日照市近海海域灾害地质类型及特征分析

日照近岸海域灾害地质类型主要为埋藏下切谷、海底侵蚀、冲刷沟槽和冲刷陡坎及海底抛泥区等。通过对日照海岸带近岸海域的浅地层剖面和水深测量资料,开展主要地震地层界面的追踪和对比,结合沉积物粒度和地球化学特征,对近海海域潜在灾害地质因素进行分析对比,探讨了日照近海海区的灾害地质类型、特征和分布规律,为半岛蓝色经济区的海洋开发提供基础地质资料。     

威海市近海海域浅地层结构及灾害地质特征

通过对2 131km高分辨率浅地层剖面资料分析和研究,揭示了威海市近海海域浅地层结构特征,分析了海洋灾害地质因素类型及分布特征,并绘制了主要灾害地质因素分布图。威海市近海海域65m以浅地层共分为5层,第一层为全新世泥质楔形体,地层厚度8~15m;第二层为末次盛冰期以来的海侵层,厚度一般小于3m;第三层为MIS2期的陆相沉积层,地层厚度3~8m;第四层为MIS3期的海相沉积层,厚度3~6m;第五层未完全揭示。近海海域灾害地质因素主要包括埋藏下切谷、浅部断层、浅层气、海底沙波沙脊、浅埋起伏基岩等5种类型;埋藏下切谷主要分布在南部海域U3地层单元中;浅部断层主要分布在南部海域水深大于20m的海底堆积平原;浅层气主要分布在北部海域,东部和南部海域面积较小;海底沙波沙脊主要分布在荣成成山头外海海域;浅埋起伏基岩主要分布在基岩海岸和岛屿较近的海域。     

地质模式约束的SVR属性融合在浅水三角洲储层描述中的应用: 以西湖凹陷X气田为例

X气田位于东海盆地西湖凹陷中央反转构造带,主要目的层H4层为浅水三角洲沉积环境,气田地震资料主频较低（25 Hz）,而H4层埋深较大（3 300~3 400 m）,储层低孔低渗,常规地震反演预测砂体厚度吻合度较低。针对X气田三维地震资料全覆盖及钻井较少的特点,通过地质模式指导下的正反演结合设置虚拟井来弥补SVR（Support Vector Regression）算法中样本点的不足,通过提取地震属性并优选表征砂体厚度的敏感属性,利用SVR算法进行多属性融合,完成了H4层砂体的定量预测。基于储层预测成果,提出H4层为浅水三角洲曲流型分流河道沉积,并进一步完成了砂体沉积模式解剖,成功指导了开发调整井部署,实钻砂体厚度与预测砂体厚度吻合度高达84%以上。探索得到了海上少井条件下地质模式约束的SVR算法储层定量预测方案,对X气田中深层分流河道储层完成了精准预测,亦对同类型油气田的储层描述具有一定指导意义。      

东营近海海域地质环境质量评价

该文在东营市海洋地质调查获得大量数据的基础上,开展近海海域地质环境质量综合评价,反映近海海域地质环境质量现状和变化趋势,为海洋经济的可持续发展和海洋生态环境保护提供依据。选取海岸侵蚀与淤积、活动断裂与地震、灾害地貌与滑坡、浅层气、底辟、埋藏古河道(古湖泊)、表层沉积物质量、海水质量、软土、砂土液化10项指标,采用层次分析法和综合指数法,对东营市近海海域地质环境质量进行了评价。结果表明:研究区大部分区域地质环境质量为优等和良好级别,面积8875km~2,占总面积的86.58%;中等区主要分布在研究区的北部、东南部和东营港近岸区,面积1200km~2,占总面积的11.71%;较差区主要分布在研究区的北部及黄河口外围海域,面积175km~2,占总面积的1.71%。     

A preliminary study of tidal current ridges

Tidal current ridges, widely distributed geomorphological phenomena over the continental shelf of the world, are studied. They are formed by tidal current and the trend of their sand bodies runs parallel to the direction of tidal current. There are two types of the plane shapes: the parallel and the fingered. Conditions of forming tidal current ridges are the velocities of tidal current ranging from 1 to 3.5 knots and the supply of abundant sediments. Tidal current ridges often develop in following morphological locations: the bays, estuaries, the mouths of channels, as well as the offshore area with strong tidal current. Tidal current ridges occur generally at a water depth of less than 35 metres. The sediments of tidal current ridges are mainly composed of sand. The grain size of the sediments is uniform and well sorted. The characteristics of grain size of the sand imply that their formation mechanism is similar to that of river sand, that is, both of them are the result of flow movements in a trongth channel controlled by boundary. There is however difference between them that the river sand is formed by one-way flow movement while the tidal current sand by two-way movement. There are two saltation populations in the log-probability curves of tidal current sand, the sorting of first saltation population is better than the second one, and having positive skewness, which differs from beach sand. In the C-M grain size pattern tidal current sand is most found in graded suspension segment. The continental shelves of the Yellow Sea, the East China Sea and the South China Sea have favourable conditions for developing tidal current ridges in massive scale and special shape, such as the tidal current ridges in the offshore of Jiangsu, the Gulf of Korea, the shoal of Liaodong, the east and west mouths of the channel of Qiongzhou, Jiaozhou Bay, the shoal of Taiwan, Lingdingyang, the north branch of Changjiang estuary. The studies of them are of vital significance in shipping, fishing, submarine engineering, military installations, oil and gas explorations, as well as in scientific research. This paper was published in Chinese inOceanologia et Limnologia Sinica 14 (3): 286–296.     

