Distribution and expression of gas seeps in a gas hydrate province of the northeastern Sakhalin continental slope, Sea of Okhotsk   总被引：1，自引：0，他引：1  

Young Keun Jin  Young-Gyun Kim  Boris Baranov  Hitoshi Shoji  Anatoly Obzhirov 《Marine and Petroleum Geology》2011,28(10):1844-1855

Multidisciplinary surveys were conducted to investigate gas seepage and gas hydrate accumulation on the northeastern Sakhalin continental slope (NESS), Sea of Okhotsk, during joint Korean–Russian–Japanese expeditions conducted from 2003 to 2007 (CHAOS and SSGH projects). One hundred sixty-one gas seeps were detected in a 2000 km² area of the NESS (between 53°45′N and 54°45′N). Active gas seeps in a gas hydrate province on the NESS were evident from features in the water column, on the seafloor, and in the subsurface: well-defined hydroacoustic anomalies (gas flares), side-scan sonar structures with high backscatter intensity (seepage structures), bathymetric structures (pockmarks and mounds), gas- and gas-hydrate-related seismic features (bottom-simulating reflectors, gas chimneys, high-amplitude reflectors, and acoustic blanking), high methane concentrations in seawater, and gas hydrates in sediment near the seafloor. These expressions were generally spatially related; a gas flare would be associated with a seepage structure (mound), below which a gas chimney was present. The spatial distribution of gas seeps on the NESS is controlled by four types of geological structures: faults, the shelf break, seafloor canyons, and submarine slides. Gas chimneys that produced enhanced reflection on high-resolution seismic profiles are interpreted as active pathways for upward gas migration to the seafloor. The chimneys and gas flares are good indicators of active seepage.  相似文献   

Empirical ocean-color algorithms to retrieve chlorophyll-a, total suspended matter, and colored dissolved organic matter absorption coefficient in the Yellow and East China Seas   总被引：4，自引：1，他引：3  

Eko Siswanto  Junwu Tang  Hisashi Yamaguchi  Yu-Hwan Ahn  Joji Ishizaka  Sinjae Yoo  Sang-Woo Kim  Yoko Kiyomoto  Keiko Yamada  Connie Chiang  Hiroshi Kawamura 《Journal of Oceanography》2011,67(5):627-650

A bio-optical dataset collected during the 1998?C2007 period in the Yellow and East China Seas (YECS) was used to provide alternative empirical ocean-color algorithms in the retrieval of chlorophyll-a (Chl-a), total suspended matter (TSM), and colored dissolved organic matter (CDOM) absorption coefficients at 440 nm (ag₄₄₀). Assuming that remote-sensing reflectance (Rrs) could be retrieved accurately, empirical algorithms for T_Chl (regionally tuned Tassan??s Chl-a algorithm) in case-1 waters (T_Chl2i in case-2 waters), T_TSM (regionally tuned Tassan??s TSM algorithm), and T_ag440 or C_ag440 (regionally tuned Tassan??s or Carder??s ag₄₄₀ algorithm) were able to retrieve Chl-a, TSM, and ag₄₄₀ with uncertainties as high as 35, 46, and 35%, respectively. Applying the standard SeaWiFS Rrs, T_Chl was not viable in the eastern part of the YECS, which was associated with an inaccurate SeaWiFS Rrs retrieval because of improper atmospheric correction. T_Chl behaved better than other algorithms in the turbid case-2 waters, although overestimation was still observed. To retrieve more reliable Chl-a estimates with standard SeaWiFS Rrs in turbid water (a proxy for case-2 waters), we modified T_Chl for data with SeaWiFS normalized water-leaving radiance at 555 nm (nLw₅₅₅) > 2 mW cm^?2 ??m^?1 sr^?1 (T_Chl2s). Finally, with standard SeaWiFS Rrs, we recommend switching algorithms from T_Chl2s (for case-2 waters) to MOC_Chl (SeaWiFS-modified NASA OC4v4 standard algorithm for case-1 waters) for retrieving Chl-a, which resulted in uncertainties as high as 49%. To retrieve TSM and ag₄₄₀ using SeaWiFS Rrs, we recommend empirical algorithms for T_TSM (pre-SeaWiFS-modified form) and MT_ag440 or MC_ag440 (SeaWiFS Rrs-modified forms of T_ag440 or C_ag440). These could retrieve with uncertainties as high as 82 and 52%, respectively.  相似文献   

