八. 海洋地球物理

(负责人：王光宇 王家林 宋海斌)

Marine Geophysies

(Conveners: WANG Guangyu WANG Jialin SONG Haibin)

1. Methods and Techniques of Studying Geological Fracture Surface with Gravity and Magnetic Data in Sea Area

Gao dezhang Tang jian et.

(Shanghai Offshore Petroleum Planning & Designing Institute shanghai 200120 )

Abstract: This paper introduces technical methods of studying deep structure of the Earth’s crust in sea area by a typical profile with gravity and magnetic results , obtaining shape and imbedded depth of sedimentary basement 、Courie isothermal surface 、Moho surface in 3-d space. Three key techniques are introduced in this paper, for example the reduced to the pole of magnetic anomalies at the low latitude , the analysis of gravity and magnetic field and the 3-d forward simulation . At the moment a few pieces of advice on gravity and magnetic interpretation are brought forward.

2. The process and extract of original multi-beam data

Fang Yinxia Gao Jinyao

The Second Institute of Oceanography & Key Lab of Submarine Geoscience, State Oceanic Administration, Hangzhou 310012

Abstract: This paper introduced the process and extraction of original multi-beam data system briefly. Based on the analysis of the original multi-beam data structure, the system established its own inner data structure, and developed a dynamic link library for transforming the different formats multi-beam data. Recur to this DLL, the user can read/write many different formats multi-beam data, and extract the contents of the data which the user needed.

3. Resource Evaluation Of Marine Gas Hydrates

Li Mingbi Jin Xianglong Fang Yinxia

(Second Institute Of Oceanography, SOA; Key Lab Of Submarine Geoscience, Hangzhou, 310012)

Gas hydrates have become an exciting national and international research issue, most researches are related to its energy potential, and its influences on seafloor stability and globe changes. But the resource evaluation of gas hydrates is believed to be the foundation for the related researches. In this paper, authors propose the conceptual model for the resource evaluation of marine gas hydrates using numerical model, with the assumptions that the formation, stability and dissolves of marine gas hydrates are mainly controlled by temperature and pressure conditions. The conceptual model includes geological background, geothermal and pressure fields of water layer and seafloor sediments, and the methods to determine the thickness and distribution of gas hydrates stability zone (HSZ).

4. Character and propagation mechanism of radial wave on hydraulic pressure profile
 Yao Chen   Xun Wang          and     Xiangguo Chen
 Institute of Geology CSB, China, 100029  
 Institute of Geophysics CSB, China, 100081
    There often records waves appearing as radial propagation on hydraulic records in sea floor exploration. Such wave has linear time-distance ahead of reflection from seabed and shows repeated emerging like other multiples. Hydraulic pressure profiles have been calculated by reflectivity technique. For sea floor model including hard seabed and high velocity thinner layer, the radial waves with strong amplitude appear different from head wave as usually explanation. If assuming zero shear-wave velocity in high velocity layer, the radial waves disappeared indicating this wave have shear-wave ray path within such layer. Also radial wave could not be interpreted by ray method because curved wave fronts are necessary. As increasing the thickness of high velocity layer, the amplitudes of radial wave will decrease and no signal could be observed eventually. The mechanism of radial wave could be explained: P-wave in water generates shear-wave on liquid-solid boundary, the down going shear-wave penetrates high velocity layer with critical angle and radial propagates as inhomogeneous wave within the layer then up going as shear-wave, finally converted to P-wave in water. Based on our explanation in this paper and further quantitative study, it is hopeful to get information about high velocity thinner layer of sea floor from radial wave recorded.
    NSFC NO. 49874012 supports this work.