水域地震映像在火成岩发育区的应用与探讨——以厦门某海底隧道勘察为靶区

以厦门某海底隧道勘察为靶区，采用电磁气泡震源系统激发地震波，在火成岩发育区进行水域地震映像实验，较好地查明了海底水深界面、淤泥（砂层）和基岩面的分界线。实验结果表明，水域地震映像法对海域火成岩发育区是一种有效的物探方法，可以为海域地质勘察提供可靠的地质参考依据；利用水域地震映像勘探既可以较好地弥补钻探缺陷，又能极大地节约经济成本。     

Seismic data processing approaches for the study of gas hydrates in the east China sea

A comprehensive study of the data profiles, including the 2D seismic data, single channel seismic data, shallow sections, etc., reveals that gas hydrates occur in the East China Sea. A series of special techniques are used in the processing of seismic data, which include enhancing the accuracy of velocity analysis and resolution, estimating the wavelet, suppressing the multiple, preserving the relative amplitude, using the DMO and AVO techniques and some special techniques in dealing with the wave impedance. The existence of gas hydrates is reflected in the subbottom profiles in the appearance of BSRs, amplitude anomalies, velocity anomalies and AVO anomalies, etc. Hence the gas hydrates can be identified and predicted. It is pointed out that the East China Sea is a favorable area of the gas hydrates resource, and the Okinawa Trough is a target area of gas hydrates reservoir.     

威海市海岸带地质环境承载力综合评价研究

该文在威海市海岸带综合地质调查项目的基础上,根据陆域和海域不同的地质环境条件,分别进行了地质环境承载力综合评价。陆域选取了3个一级评价因子和13个二级评价因子建立地质环境承载力评价指标体系,利用层次分析法取得各评价因子权重,再利用模糊数学综合指数法进行了综合评价。海域选取了海底沉积物重金属污染、海底沙坡沙脊、浅层气、浅埋基岩和埋藏下切谷等5个评价因子,采用叠加法进行了综合评价。最终,将研究区地质环境承载力划分为强区、较强区、一般区、较弱区等4类。研究区陆域地质环境承载力相对较强,占总面积的67.67%;其次为一般区,占总面积的31.67%;较弱区零星分布,仅占总面积的0.66%。近海地质环境承载力总体较强,一般区主要分布在威海湾西部,较弱区分布在威海湾以北的广阔海域。     

Potential submarine geologic hazards at the entrance of the Pearl River Estuary in the northern South China Sea

The potential submarine geologic hazards were distinguished and categorized at the entrance of the Pearl River Estuary in the northern South China Sea, based upon the analysis of side scan sonar and sub-bottom profiler surveying data of about 2500 km long, in an area about 2000 km~2 around the Wanshan Archipelago. The data obtained in the survey has the highest spatial resolution by far, which could reveal more detailed distributions and characteristics of the geologic hazards than before. In the study region, three paleo-channels that were buried about 10–30 m below the seabed were found; more than 10 shallow gas areas were discovered. The sand waves found in the region were generally small and located near the islands, and twenty pockmarks found on the seabed were mostly concentrated to north of Zhuzhou island. There are also many man-made obstacles in the region, such as wreckages, pipeline, etc. In this paper we provide a detailed distribution map of the submarine geologic hazards in this region for the first time, and discuss their formation and harmfulness, which will provide a scientific basis for marine engineering construction, marine geologic disaster prevention and mitigation.     

An application of marine geomagnetic survey to shallow sea engineering geology

A marine geomagnetic survey was conducted over Red Bay, a broad shallow sea area in the southern part of the Shandong Peninsula, to obtain geological information to meet the needs of an underwater engineering project. Analyses of magnetic data revealed the fault structure of the bedrock and differences in lithology. At the proposed offshore dam site, the magnetic survey results indicated the position of faults which have since been confirmed by other geophysical surveys.     