Tracing origins of sewage and organic matter using dissolved sterols in Masan and Haengam Bay,Korea     

Hyo Jin Lee  Sang Hee Hong  Moonkoo Kim  Sung Yong Ha  Soon Mo An  Won Joon Shim 《Ocean Science Journal》2011,46(2):95-103

Masan and Haengam Bays in Korea are highly polluted and semi-enclosed. Domestic and industrial effluents are directly or indirectly discharged into the bays through sewage treatment plants (STP) and creeks. In this study, 15 dissolved sterol compounds were determined in order to understand their sources and relative contribution. Freshwater samples were taken from 13 creeks and at two STP sites on a monthly basis. Total dissolved sterol concentrations ranged from 993 to 4158 ng/L. The concentrations of sterols in winter were higher than in summer. Among the sterols analyzed, cholesterol, β-sitosterol, coprostanol and cholestanone were major compounds in creek water. Seawater samples were concurrently collected at 21 stations in Masan Bay. Total sterol concentrations ranged 118–6,956 ng/L. Inner bay showed high concentrations of sterols in summer, while outer bay showed high sterol concentrations in winter. Among the sterols, cholesterol, β-sitosterol and brassicasterol were major compounds in seawater. In order to examine the contribution of urban sewage, the concentration of coprostanol and fecal sterol ratios were calculated. Most of the creek water, inner bay and near STP outlet samples were affected by sewage. Terrestrial organic matters accounted for a high proportion of dissolved organic matter origin. Fecal origins were relatively high in the inner bay areas and in the STP outlet, while sterols of marine origin were high in the outer bay areas.  相似文献   

<Emphasis Type="Italic">Cochlodinium polykrikoides</Emphasis> red tide detection in the South Sea of Korea using spectral classification of MODIS data     

Young Baek Son  Joji Ishizaka  Jong-Chul Jeong  Hyun-Choel Kim  Taehee Lee 《Ocean Science Journal》2011,46(4):239-263

To distinguish true red tide water (particularly Cochlodinium polykrikoides blooms) from non-red tide water (false satellite high chlorophyll water) in the South Sea of Korea, we developed a systematic classification method using spectral information from MODIS level products and applied it to five different harmful algal bloom events. Red tide and nonred tide waters were classified based on four different criteria. The first step revealed that the radiance peaks of potential red tide water occurred at 555 and 678 nm. The second step separated optically different waters that were influenced by relatively low and high contributions of colored dissolved organic matter (CDOM) (including detritus) to chlorophyll. The third and fourth steps discriminated red tide water from non-red tide water based on the blue-to-green ratio in areas with lower and higher contributions of CDOM to chlorophyll, respectively. After applying the red tide classification (using the four criteria), the spectral response of the red tide water, which is influenced by pigment concentration, showed different slopes for the blue and green bands (lower slope at blue bands and higher slope at green bands). The opposite result was found for non-red tide water, due to decreasing phytoplankton absorption and increasing detritus/CDOM absorption at blue bands. The results were well matched with the discoloration of water (blue to dark red/brown) and delineated the areal coverage of C. polykrikoides blooms, revealing the nature of spatial and temporal variations in red tides. This simple spectral classification method led to increase user accuracy for C. polykrikoides and non-red tide blooms (>46% and >97%) and provided a more reliable and robust identification of red tides over a wide range of oceanic environments than was possible using chlorophyll a concentration, chlorophyll anomaly, fluorescence analysis, or proposed red tide detection algorithms.  相似文献   

