Stratigraphic Sequence and Sedimentary Systems in the Middle-Southern Continental Slope of the East China Sea from Seismic Reflection Data: Exploration Prospects of Gas Hydrate

Many evidences for gas hydrate bearing sediments had been found in the continental slope of the East China Sea,such as bottom simulating reflections(BSRs),undersea gas springs,pyrite associated with methane leakage,mud diapirs/mud volcanos,bottom-water methane anomalies and so on.In this study,six key stratigraphic interfaces including T_0(seafloor),T_1(LGM,23 kyr B.P.),T_2(2.58 Myr),T_3(5.33 Myr),T_4(11.02 Myr)and T_5(16.12 Myr)were identified,and then five third-order sequences of SQIII1 to SQIII5 were divided.However,T5 in southern continental slope is not found,which shows that the middle-northern Okinawa Trough had begun to rift in the early Miocene,earlier than the southern segment.Four system tracts including lowstand systems tract(LST),transgressive systems tract(TST),highstand systems tract(HST)and falling stage systems tract(FSST)are further divided.The marine erosion interface of 11.02 Myr and regressive unconformity interface of 23 kyr B.P.indicate two large-scale sea level drop events in the research area.Seven typical seismic facies identified in the continental slope are continental shelf-edge deltas,littoral fluvial-delta plains,incised channels or submarine canyons,slope fans,submarine fans or coastal sandbars,littoral-neritic finegrained sediments,mud volcanos and some other geological bodies respectively.The minimum water depth for hydrate occurrence in the Okinawa Trough is 630 m,and the thickness of gas hydrate stability zone in continental slope is between 0 and 590 m.The calculated bottom boundary of hydrate stability zone is slightly deeper than BSRs on the seismic sections.The re-depositional turbidite sand bodies,such as canyon channels,slope fans and submarine fans developed in Quaternary strata,are the predominant hydrate reservoirs.According to developing process,the dynamic accumulation of hydrate systems can be divided into three evolutionary stages including canyon erosion and hydrate stability zone migration stage,sediments destabilizing and methane leakage stage,and channel filling and hydrate re-occurrence stage.

Effect of sea surface temperature during critical early life history stages of Portunus trituberculatus on later yield

The early life stages of marine organisms are pivotal in shaping community dynamics and resource availability.In this study,we focused on Portunus trituberculatus,a crustacean integral to China's fisheries economy,and examined the effect of sea surface temperature(SST)in its critical early life stages on subsequent yields.To analyze the correlation between SST in different larval stages and the corresponding yield of P.trituberculatus,we simulated the transport and distribution of larvae from 2014 to 2022 by employing circulation models and Lagrangian particle tracking experiments(LPTE).In the five years(2014,2015,2016,2019,and 2020),particles were transported in a northwestern direction and moved in the direction of low SST.The distribution of particles in the megalopa stage(M stage)were located in the region of the lower temperature.In 2017,2018,and 2021,the particles were transported in a northeastern direction but they did not move with the gradient of low SST in these years,and the particles in the last M stage were located in the region where the SST was at the peak of the time period.In 2022,the distribution was observed for most of the particles in the southwestern part of Zhejiang coast,a small part of them were transported in the northwestern direction and a small amount of particles was distributed offshore along the northern area of the Zhejiang coast.The correlations between the SST at each stage of larvae with the corresponding year's yield showed that the yield of P.trituberculatus decreased significantly(R=-0.772,P=0.015)with increasing SST at the M stage.This study preliminarily explains the correlation between SST at the larval stage and the yield of P.trituberculatus and provides essential information for scientific stock enhancement in the future.