5. Investigating medium condition on radial wave by synthetic sea floor reflection
   Xun Wang  and  Yao Chen
   Institute of Geology CSB, China, 100029
   Abstract

    Based on the declaration of property and mechanism of radial wave on hydraulic pressure records (Yao Chen et al., this issue), the corresponding medium condition for radial wave emerging has been discussed by synthetic seismograms in this paper. The sea floor models with varied parameters but including high velocity layer (HVL) are used for comparison of radial wave characteristics. As increasing thickness of HVL, the amplitudes of radial wave are decreased. Such waves can not be observed when the thickness of HVL is beyond 200m but are very strong in case of thinner layer. The synthetics for wider range of shear-wave velocity of seabed show that the energy of radial wave is also affected by hard or soft seabed condition beneath water layer. As depth of HVL decreased, the radial wave will emerge ahead of main reflection from sea floor at shorter offset and vice versa. Because there is the strong velocity jump both for seabed and HVL where dominant reflection and/or multiples will occur, the quantitative interpretation of high velocity layer is required in combination with explanation the whole feature of records.
 NSFC NO. 49874012 supports this work.

6. 多波束声速改正的主要影响因素及其精度控制方法

李家彪、郑玉龙、陶春辉

国家海洋局海底科学开放实验室，杭州，310012

Main factors affecting multibeam SVP correction

and their precision control method

Li Jiabiao, Zheng Yulong and Tao Chunhui

(Key lab of geosciences SOA, Hangzhou, 310012)

With discussion of the formula transforming travel-times to water-depths and four basic hypotheses, three main factors affecting multibeam SVP (sound velocity profiles) corrective precision are present by modeling analyses: SV (sound velocity) differences in surface layer, SV jumps and their depth differences, and transducer heaves in shallow SV jumps. The features of universality and regional distribution of these three situation and possible methods to control SVP corrective precision are pointed out in multibeam measurement.

7. 南海东部海盆多波束数据处理及其构造意义

李家彪、金翔龙、高金耀

国家海洋局海底科学开放实验室，杭州，310012

Multibeam data processing of east subbasin of South China Sea

and its tectonic significance

Li Jiabiao, Jin Xiangilong Gao Jinyao

(Key lab of geosciences SOA, Hangzhou, 310012)

The South China Sea is a great one of the western pacific marginal-sea basins, and consists of three oceanic-crust subbasins (East subbasin, SW subbasin and NW subbasin) and several thinning continental-crust blocks. Among all geological problems about the South China Sea, the geodynamic process has long been the focus of many geoscientists. Researchers have put forward a series of evolution models and the direction of late stage spreading in East subbasin still is the matters of debate.

With 25 thousand km multibeam data processing of East subbasin of South China Sea, it’s clear that NE-trending linear morphological features such as scarps, horst and graben, govern the center part (17°–14°N) of East subbasin, and could be divided into three symmetrical structure zones. The center zone trends NE45°-50°, second zone NE55°-60°and third zone about NE50°. Combined with several seismic profiles, these NE-trending linear morphological structures are well consistent with basement structures. So the spreading direction of center part of East subbasin is NW-SE, and can be subdivided into three tectonic stages.

8.The characteristics of seismic reflections in the central basin

of the South China Sea and their tectonic significance

Liu Jianhua

(Second Institute of Oceanography, SOA, Hangzhou 310012 )

Abstract－The paper is based on the interpretation of more than 4000 km 48-channel reflection seismic data as well as the analysis of other geophysical and geotectonic information. There are four seismic reflection sequences named I~IV in the central basin of the South China Sea (SCS). Sequence IV with the age of Oligocene is mainly developed in the northern section of the east subbasin (ESB) and the northwest and southeast magins of the southwest subbasin (SWSB). It is indicated that the ESB has been evolving since Oligocene and the origin of the SWSB may be earlier than Oligocene. The reflections from Moho have been found on the profiles acrossing the central basin of the SCS, whose depth varies between 10 and 12 km.

9. 多金属结核分布与地形坡度的关系

王英 吕文正 何拥华

国家海洋局海底科学重点实验室

国家海洋局第二海洋研究所，310012

9.The Relationships Between the distribution of Polymetallic nodules and terrain slope

Wang Ying Lu Wenzheng He Yonghua

(Key Lab of Submarine Geosciences, SOA, 310012)

Many studies indicate that there are very closely relationships between the distribution of Polymetallic nodules and submarine terrain slope. The study of submarine terrain is mainly based on multi-beam measuring. Because multi-beam system works on the 5000 meters height above sea bottom, the calculated slope from multi-beam data is smaller than it’s real slope. At the same time, the data of the distribution of Polymetallic nodules is from geologic sampling and submarine photography, we couldn’t get the continuous distribution of Polymetellic nodules because of the sparse site. The deeptow optical system can measure the continuous varieties of the terrain and the distribution of Polymetallic nodules. It works closely to bottom of the sea, so the calculated slope is more precise. We can discuss the relationships between the distribution of Polymetallic nodules and terrain slope more quantificational.

