A historical simulation for the past three decades (1980 to 2010) was performed using the Hadley Centre Global Environmental Model (version 2), a coupled climate model with atmospheric, terrestrial and ocean cycles. As the atmospheric CO2 concentration increased, acidification progressed in the surface waters of the marginal sea. The acidification was similar in magnitude to observations and models of acidification in the global ocean. However, in the global ocean, the acidification appears to be due to increased in-situ oceanic CO2 uptake, whereas local processes had stronger effects in the East Sea. pH was lowered by surface warming and by the influx of water with higher dissolved inorganic carbon (DIC) from the northwestern Pacific. Due to the enhanced advection of DIC, the partial pressure of CO2 increased faster than in the overlying air; consequently, the in-situ oceanic uptake of CO2 decreased. 相似文献
255.
To establish viable earthquake counterplans for ports in Korea, data regarding earthquake motion on the ground and in buildings must be collected using acceleration monitoring systems. Acceleration monitoring-based strategies for port facilities are useful not only for ensuring rapid responses during and after earthquakes but also for regional data collection to assist reliable seismic design. Acceleration monitoring systems were installed at coastal facility sites in target ports, including a soil site to represent the facility and a rock site as a reference. The systematic earthquake alert software was designed to help them in decision-making about a possible seismic hazard and its reporting. The earthquake alert system was composed of two sequential functional software systems sharing an acceleration monitoring database applied to the target ports. The earthquake response software system triggers an alarm based on the peak ground acceleration per second computed from the monitored data. Then, the earthquake hazard estimation software system evaluates possible earthquake-induced site-specific geotechnical hazards linked to the peak ground acceleration. The integrated system was successfully operated and was able to rapidly provide an emergency report containing event records and geotechnical earthquake hazards during the September 2016 Gyeongju earthquake, the largest recorded earthquake in Korea. 相似文献
256.
A. O. Benz C. Monstein H. Meyer P. K. Manoharan R. Ramesh A. Altyntsev A. Lara J. Paez K.-S. Cho 《Earth, Moon, and Planets》2009,104(1-4):277-285
Radio spectrometers of the CALLISTO type to observe solar flares have been distributed to nine locations around the globe. The instruments observe automatically, their data is collected every day via internet and stored in a central data base. A public web-interface exists through which data can be browsed and retrieved. The nine instruments form a network called e-CALLISTO. It is still growing in the number of stations, as redundancy is desirable for full 24 h coverage of the solar radio emission in the meter and low decimeter band. The e-CALLISTO system has already proven to be a valuable new tool for monitoring solar activity and for space weather research. 相似文献
257.
Ung San Ahn Dong-Chan Koh Joonghyeok Heo Byong-Wook Cho Taehee Kim Byoung-Woo Yum 《水文研究》2021,35(8):e14316
Volcanic aquifers supply a substantial portion of water resources in many parts of the world, including islands, and their productivity depends strongly on volcanic stratigraphy, which exhibits considerable heterogeneity. We investigated water inflow to lava tube caves formed from numerous basaltic lava flows in the northeastern coastal area of Jeju Island after storm events and monitored relative inflow rates monthly over 1 year to characterize groundwater flow processes in the upper parts of volcanic aquifers, and to evaluate the applicability of the previous hydrogeological models proposed for the island. Considerable water inflow arose shortly after storms from exposed palaeosol layers on the walls of the caves. The monthly monitoring results showed that wall inflow associated with these palaeosol layers is substantial. In both cases, discharge from ceiling drips was much less and more temporally variable compared to wall inflow discharge. Water flowing into the caves was rapidly drained through the floor at all monitoring sites. The lateral extent of the palaeosol layers was identified using drill core logs near the cave and outcrops in the coastal area. Based on these results, we inferred that multiple perched aquifers are formed by low-permeability palaeosol layers between lava flows, which are connected by vertical flows at discontinuities in the palaeosol layer, eventually reaching the basal aquifer. This study revealed the water inflow processes observed in lava tube caves constrained by palaeosol layers, and established a hydrogeological conceptual model incorporating multiple perched aquifers in both coastal and mountainous areas associated with extensive palaeosol layers formed during volcanic hiatuses. This finding would help elucidate recharge, groundwater flow, and contaminant transport processes in many volcanic aquifers that are not adequately represented by the previous models, and contribute to better management of groundwater in those areas. 相似文献
258.