Fishery biology of whitespotted conger Conger myriaster(Brevoort, 1856) in the Yellow Sea and East China Sea

Whitespotted conger Conger myriaster is a commercially important species in the seas around China, Korea and Japan. The coastal waters of China serve as an important feeding ground for congers, but the spatio-temporal variations in the fishery and biological characteristics of the population have been rarely evaluated and less well understood in this area. We studied the growth, spawning and feeding characteristics of C. myriaster on the basis of samples collected from October 2016 to April 2017 in the Yellow Sea and East China Sea. A total of 529 specimens were collected, with ages ranging from 1 to 6 years and total length ranging from 132 mm to 834 mm. The parameters of von Bertalanffy growth equation L∞ and k were 1 026 mm and 0.226 a^–1, respectively;the sex ratio was 88:0 (female: male) in the East China Sea and 2.67:1 in the South Yellow Sea;the development stage of ovary ranged from peri-nucleolus stage to secondary yolk globule stage, and the testis of two males was at midmeiotic stage;Crustacean was the major prey for conger of small length, and food source shift to fish with somatic growth. The results showed substantial differences from previous studies in Japan and Korean waters, as well as from China seas in the 1980s, suggesting potential spatiotemporal changes in the biological characteristics of C. myriaster. This study may improve current understanding of the fishery biology of C. myriaster in the Yellow Sea and East China Sea.

Research progress and challenges of natural gas hydrate resource evaluation in the South China Sea

As an efficient clean energy,natural gas hydrate(NGH)has become a hot topic in recent researches.Since1990 s,China has made great achievements and progress in NGH exploration in the South China Sea(SCS),including determination of the favorable distribution areas and favorable strata thickness,identification of the dual source for accumulation,evaluation of the prospective gas contents,verification of the widespread existence,and confirmation of the technical recoverability of NGH resources.However,there are three major challenges in the NGH studies.First,all the 24 national key and major projects in the SCS focused on trial production engineering and geological engineering in the past 20 years,while 8 of the 10 international NGH research projects focused on resource potential.Second,resource evaluation methods are outdated and some parameter selection are subjective.Third,the existing resource evaluation results are low-level with a great uncertainty,and cannot be used to guide NGH exploration and production or strategic research.To improve the evaluation of NGH resources in the SCS,future researches should focus on four aspects:(1)improve the research on the criterion of the objective existence of NGH and the method of prediction and evaluation;(2)apply new theories and methods from the global NGH research;(3)boost the research on the difference and correlation of the conditions of hydrocarbon migration and accumulation in different basins;(4)innovate the theory and method of NGH resource potential evaluation.

Distribution and Characteristics of Hazardous Geological Features in the Marine Coastal and Offshore Areas of Zhejiang Province, East China Sea

Newly acquired high-resolution shallow seismic profiles(7069 km in length) in the coastal and offshore areas of Zhejiang Province, East China Sea, China, have revealed eight marine hazardous geological features: shallow gas, sand ridges, erosion ditches, scarps, irregular bedrock features, underwater shoals, buried paleo-channels, and submarine deltas. Based on the seismic profiles, we have constructed a marine geological map of these hazardous features. Shallow gas accumulations are common and occur mainly in two separate nearshore regions that cover 4613 and 3382 km^2 respectively. There are also scattered shallow gas accumulations in the offshore area, typically accompanied by paleo-channels that occur mainly in the middle of the study area. Sand ridges, erosion ditches, scarps, and irregular bedrock features are found mainly in the northeast of the study area in association with each other. In the southeastern part of the study area, the sand ridges have a linear form and trend NW–SE, representing the western part of the linear sand ridges in the East China Sea. The maximum slope gradient is 1?, which suggests that this area is prone to landslides. These hazardous marine geological features are important to marine and engineering activities in this region.

南海东部次海盆下地壳倾斜反射体结构特征及成因

南海东部次海盆洋壳内发育了大量强振幅的壳内倾斜反射体,它记录了海盆洋壳增生过程,深入研究海盆下地壳倾斜反射体的结构及成因,对认识南海海盆扩张过程具有重要意义。本文基于深反射多道地震剖面,刻画了东部次海盆下地壳倾斜反射体的结构特征及内部变形,初步探讨了其发育成因。研究表明,东部次海盆南、北部都发育强振幅的下地壳倾斜反射体,倾斜反射体大部分终止于Moho反射界面,但南北部倾斜反射体的分布范围、结构特征及成因存在明显差异。东部次海盆下地壳倾斜反射体倾斜长度北长南短,北长约15~22 km,南长约5~8 km;分布范围北大南小,北部南北向长约150 km,南部南北向长约70 km。下地壳倾斜反射区的Moho面埋深起伏差异明显北小南大,北为0.5 s,南有1.2 s。基底北部平坦南部起伏大,洋壳厚度北部厚南部薄,推测东部次海盆洋壳增生过程是非对称性和非均一的。东部次海盆下地壳倾斜反射体的成因可能与同岩浆断裂、水热循环、壳幔过渡区岩浆间隙侵入和基底深大断裂密切相关。

