Presence of high nitrate to phosphate ratio subsurface water in the Tsushima Strait during summer

To identify water with an excess nitrate concentration to phosphate ratio and its potential source, the nutrient concentrations in the Tsushima Strait (TSS) were investigated over ten cruises in August and September 2007–2014, excluding 2010. On the basis of the Redfield ratio, water with an excess nitrate concentration of >1 μM (positive ExNOx water) was identified below the surface mixed layer during four cruises in 2011–2013. Positive ExNOx water was present mainly in less-saline (<34) waters with a density of 22–25 σ _θ , and 25–75 m depth. However, in August 2012, positive ExNOx was detected in dense (25–25.5 σ _θ ) and deep (50–110 m depth) waters near the salinity maximum, although the salinity during this period was significantly lower than that in other years. The horizontal length of positive ExNOx water was >100 km across the TSS during two cruises in August 2012 and September 2013, respectively. According to multi-regression analysis conducted on the silicate concentration, temperature, and salinity, the silicate concentration was increased in the less-saline subsurface water. The required amount of original freshwater was 10^8–9 m³ day^?1 based on the excess nitrate concentration. This evidence indicates that the positive ExNOx water originated from large river waters such as the Changjiang. Thus, discharged water from the rivers of the East Asia is contributing to the increased N:P ratio in the Tsushima Warm Current, southern Japan Sea.     

Decline in radiocesium in seafloor sediments off Fukushima and nearby prefectures

Radioactivity has been monitored in seafloor sediments off Fukushima and nearby prefectures regularly. During the initial monitoring period (May–September 2011), ¹³⁷Cs concentrations in the surface sediments (0–3 cm) generally increased to 8–580 Bq/kg. Subsequently, concentrations decreased at variable rates. In the latest data, from February 2016, concentrations were still higher at 0.8–141 Bq/kg than the pre-accident level. The geometric mean concentration declined steadily from 47 Bq/kg in September 2011 to 13 Bq/kg in February 2016. The ¹³⁷Cs abundance (Bq/m²) in the surface sediment at each station decreased similarly. The rate of decrease of surface abundance varied spatially by almost one order of magnitude, ranging from 1.1 × 10^?4 to 1.7 × 10^?3/day, equivalent to halving times of 16–1.1 years, respectively. The rate of decrease was related to the median sediment grain size at each station. In addition, bottom-water dynamics, through the redistribution of bottom sediments, may have caused spatial variability in the rate of decrease, whereas vertical profiles of ¹³⁷Cs concentrations in the sediment suggest that vertical migration of ¹³⁷Cs was not a major mechanism reducing the surface ¹³⁷Cs concentration. From September 2011 to February 2016, the overall halving time of ¹³⁷Cs in the surface sediment in the monitoring area, excluding the area inside a 30-km radius from the Fukushima Dai-ichi Nuclear Power Plant, was 2.3 years. Thus, 76% of the originally deposited ¹³⁷Cs (46 × 10¹² Bq) in the surface sediment was transported out of the area during that period.     

The ultra-low-frequency magnetic disturbances associated with earthquakes

The ultra-low-frequency (ULF) electromagnetic emission is recently recognized as one of the most promising candidates for short-term earthquake (EQ) prediction. This paper reviews previous convincing evidence on the presence of ULF emissions before three major EQs. Then, we present further statistical study on the ULF occurrence, our networks of ULF monitoring in different spatial scales in Japan and finally we present several signal processings to identify the seismogenic emissions by showing latest results for recent large EQs.     