Comment on ‘Clinoform quantification for assessing the effects of external forcing on continental margin development’     

Andrew L. Petter  Wonsuck Kim  Tetsuji Muto  Ronald J. Steel 《Basin Research》2011,23(1):118-121

The application of geometric modeling to shelf‐margin stratigraphy has the potential to constrain interpretations of external forcings on margin development. Here we apply such a model to the Ebro margin in order to complement the analysis of Kertznus & Kneller (2009) . Our results suggest that increased mass wasting in the Pleistocene was unlikely to have been a factor in the observed long‐term shelf‐edge trajectory, and that the trajectory can be explained by the interaction of sediment flux, relative sea‐level rise, and basin shape.  相似文献   

The 27 July 2011 debris flows at Umyeonsan,Seoul, Korea   总被引：1，自引：1，他引：0  

Sangseom Jeong  Yongmin Kim  Joon Kyu Lee  Junghwan Kim 《Landslides》2015,12(4):799-813

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A biogeochemical orientation survey in the Moisan gold-mineralized area, Haenam district in Korea     

Ji-Eun Jung  Jong-Nam Kim  Hyo-Taek Chon 《Journal of Geochemical Exploration》2011,111(3):152-159

A biogeochemical orientation survey was carried out in the vicinity of an epithermal Au deposit in the Moisan Au–Ag mineralized area, Haenam district in Korea. The Au–Ag bearing quartz veins of the mine occur as narrow open-space fillings within Cretaceous silicic pyroclastics. The vein minerals consist mainly of quartz, sericite, pyrite, chalcopyrite, and galena, with some electrum and argentite. The main objectives of this study were to study the geochemical characteristics of rocks, soils and plants in this area, to investigate the spatial relationship between Au and associated elements in rock–soil–plant system, and to evaluate the applicability of biogeochemical prospecting for Au vein occurrences in Korea. Samples of rocks and soils, and leaves of three plant species (Japanese red pine — P. densiflora, oriental white oak — Q. aliena, Japanese mallotus — M. japonicus) were collected from the target mineralized area and control barren locations, and analyzed for trace elements by instrumental neutron activation analysis. Sampling lines were composed of one slope line which is almost parallel to the mineralized quartz-veins, and four transect lines spaced 100 m apart across the veins at 20 m sampling intervals. From the multi-element data of rock samples (n = 9), high values of Au (maximum 2030 ppb) are spatially related to Au–quartz veins. Soil samples (n = 61) collected from five sampling lines show higher values of Au (24–825 ppb) whereas soil samples from the control locations have lower values of Au (below 25 ppb). Many plant species collected from the vicinity of the veins have high Au contents compared with those at the control locations, but the ranges of Au values are variable among plant species. In a total of 128 samples of plant leaves, Q. aliena yielded Au values of 0.4 to 6.9 ppb, and M. japonicus 0.9 to 4.1 ppb. Gold contents in P. densiflora ranged from 0.1 to 5.6 ppb. Plant leaves from control areas show less than 1.6 ppb Au. The biological absorption coefficient (BAC) of Au in plants decreases in the order of Q. aliena > M. japonicus > P. densiflora. Based on the results of the study, Q. aliena appeared to be the best sampling media for biogeochemical prospecting of Au in the study area.  相似文献   

Effect of stress history on CPT and DMT results in sand     

Moon-Joo Lee  Sung-Kun Choi  Min-Tae Kim  Woojin Lee 《Engineering Geology》2011,117(3-4):259-265