Offshore Fault Geometrics in the Pearl River Estuary,Southeastern China: Evidence from Seismic Reflection Data

The Pearl River Estuary (PRE) is located at the onshore-offshore transition zone between South China and South China Sea Basin, and it is of great significant value in discussing tectonic relationships between South China block and South China Sea block and seismic activities along the offshore active faults in PRE. However, the researches on geometric characteristics of offshore faults in this area are extremely lacking. To investigate the offshore fault distribution and their geometric features in the PRE in greater detail, we acquired thirteen seismic reflection profiles in 2015. Combining the analysis of the seismic reflection and free-air gravity anomaly data, this paper revealed the location, continuity, and geometry of the littoral fault zone and other offshore faults in PRE. The littoral fault zone is composed of the major Dangan Islands fault and several parallel, high-angle, normal faults, which mainly trend northeast to northeast-to-east and dip to the southeast with large displacements. The fault zone is divided into three different segments by the northwest-trending faults. Moreover, the basement depth around Dangan Islands is very shallow, while it suddenly increases along the islands westward and southward. These has resulted in the islands and neighboring areas becoming the places where the stress accumulates easily. The seismogenic pattern of this area is closely related to the comprehensive effect of intersecting faults together with the low velocity layer.     

Application of seismic interferometric migration for shallow seismic high precision data processing: A case study in the Shenhu area

The stability of submarine geological structures has a crucial influence on the construction of offshore engineering projects and the exploitation of seabed resources. Marine geologists should possess a detailed understanding of common submarine geological hazards. Current marine seismic exploration methods are based on the most effective detection technologies. Therefore, current research focuses on improving the resolution and precision of shallow stratum structure detection methods. In this article, the feasibility of shallow seismic structure imaging is assessed by building a complex model, and differences between the seismic interferometry imaging method and the traditional imaging method are discussed. The imaging effect of the model is better for shallow layers than for deep layers because coherent noise produced by this method can result in an unsatisfactory imaging effect for deep layers. The seismic interference method has certain advantages for geological structural imaging of shallow submarine strata, which indicates continuous horizontal events, a high resolution, a clear fault, and an obvious structure boundary. The effects of the actual data applied to the Shenhu area can fully illustrate the advantages of the method. Thus, this method has the potential to provide new insights for shallow submarine strata imaging in the area.     

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.     

Deep-sea geohazards in the South China Sea

Various geological processes and features that might inflict hazards identified in the South China Sea by using new technologies and methods.These features include submarine landslides,pockmark fields,shallow free gas,gas hydrates,mud diapirs and earthquake tsunami,which are widely distributed in the continental slope and reefal islands of the South China Sea.Although the study and assessment of geohazards in the South China Sea came into operation only recently,advances in various aspects are evolving at full speed to comply with National Marine Strategy and‘the Belt and Road’Policy.The characteristics of geohazards in deep-water seafloor of the South China Sea are summarized based on new scientific advances.This progress is aimed to aid ongoing deep-water drilling activities and decrease geological risks in ocean development.     

Numerical Simulation for Shallow Strata Stability of Coral Reef in the Southwest of Yongshu Reef (South China Sea)

In recent years, infrastructure construction on coral reefs has been increasingly developed. Therefore, the shallow strata stability of coral reefs in the South China Sea should be evaluated. This study aims to investigate the profiles for the shallow strata of coral reefs in the southwest of the Yongshu Reef, particularly in the hydrodynamic marine environment, and to establish a geological model for numerical simulation using Geo-Studio. The shallow strata of the coral reefs include mass gravel, sand gravel, mid-coarse sand, silty sand, fine sand, and reef limestone. The shallow reef slope near the lagoon is similar to a ‘layer cake', in which the side close to the sea is analogous to a ‘block cake'. The simulation results showed that coral reef stability depends on wave loads and earthquake strength and on the physical properties of coral reefs. The factor of safety for the outer reef is greater than 10.0 under static, wave, and seismic conditions; this indicated that the outer reefs were less affected by waves and earthquakes. However, the factor of safety next to the lagoon varied from 0.1 to 5.3. The variation was primarily caused by the thick strata of coral reefs close to the sea(reef limestone, typically with the thickness 10 m and equivalent to a block). The soil and rock layers in the coral reef strata with thicknesses 10 m showed weak engineering geological characteristics. Our findings can provide useful information to future construction projects on coral reefs.     