We processed the deeptow optical measuring data of 10 measuring lines from two areas, which is East Area and West Area in the East Pacific Pioneer Area of CHINA. The statistic indicates that east slopes are in proportion to west slopes, the terrain undulates acutely in East Area, and the terrain undulates gently in West Area. In East Area, the slopes between 1～2°are in the majority, 0～1°, 2～3°, 0°gradationally decrease, most slopes are less than 15°. In West Area, most slopes are less than 3°, 0～1°and 1～2°are in the majority, 0°and 2～3°are in the second. In East Area, the coverage of Polymetallic nodules between 0～35% is in the majority, all the coverage is less than 60%, accordingly the terrain slopes are less than 10°. In West Area, the coverage of Polymetallic nodules between 0～60% is in the majority, all the coverage is less than 70%, accordingly the terrain slopes are less than 5°.

We found in all the area we studied that Polymetallic nodules mainly distribute in the area whose slopes are less than 3°; In East Area, the coverage of Polymetallic nodules is mostly zero, accordingly slopes are larger. The coverage of Polymetallic nodules between 5～25% are in the second. In West Area, the coverage of Polymetallic nodules is mostly 50～60% , accordingly slopes are smaller. The coverage of Polymetallic nodules between 10～50% are in the second. In East Area, Polymetallic nodules mostly distribute in west slope. In West Area, Polymetallic nodules distribute symmetrically in west and east slopes.

10. The Methods to Get Thermal Properties of Gas Hydrates
Jin Chunshuang    Wang Jiyang

(Institute of Geology and Geophysics, Chinese Academy of Sciences, 100029)
An understanding of the in situ thermal properties (e.g., thermal conductivity and thermal diffusivity ) of gas hydrates in marine sediments is important for analyzing the effects of gas hydrate on thermal gradients, for accurately estimating temperatures at the depth of the bottom simulating reflector, and for calibrating empirical relationships with other physical properties, such as seismic wavespeed. The methods to get thermal properties of gas hydrates mainly are: in situ sample test, synthesized sample test in laboratory, and. The first method depends on in situ gas hydrate (bearing) sample cored on ODP. The second method depends on synthesized sample in laboratory. The third method depends on the “hydrate-coated-grain” model utilized the relationship between electrical and thermal conductivities.


11. 多波束勘测数据高精度综合处理技术研究

吴自银 李家彪

（国家海洋局第二海洋研究所&海底科学实验室，杭州，310012）

The Study on High-precision Integrated Processing of Multi-beam Survey Datum

Wu Zi-yin Li Jia-biao

(Key Lab of Submarine Geosciences ,SOA, Hangzhou 310012)

The precision of the multi-beam survey data affects its reliability and usage, the multi-beam system parameters, the acoustic structure and the noises are the key factors, the data precision is combined controlled by these factors, so it is difficult to improve the precision of the survey data through the simple method of corrective or editing. Based upon the experience of manipulating different multi-beam systems and the latest outcomes of software development about multi-beam post-processing in the marine field of 863 project, this paper analyzes the factors of effecting the precision of multi-beam survey data, then proposes the methods of correcting the system parameters and the acoustic structure, and proposes to the methods of removing noises by the trend-surface fitting and the projective. And based on the projective method, the paper put forward the methods of editing multi-beam survey data subtly by “depth layering”, “comparing adjacent beams and lines”, and “referring to the tendency of the topography changes”.