Physical Mechanism of Formation of the Bimodal Structure in the Meiyu Front System

The bimodal structure of the Meiyu front system is readdressed after Zhou et al.（2005）. The physical mechanism of the formation of the bimodal distribution is discussed. The bimodal structure of the Melyu front system considerably results from atmospheric moisture gradients, though atmospheric temperature gradients are also not negligible. According to the definition of equivalent potential temperature, and by scale analysis, we find that atmospheric equivalent potential temperature gradients, which could be regarded as an indicator of the Meiyu front system, could be mainly attributed to the variations of atmospheric potential temperature gradients with a scaling factor of 1 and moisture gradients multiplied by a scaling factor of an order of about 2.5 × 10^3, which means that small variations of atmospheric moisture gradients could lead to large variations of equivalent potential temperature gradients, and thus large variations of the Meiyu front system. Quantitative diagnostics with a mesoscale simulation data in the vicinity of the Meiyu front system show that moisture gradients contribute to equivalent potential temperature gradients more than potential temperature gradients.

东海盆地西湖凹陷斜坡区平湖断裂带分段性及其成因机制

为了揭示平湖断裂带的形成及演化过程,厘定大型断裂分段特征及其地层充填响应,深化对复杂断裂发育机制的认识,本文基于最新的三维地震资料,开展了平湖断裂带几何学、运动学分析,并结合区域应力场分析探讨了断裂成因及发育模式。研究结果表明:平湖断裂带是由NE走向与近NS走向交替出现的三个分段和五条主干断裂构成的“X”型断裂带;NE向断层段形成时间较早,具有分段发育特征,近NS向断层段形成时间较晚,控制了南、中、北段的分段链接;平湖断裂带复杂断裂的形成受始新世时期断裂分段生长发育和区域应力场旋转两种因素的共同控制;平湖断裂带断陷期生长演化过程划分为早期NE向断裂分段发育阶段、中期NE—近NS向断裂硬链接阶段和晚期近NS—NNE/NE向断裂张扭改造阶段。平湖断裂带发育演化的时空差异直接影响着该地区局部沉积、沉降中心迁移及裂后期挤压反转背斜的发育。

东海北部和黄海南部鳀鱼卵和仔稚幼鱼数量、分布及其与环境条件的关系

1999年夏季鳀鱼卵和仔稚幼鱼主要分布于黄海南部,122°00′～123°45′E、34°00′～35°15′N与122°15′E以西海域分别为鳀鱼卵与鳀鱼仔稚幼鱼的密集分布中心,其表层水温和盐度分别为25.5～26.9℃和27.11～31.81与26.4～27.0℃和31.31～32.05。鳀鱼卵和仔稚幼鱼分布的最适表层水温分别为25.5～26.4℃和25.9～27.0℃;全长为20mm以上的鳀鱼稚鱼已初步形成广盐性分布的习性,鳀鱼卵和仔稚幼鱼的分布对盐度的要求并不非常严格,水温是影响鱼卵和仔稚幼鱼分布的主要原因之一。鳀鱼卵和仔稚幼鱼的分布与叶绿素a的分布也有密切的关系,鳀鱼卵和仔稚幼鱼的密集分布中心正是叶绿素a的高值区。随着季节的变化,黄海南部鳀鱼产卵场由青岛外海逐渐向深水区转移。黄海南部鳀鱼活卵所占的比例为45.76％,胚胎发育状况良好。