Russell Main Moses Azong Cho Renaud Mathieu Martha M. O’Kennedy Abel Ramoelo Susan Koch 《ISPRS Journal of Photogrammetry and Remote Sensing》2011,66(6):751-761
Quantifying photosynthetic activity at the regional scale can provide important information to resource managers, planners and global ecosystem modelling efforts. With increasing availability of both hyperspectral and narrow band multispectral remote sensing data, new users are faced with a plethora of options when choosing an optical index to relate to their chosen or canopy parameter. The literature base regarding optical indices (particularly chlorophyll indices) is wide ranging and extensive, however it is without much consensus regarding robust indices. The wider spectral community could benefit from studies that apply a variety of published indices to differing sets of species data. The consistency and robustness of 73 published chlorophyll spectral indices have been assessed, using leaf level hyperspectral data collected from three crop species and a variety of savanna tree species. Linear regression between total leaf chlorophyll content and bootstrapping were used to determine the leafpredictive capabilities of the various indices. The indices were then ranked based on the prediction error (the average root mean square error (RMSE)) derived from the bootstrapping process involving 1000 iterative resampling with replacement. The results show two red-edge derivative based indices (red-edge position via linear extrapolation index and the modified red-edge inflection point index) as the most consistent and robust, and that the majority of the top performing indices (in spite of species variability) were simple ratio or normalised difference indices that are based on off-chlorophyll absorption centre wavebands (690–730 nm). 相似文献
259.
介绍了简单而又新颖的公式,使用微震的二分量,即圆形台阵记录的水平运动直接推断勒夫波相速度(cL)时,这些公式具有帮助作用。我们的公式与一般用于推断瑞雷波相速度(cR)的微震探测技术的空间自相关(SPAC)方法的公式类似。虽然SPAC方法现有的理论确实提供了估计cL的可能性,但这只能通过求解非线性的方程组才能实现,而其中待求解的未知数也包括cR以及瑞雷波?勒夫波的幂分配比。相反,在我们公式中cL是出现的唯一未知数。基于我们推荐公式——我们称为SPAC+L、SPAC-L和CCA-L(其中CCA表示无中心圆形台阵)法——的cL估算法的现场适用范围通过2个测试点的分析结果说明。在所提出的3种技术中,SPAC+L法由于表现最佳而出名。3种方法的有效波长范围下限是台阵半径r的2~5倍区域,上限是10~25r的区域。近年来,提出了类似的仅涉及cL的圆形台阵微震技术,但与它们相比,我们在此给出的方法,不是在数理计算上繁冗更少,就是在数学上更为简单。 相似文献
260.
Ara Cho Daekyo Cheong Jin Cheul Kim Dong-Yoon Yang Jin-Young Lee Kaoru Kashima Kota Katsuki 《Journal of Paleolimnology》2018,60(4):553-570
Hwajinpo is the largest lagoon in Korea and is located along the east coast of the country. It possesses Holocene sediments that provide an important record of past climate change. We studied the evolution of Hwajinpo Lagoon using grain size data and diatom assemblages in an 11.0-m core (HJ02), which was obtained at the mouth of a small river that drains into the lagoon. Core chronology was established with accelerator mass spectrometry 14C dates and optically stimulated luminescence dates. Diatom assemblages and grain size analysis revealed that estuarine conditions in the inner lagoon area transitioned to an open embayment ca. 8 ka as a result of sea-level rise. Around 7.8 ka, the open bay became a semi-closed bay as a consequence of development of a sand barrier. After the bay was semi-closed, marine water inflow was increasingly restricted as the sand barrier developed, and the semi-closed bay became a completely enclosed, low-salinity, brackish lagoon around 6 ka. There was an erosional hiatus between 5.5 and 1.7 ka (7.0 m depth), likely caused by river flooding and a switch in the location of drainage along the delta. The lagoon became oligohaline around 1.6 ka, likely because of increasing precipitation associated with an intensified Asian summer monsoon. This increase in precipitation resulted in expansion of the sand bar by sediment inflow, driven by agricultural development in the area. About 1000 years ago, the diatom assemblage was similar to the modern assemblage, suggesting the lagoon’s current geomorphic conditions had been established. 相似文献