12. 基于图层的海底地形电子成图子系统MBMap

吴自银 高金耀

(国家海洋局第二海洋研究所&海底科学重点实验室，杭州，310012)

The Submarine Mapping Sub-system MBMap Based on Graphics Layers

Wu zi-yin Gao jin-yao

(Key Lab of Submarine Geosciences ,SOA, Hangzhou 310012)

This paper briefly discusses the submarine mapping system MBMap based on the graphics layers of GIS. This system processes the vector data and grid data. Its excellent feature is automatic mapping based on the submarine DTM, it not only creates the contour map with variable contour level, but also builds the contour tree based on the map boundaries, so displays color filled vector map quickly and accurately. In addition, it draws the 3-dimension map based on the OpenGL technology. It provides the normally editing and mapping functions of GIS, and provides the vector function through man-machine conversation, it can be directly applied on the GPS navigation as well. Because of its successful design and achievement, it will possibly provide the prototype for the study of “Digital Ocean”.

13.深海声波资料的动力学解释

王公念 梁东红 梁 劲

（广州海洋地质调查局第二海洋地质调查大队，广州，510760）

DYNAMIC INTERPRETATION OF SONIC WAVE IN DEEP SEA

Wang Gongnian Liang Donghong et.al

(Second Marine Geologial Brigade, Guangzhou Geologial Survey,Guangzhou 510760)

The sonic energys of differential frequency gained from computer are different in nodule area of different-sized nodules, which are sonic dispersion. The correlation of sonic energys with nodule size indicates that the nodule size in different nodule regions can be discriminated according to the distributional patterns of sonic energys.

14. 海 洋 大 地 电 磁 正 反 演 初 探

中国地质大学（武汉），武汉，430074

Marine Magnetotelluric Forward And Inversion

Yang Meixia Zhang Shengye

Abstract It is said that twenty-first century is sea’s century. Exploring ocean is very important to every country. Geophysical methods are necessary ways to exploit sea bottom. Our country has paid much attention to the study of marine electromagnetism and introduced it into the ‘863 ’ project. This article discusses the marine magnetotelluric forward and inversion problems and programs a procedure for two-dimension forward. This procedure used finite element method to get electromagnetic field values at every node on the sea floor, at last calculated the impedance and apparent resistance on sea bottom. The results could successfully reflect the electric structure on sea bottom. To testify the practicability and validity of this procedure, we derived the equation for calculating one-dimension sea models, gave the exact resolution of them on bottom according Cagniard’s theory, and compared them with the results obtained by finite element method. The results suggest that the method discussed here is useful to exploring ocean. At last we do some inversion works: Bostick Inversion and RRI Inversion for one and two-dimension models.

Keywords: Marine Magnetotelluric Forward Inversion Finite Element Method

15. 东海盆地海礁隆起重磁力特征综合研究

陈冰 王家林 吴健生 钟慧智

（同济大学 教育部海洋地质重点实验室,上海 200092）

Integrated Study of Gravity and Magnetics

in Haijiao Uplift,East-China Sea

Chen Bing Wang Jialin Wu Jiansheng Zhong Huizhi

(Key Laboratory of Marine Geology, Tongji University, Shanghai 200092)

Abstract: In this paper, after the old and new lines are integrated, the data of gravity and magnetism at Haijiao Uplift in East China Sea is processed。Then the sedimentary thickness and it's structure feature in Neogene, depth of metamorphaic basement, the faults and igneous rock are studied comprehensively through the integrated interpretation with the material of gravity, magnetism, seismic and drilling in this area. Finally, some valuable recognition is acquired as the direction for oil evaluation and further study.

16. 关于开展海洋工程和地质灾害调查中的

海洋电法研究的几点设想

王家林 吴健生 王一新

（同济大学 教育部海洋地质重点实验室,上海 200092）

Some Thought about the Study of Marine EM Methods

In Investigation of Marine Engineering and Geological Disaster

Wang Jialin Wu Jiansheng Wang Yixin

(Key Laboratory of Marine Geology, Tongji University, Shanghai 200092)

Abstract: With the consideration of the changing situation in Marine EM Methods, in the paper, the possibility and the key technology are discussed in the application of Transient EM and High Density Resistivity Method.