黄海、东海入海气旋爆发性发展过程的海气相互作用研究

基于 1 999年 6月中、韩、日三国联合调查的两个航次资料 ,对“黄东海入海气旋爆发性发展过程的海气相互作用研究”项目进行了物理海洋学与气象学相结合的研究 ,也结合了历史调查资料的研究 ,得到了以下主要结果 :( 1 )以 1 999年 6月资料与历史调查资料对黄海、东海海域黄海冷水团 ,长江冲淡水 ,黄海沿岸流 ,台湾暖流 ,黑潮及其两侧冷、暖涡等进行了水文分析 ,并采用了改进逆方法 ,P矢量方法 ,三维海流诊断、半诊断模式与预报模式 ,MOM2模式等 ,计算了 1 999年 6月与历史资料调查期间黄海、东海海域环流 ,结合锚碇测流与ADCP测流等的实际观测 ,揭示了调查海区各流系的时空变化 ,以及它们的相互作用 ,指出这些流系的相互作用对入海气旋发展过程有重要影响 .( 2 )计算了调查海区各流系的流速与流量分布等 .( 3)阐明了气旋发展过程中对海洋的反应 .( 4 )在 1 999年 6月海上调查时期观测发现 ,在气旋中心区等存在负的潜热通量和感热通量 .出现负的潜热通量和感热通量的海域分别位于黑潮以西、温度相对低的气旋涡区域 ,黄海沿岸水向东南方向流动 ,然后作气旋式弯曲处 ,济州岛西南冷的、气旋涡区海域等 .而观测发现 ,在黑潮区以及黑潮核心以东暖涡区出现的高的、正的感热与潜热通量 ,明显地与黑潮与暖涡区的?

春季中国东部海域气旋急流在气旋发展中的作用研究

对2008—2014年中国东部海域春季海上发展气旋进行了统计与诊断分析。结果表明:1)这类气旋属于较浅薄的低值系统,垂直伸展高度多在600 h Pa以下,水平尺度多在1 500 km以内。伴随的强天气为大风、大浪与强降水,落区主要位于气旋东南部。2)气旋环流各层的大风急流区构成了气旋的东南部位,称为气旋急流。从高层到低层,气旋急流轴在垂直方向上呈逆时针旋转,形成气旋上大下小的漏斗形状。3)气旋急流左侧的气旋式切变有利于气旋中心强度的维持,上层气旋急流左侧对应下层气旋急流前部流速辐合区,有利于气旋式动力抽吸及在气旋东南部形成强的垂直上升运动区。各层气旋急流配置导致气旋的非对称结构,以及气旋要素的非对称分布。气旋急流向气旋中输入螺旋度以及充足的水汽,并在东南部强烈抬升,增强了凝结潜热释放,从热力和动力两方面促进气旋发展及强天气落区。4)春季下垫面温度分布(锋区)有利于气旋急流的增强,并通过西北部非绝热冷却和东南部非绝热加热,增强气旋斜压性。高空环境西风急流位于气旋右侧,形成了整层偏差风辐合,有效增强低层气旋急流。同时高空动量下传位于气旋西侧,首先增强气旋西北部的弱流部分(即气旋螺旋结构的下沉支),进而增强整个气旋的螺旋环流,促使气旋急流也从下层开始增强。

中国发展战略与中国-东盟关系再认识

过去几年中国与东盟国家围绕南海问题产生的争议,在中国和东盟方面都引发了对中国—东盟关系的反思,一些人甚至提出了中国分化东盟的观点。从中国发展战略的内源性出发,本文认为东盟在中国发展战略中具有重要地位,中国重视东盟在推动地区经济发展及区域合作中发挥的积极作用。因此,中国分化东盟的观点是站不住脚的。然而必须承认,中国—东盟合作目前确实面临互信约束,部分东盟成员对中国的"一带一路"倡议仍在犹豫观望。从双边关系的发展来看,中国与东盟合作前景广阔,只是在这个过程中双方要共同努力消除互信赤字,这样才能真正在利益共享中逐步走向命运共同体。