冲绳海槽海底热液喷出口附近海水中~(210)Pb和~(210)Po的行为

讨论了在冲绳海槽伊平屋海岭和南奄西海丘两处海底热液喷出口附近海水中的铀系子体放射性核素2 10 Pb和2 10 Po浓度的垂直分布剖面 .在伊平屋海岭 ,甲烷及2 2 2 Rn的数据表明海底热液活动不强 ,总2 10 Pb和2 10 Po放射性均低于它们各自母体的放射性 ,2 10 Pb和2 10 Po在海水中的平均停留时间分别为 2 0和 2～ 5a ,而在以“黑色烟雾”为特征的海底热液活动强烈的南奄西海丘 ,在”烟雾”中的总2 10 Pb含量 ( 0 1 6 7× 1 0 -3～ 2 50× 1 0 -3Bq/kg)相对其母体2 2 6Ra贫乏 ,而总2 10 Po含量 ( 1 83× 1 0 -3～ 2 83×1 0 -3Bq/kg)则相对其母体2 10 Pb过剩 .该处海水中的2 10 Po的放射性高于东海陆架区及冲绳海槽其他海区 ,并且显示了2 10 Po过剩 .2 10 Pb/ 2 2 6Ra以及2 10 Po/ 2 10 Pb放射性比值的范围分别为 0 1～ 0 4和 1 1～ 7 8.在热液扩散带中2 10 Pb被优先从海水中清除 .控制南奄西海丘海水中2 10 Pb浓度的可能机制涉及到2 10 Pb通过扩散作用的横向输送 .在热液扩散带中高2 10 Po/ 2 10 Pb放射性比值表明2 10 Pb的耗尽及2 10 Po从海底热液喷出口的加入 .     

冲绳海槽海底热液喷出口附近海水中210Pb和210Po的行为

讨论了在冲绳海槽伊平屋海岭和南奄西海丘两处海底热液喷出口附近海水中的铀系子体放射性核素210Pb和210Po浓度的垂直分布剖面.在伊平屋海岭,甲烷及222Rn的数据表明海底热液活动不强,总210Pb和210Po放射性均低于它们各自母体的放射性,210Pb和210Po在海水中的平均停留时间分别为20和2～5a,而在以“黑色烟雾”为特征的海底热液活动强烈的南奄西海丘,在”烟雾”中的总210Pb含量(0.167×10-3～2.50×10-3Bq/kg)相对其母体226Ra贫乏,而总210Po含量(1.83×10-3～2.83×10-3Bq/kg)则相对其母体210Pb过剩.该处海水中的210Po的放射性高于东海陆架区及冲绳海槽其他海区,并且显示了210Po过剩.210Pb/226Ra以及210Po/210Pb放射性比值的范围分别为0.1～0.4和1.1～7.8.在热液扩散带中210Pb被优先从海水中清除.控制南奄西海丘海水中210Pb浓度的可能机制涉及到210Pb通过扩散作用的横向输送.在热液扩散带中高210Po/210Pb放射性比值表明210Pb的耗尽及210Po从海底热液喷出口的加入.     

234 Th示踪法测定北太平洋西北海域冬季真光层中颗粒态有机碳输出通量

讨论了1997年冬季在北太平洋西北海域7个站位的表层至200m水深水柱中溶解及颗粒态234Th,颗粒态有机碳(POC)、氮(PON)及叶绿素a浓度的垂直分布剖面.溶解态、颗粒态及总的234Th的放射性在真光层中显著低于母体238U的放射性,总的234Th放射性在水深大于100m时趋于平衡.利用234Th-238U在海洋表层海水中的放射性不平衡推导出了北太平洋西北海域冬季真光层海水中234Th的平均停留时间和输出通量以及颗粒态有机碳和有机氮的输出通量.在亚北极环流区溶解态234Th的停留时间为40~50d,而在黑潮-亲潮共同影响区为20d左右.颗粒态有机碳和有机氮从真光层的输出通量范围分别为3.8~8.2和0.50~0.98mmol/(m2·d),西部海区高于东部海区,南部海区高于北部海区.在黑潮-亲潮共同影响区较高的颗粒态有机碳输出通量表明光照量及陆源营养盐物质的提供是两个决定生产力的主要因素.叶绿素a的水深分布和POC/PON的值同Redfield的比值的一致性表明这个海区的冬季颗粒物主要由浮游植物构成.北太平洋西北海域在冬季的颗粒有机碳输出通量可高于世界大洋一些海区春、夏季的颗粒有机碳输出通量.     