In order to investigate the effect of stress history on in-situ test results in granular sediments, a series of CPTs and DMTs are performed on Busan sand prepared in the calibration chamber. K_D is found to be the most sensitive to the stress history among CPT and DMT measurements. E_D and q_c are observed to be similarly affected by the stress history and, therefore, the E_D–q_c relation appears to be almost independent of the stress history. The K_D–D_R relation established without considering the stress history is likely to overestimate the relative density of OC sand. It is shown that the existence of the pre-stress of the granular sediment can be indirectly recognized by an estimation of the relative density larger than 100% when using the K_D–σ_v′–D_R relation suggested for NC sand. Although q_c/σ_v′–K_D/K₀ and E_D/σ_v′–K_D/K₀ relations are heavily influenced by the stress history, q_c/σ_m′–K_D/K₀ and E_D/σ_m′–K_D/K₀ relations are observed to be independent of the stress history. Based on these relations, charts to evaluate the K₀ value from q_c and/or DMT indices are developed for both NC and OC sands. The design chart based on E_D/σ_m′–K_D/K₀ and E_D/σ_v′–K_D/K₀ relations is expected to be practically useful as the usage of this chart requires only DMT indices. The developed design charts are applicable to Busan sand but different sets of equations and charts may be developed for other sands.  相似文献   

A DEM-based evaluation of potential flood risk to enhance decision support system for safe evacuation   总被引：2，自引：1，他引：1  

Jinyoung Kim  Yuji Kuwahara  Manish Kumar 《Natural Hazards》2011,59(3):1561-1572

A practical, DEM-based practical method is proposed to enhance flood risk management in fluvial areas by quantifying relative risk as a function of vulnerability to inland and evacuation difficulty. Both measures are based mainly on the topography of the region, so the method does not require detailed data on the physical characteristics of the land. First, we use the deterministic 8-node method on a digital elevation map (DEM) to trace storm waterways. Second, we repeat the process on a reversed DEM to trace evacuation routes that avoid the waterways and zones dangerously close to the rivers. Finally, on the basis of such two flow lines of evacuee and storm water, we proposed the protocol to evaluate the flood risk at every point on the map taking into account both the minimum time required for floodwater to arrive and duration of an evacuation from that location. The time that must be allocated for safe evacuation is defined as the potential flood risk of evacuation (PFRE). The method is demonstrated on a fluvial area of the Kaki River in Nagaoka city, Japan. In addition, we illustrated the application of the PFRE map to divide the region into areas of greater or lesser evacuation urgency.  相似文献   

Representation of tropical storms in the northwestern pacific by the Modern-Era Retrospective analysis for research and applications     

Myong-In Lee  Siegfried D. Schubert  Dongmin Kim 《Asia-Pacific Journal of Atmospheric Sciences》2011,47(3):245-253

This study examines the tropical storms simulated in the Modern-Era Retrospective analysis for Research and Applications (MERRA) global atmospheric reanalysis for the recent 12 years (1998–2009), focusing on the tropical storm activity over the Northwestern Pacific. For validation, the International Best Track Archive for Climate Stewardship (IBTrACS) dataset is used as an observational counterpart. Climatological-mean features of the tropical storm genesis, tracks and their maximum intensity are the primary interests in this study. Regarding the genesis location of tropical storms, MERRA is reasonable in resolving major development regions over the South China Sea and the Northwestern Pacific close to the Philippines. The seasonal variation of the number of storms is also reproduced in a realistic way in MERRA, with peak values occurring from July to September. In addition, MERRA tends to reproduce the observed interannual variation of the number of tropical storms during the 12-years, though with a limited accuracy. The simulated paths toward higher latitudes are also reasonable in MERRA, where the reanalysis corresponds well with the observations in resolving frequent paths of westward moving storms and recurving storms toward the northeast. Regarding the intensity, MERRA captures the linear relationship between the minimum center pressure and the maximum wind speed near the surface at the maximum development. Some discrepancies from the observed features are found in the reanalysis, such as less frequent development of storms over the South China Sea and less frequent paths over this region. The reanalysis also does not attain the observed maximum intensity for the resolved tropical storms, particularly underestimating the center pressure. These deficiencies are likely related to limitations in the horizontal resolution and the parameterized physics of the data assimilation system.  相似文献