不同发育阶段东、黄海凤鲚的食性差异

根据东海区（26°-35°00′N,120°00′-126°30′E）大面调查渔获物的凤鲚样本,对东、黄海凤鲚不同发育阶段的食物组成、摄食强度、食物生态位宽度和食物团单个饵料的重量差异进行了研究,并对不同体长组的凤鲚进行了聚类分析。研究结果表明：（1）凤鲚不同阶段的食物组成随着发育的变化有所不同,根据%IRI分析,桡足类为各个发育阶段的最重要的食物,糠虾类、磷虾类为次重要的类群,随着体长的增加小型鱼类在食物组成的%IRI比重越来越高。（2）凤鲚有两个摄食强度的高峰：幼体组70～100 mm和成体组191～250 mm,平均胃饱满系数均超过10‰。空胃率和体长呈现出负相关关系,随着体长的增加,空胃率不断下降。（3）食物团中单个饵料的平均重量随着凤鲚体长的增加而增加,两者呈现正相关关系。体长70～160 mm阶段,单个饵料的平均重量都小于10 mg,体长161～250 mm阶段,单个饵料的平均重量均大于30 mg。（4）聚类分析表明可将的凤鲚6个体长组可以分为3组：70～100 mm、101～130 mm、131～250 mm。体长70～100 mm的凤鲚主要以桡足类和幼体类为食,体长101～130 mm的凤鲚主要摄食桡足类、糠虾类和磷虾类,体长131～250 mm的凤鲚主要摄食桡足类、糠虾类和鱼类。（5）凤鲚不同发育阶段食物生态位宽度也存在差异,体长101～130 mm饵料多样性指数最高为2.37,体长70～100 mm饵料多样性指数最低为0.96,体长131～250 mm之间各体长组饵料多样性指数相差不大。

中日东海油气资源共同开发中的争端解决

中日东海油气资源之争在双方2008年达成《关于中日东海问题的原则共识》之后可谓进入了一个新的阶段,中方认为可在明确东海大陆架包含的自然资源(尤其是油气资源)主权属于中国的前提下,双方初步划定共同开发区的范围。此后双方需要考虑的就是在划定的"区块"内,建立何种经营模式,构建怎样的争端解决机制。经过对同类案例的比较和研究,可以得出联合经营模式为最佳,与此同时应当分两种情形(中方一侧"区块"和争议范围内"区块"),考虑三种主体(国家、开发机构和承包商)之间的争端解决方式,如此便可较为全面地涵盖中日共同开发区内的争端。

论东海问题本质与解决思路

中日两国举行的东海问题原则共识政府间换文谈判,是落实两国政府首脑达成共识的具体措施。即使两国经过谈判取得一定的成绩,但东海问题的全面解决仍很遥远。因为两国针对东海问题的立场与主张严重对立,无法消弭。同时,换文谈判的依据《原则共识》只是一个局部性和过渡性的安排,特别是其存在根本性的缺陷,主要为没有界定东海问题的内涵、没有对钓鱼岛列屿问题作出交代,需要补正。而东海问题的本质是钓鱼岛列屿争议问题。为此,本文指出了东海问题的基本内涵,分析了针对东海问题的歧见,并探讨了解决东海问题包括钓鱼岛列屿问题的路径,以期对认识和理解东海问题的本质有所帮助,并望有助于东海问题的最终解决。

衡平原则及其在东海划界中的适用

衡平原则是大陆架划界中已经确立的习惯法规则,它的基本理念可以追溯到1909年常设仲裁法院的瑞典和挪威格里期巴丹那岛案。在该案中,常设仲裁法院首次"衡平考虑"了现实情况。在随后的国际实践中,各国都将衡平原则作为大陆架划界的前提和基础,经过国际法院和国际司法实践的推动,衡平原则逐步成为大陆架划界中受到普遍承认的习惯法规则。文章从衡平原则的发展过程入手,分析了衡平原则的法律地位和发展趋势,认为在中日东海大陆架划界中,衡平原则应当是首先适用的国际法规则。

油藏隔离工艺技术在东海压力混合低渗储层勘探开发一体化作业中的应用

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