Rheological contrast between garnet and clinopyroxene in the mantle wedge: An example from Higashi-akaishi peridotite mass,SW Japan

Garnet clinopyroxenites occur within foliated dunite in the Higashi-akaishi peridotite mass, located within the subduction-type high-pressure/low-temperature Sanbagawa metamorphic belt. The garnet clinopyroxenites contain 3–80% garnet, and garnet and clinopyroxene are homogeneously distributed. Garnet crystals contain extensive, regular dislocation arrays and dislocation networks, suggesting that dislocation creep was the dominant deformation mechanism. Analyses of crystallographic orientation maps indicate similar grain sizes and aspect ratios for garnet and clinopyroxene, regardless of modal composition, indicating that these minerals deformed with similar degree of plasticity. Moreover, indexes of crystallographic fabric intensity (i.e., J-index and M-index) for both garnet and clinopyroxene tend to increase with increasing modal composition of garnet. Fourier-transform infrared spectroscopy analysis revealed that water content in garnet is ～60 ppm, whereas that in clinopyroxene is ～70 ppm. Olivine crystal-preferred orientations in the Higashi-akaishi peridotite mass, characterized by [0 0 1] (0 1 0), are thought to have developed during deformation under wet conditions. Consequently, we argue that the presence of water could act to enhance garnet plasticity during deformation. The results reveal contrasting influences of water on the deformation of garnet and diopside: under wet conditions compared with dry, the strain rate increases by two orders of magnitude for garnet but by an order of magnitude for diopside. Given the influence of water on the creep strength of garnet, garnet within the Higashi-akaishi mass may have become significantly as weak as clinopyroxene during deformation.     

对“评‘两次希腊大地震的预测’”的答复

我们欢迎来自Papadopoulos的批评。但我们必须指出,这些批评大部分都是不正确的。     

A NUMERICAL STUDY ON THE FORMATION AND DEVELOPMENT OF ISLAND-INDUCED CYCLONE AND ITS IMPACT ON TYPHOON STRUCTURE CHANGE AND MOTION

In this paper,the impact of the Taiwan Island topography on the structure change and motion ofTyphoon Dot(9017)during its crossing the Taiwan Island is studied with a modified version of aJMA operational regional model(Japan spectral model,JSM).A series of sensitivity experiments areconducted to detect the forming and developing mechanism of an island-induced cyclone.Results showthat lee side low pressure center plays a very important role in the formation of the induced-cyclonewhile a typhoon is approaching a large island with high mountains.The position and intensity of theinduced cyclone is sensitive to the height and location of island mountain,intensity of TC and under-lying surface topography distribution as well.A preliminary formation criterion of the island-inducedcyclone is obtained.     

东海与黑潮海水中宇宙射线成因核素10Be的研究

讨论了中日东海MASFLEX合作计划中调查的东海及冲绳海槽海水中溶解态10Be浓度水平及垂直剖面的结果，在这个海区，影响10Be浓度的因素主要有生物生产力，悬浮颗粒物的再溶解，以及长江水与黑潮水的混合程度。在样品采集期间（夏季和秋季），东海水柱呈分层状态，通常10Be的垂直剖面可以分成三层，即表面混合层，10Be释放层和底层，表层水10Be的浓度众长江口到黑潮逐渐增大，在黑潮的边缘则剧烈增大，10Be的垂直分布表明，在夏季10Be富集在长江口附近和大陆架中部的底层水中，这两个富集海区是分开的，很可能是由大陆沿岸水所隔开，在秋季，10Be在底层水中的富集仅仅出现在东海大陆架的西部，这个现象是和受季风影响的东海海流的变化相一致的，黑潮分支在台湾东北外海向东海南部侵入对10Be的影响要比黑潮主干流本身更加重要显著，由箱式模型所得到的10Be质量平衡计算结果表明，来自黑潮的10Be输入要比长江及大气沉降的输入更为重要，输入东海的10Be大约81％进入到沉积物中，而19％的10Be则通过海流和水交换流出东海，在东海的10Be沉积通量是10Be全球平均大气生产率的5倍左右，因而东海是10Be的一个重要汇集地。