Spatial distribution and controlling factors of sedimentary bodies in Jiaozhou Bay and Adjacent Sea Areas, Qingdao

The distributions of thickness of unconsolidated Quaternary sedimentary layers in Jiaozhou Bay and Qingdao offshore area were studied by using 1079-km high-resolution shallow seismic profiles and drilling core data, and the factors controlling the Quaternary evolution were discussed. The results show that such thickness distributions resulted from the coactions of geologic structures and marine hydrodynamic conditions since the Holocene. The geologic structures controlled the slope deposit, proluvial and fluvial fillings since the late Pleistocene. Holocene marine hydrodynamics eroded away sediments at the bay mouth, and tides carried these eroded materials to the sides of the bay mouth and released them there, forming channel-ridge-alternating geomorphic features. During transgressive processes, the sea level rose rapidly, and insufficient sediment supply and tidal actions yielded the relict sediments in the east of Qingdao offshore area.     

Foraminiferal Changes and Response to the Channel Diversion and Discharge Fluctuation of the Yellow River in the North Yellow Sea During the Past Century

Diversion of the Yellow River is a unique geological event in offshore China, causing changes of the sedimentary environment in eastern China Seas. The last diversion took place in AD 1855, with the estuary diverted from the Yellow Sea into the Bohai Sea. The identification of the river diversion events in the shelf sediments would not only provide the definite ages for the sediments, but also give a clue for better understanding of the sedimentation in that area. In this study, 210 Pb, grain size, geochemical element, and foraminiferal data in core H205 from the north Yellow Sea were systematically investigated. A high-resolution sedimentary record was established, which was coupled with the Yellow River diversion and runoff changes. The results show that the foraminiferal composition and foraminiferal abundance of the sediments from the north Yellow Sea had good response to the Yellow River diversion in 1855. Before the change, shallow water assemblages dominated the foraminifera, and the abundance of each foraminiferal species was very low. After the diversion event, the abundance of most foraminifera increased sharply, with a maximum increase of 16 times, and the assemblage was still dominated by shallow water species. Furthermore, the changes in foraminiferal abundance in the core sediments corresponded well with the discharge fluctuation of the Yellow River since 1855. When the Yellow River began entering the Bohai Sea, the Yellow River water, which is rich in nutrients, along with the coastal currents affected the north Yellow Sea, increased the primary productivity in the north Yellow Sea, which is the main reason for the abrupt increase and fluctuation of foraminiferal abundance in this area. At the meantime, the East Asian winter monsoon could also promote the development of nearshore foraminiferal species by enhancing the coastal currents.     

东海油气地质特征与开发方案研究

本义以东海陆架盆地地质调查和勘探开发的实际资料为依据，阐明了东海海底地形、地貌及地质特征；强调了近年来在石油地质学理论研究中的重要突破及石油勘探中的重要进展。文章分析了东海地层分布及其含油气规律；重点解剖了西湖凹陷及台北坳陷的油气资源富集特征；探讨了东海油气田早期开发利用方案；并指出了其开发的巨大经济价值和良好的前景。     

Accumulation and exploration of gas hydrate in deep-sea sediments of northern South China Sea

The large deep-sea area from the southwestern Qiongdongnan Basin to the eastern Dongsha Islands,within the continental margin of northern South China Sea,is a frontier of natural gas hydrate exploration in China.Multiform of deep-sea sedimentations have been occurred since late Miocene,and sediment waves as a potential quality reservoir of natural gas hydrate is an most important style of them.Based on abundant available data of seismic,gravity sampling and drilling core,we analyzed the characteristics of seismic reflection and sedimentation of sediment waves and the occurrence of natural gas hydrate hosted in it,and discussed the control factors on natural gas hydrate accumulation.The former findings revealed the deep sea of the northern South China Sea have superior geological conditions on natural gas hydrate accumulation.Therefore,it will be of great significance in deep-sea natural gas hydrate exploration with the study on the relationship between deep-sea sedimentation and natural gas hydrate accumulation.     

地震沉积学在河流-浅水三角洲沉积相研究中的应用: 以渤海海域蓬莱A构造区馆陶组为例

庙西南凸起蓬莱A构造区馆陶组有良好油气发现,但储层厚度多小于5 m,难以被精确识别刻画。以薄层砂体为研究对象,综合地震、测井、钻井岩心、古生物等基础资料,明确研究区馆陶组沉积时期受北东向物源供给沉积,发育河流-浅水三角洲相。基于90°相位化处理确定砂体地震响应特征;分频解释处理判断相对等时地震同相轴,构建馆陶组高频层序地层格架（三级层序SQ1-3）,优选60Hz地震数据体进行地层切片划分;地层切片高精度沉积学解释揭示研究区馆陶组SQ1层序至SQ3层序依次发育河流-席状化浅水三角洲-朵叶状浅水三角洲-水下河道型浅水三角洲。其中SQ1层序中河道砂体以及SQ2-3层序中浅水三角洲前缘砂体皆为有利储层。此次研究丰富发展了渤海海域河流-浅水三角洲相中地震沉积学在砂体预测中的研究成果。