17. 江苏某沿海区综合物探研究技术

吴健生¹ 王家林¹ 陈高² 李代芳²

（1、同济大学 教育部海洋地质重点实验室,上海 200092）

（2、江苏石油勘探局 江都 江苏225261）

Integrated Geophysical Study

In Coastal area, Jiangsu Province

Wu Jiansheng¹ Wang Jialin¹ Chen Gao² Li Daifang²

(1、Key Laboratory of Marine Geology, Tongji University, Shanghai 200092)

( 2、Jiangsu Oil Prospecting Bureau, Jiangdu, Jiangsu, 225261 )

Abstract: Meeting with the need of oil exploration, the integrated geophysics is studied in some coastal area in Jiangsu province. The integrated geophysical technology has been applied and finally the relationship of geological structure is revealed in this area.

18. 东海盆地海礁隆起新旧重力测线的拼接

陈华根 吴健生 王家林 陈冰

（同济大学 教育部海洋地质重点实验室,上海 200092）

Different Lines Integration with the Application

of Fuzzy Neural Net in Haijiao Uplift, East-China Sea

Chen Huagen Wu Jiansheng Wang Jialin Chen Bing

(Key Laboratory of Marine Geology, Tongji University, Shanghai 200092)

Abstract: In this paper, the lines in different period are integrated with the application of Fuzzy Neural Net. Compared with usual ways, it is proved that this is a better way to keep much more information, especially the part of high－frequency.

19. 我国多波束数据综合处理成图技术的现状和对策

金翔龙 高金耀 吴自银

（国家海洋局第二海洋研究所和海底科学重点实验室 杭州 310012）

Status and Strategy for Integrated

Processing and Charting Technique of Multibeam Data in China

Jin Xianglong，Gao Jinyao，Wu Ziyin

(2nd Institute of Oceanography & Key Lab of Submarine Geosciences, SOA, Hangzhou, 310012)

Abstract

Postprocessing and charting softwares combined with different multibeam sounding systems imported from Occident couldn’t accord with the demostic needs, especially for integrated processing and charting of various formats of multibeam data. The demostic users should adopt three kinds of compensatory methods: (1) Raw multibeam data are transformed into ASCII data, then processed by GIS; (2) DTM data formed by multibeam postprocessing softwares are decoded and changed into another format of DTM data adhering to user’s GIS; (3) Graphics mapped by multibeam postprocessing softwares are decorated by powerful graphics & image softwares. These makeshifts couldn’t adequately demonstrate advantages of electronic and digital cartography in accuracy, efficiency and quality, and they aren’t suitable enough for correction, collection and reapplication of various formats of multibeam data. Meanwhile, they are faced with specific difficulties of ocean-oriented cartography, for example, symbols, abbreviations and high resolution of coastlines in Chinese nautical charts. Those problems stated above are thoroughly solved in the PC Windows version of electronic mapping system for multibeam submarine topography MBChart , which has been independently developed by KLSG, SOA, to provide users an optimised technichal path between raw multibeam data and various applicational goals.

20.多波束海底地形电子成图系统MBChart的技术实现

高金耀 陶春辉 吴自银 方银霞 虞夏军

（国家海洋局第二海洋研究所和海底科学重点实验室 杭州 310012）

Technical Execution of

Electronic Mapping System for Multibeam Submarine Topography MBChart

Gao Jinyao，Tao Chunhui，Wu Ziyin，Fang Yinxia，Yu Xiajun

(2nd Institute of Oceanography & Key Lab of Submarine Geosciences, SOA, Hangzhou, 310012)

Abstract

Design and development of the PC Windows version of electronic mapping system for multibeam submarine topography MBChart are oriented to the management and application of various formats of raw multibeam data needed by different user. According to restriction of the PC memory, the standard data structure and optimized gridding strategy are developed for large groups of different multibeam systems. On the basis of absolutely self-reliant development, the techniques of GIS, database, OpenGL 3D graphics standard, object-oriented, Active X and VCL component are organically, synthetically applied to quarantee the developing efficiency and working stability of MBChart. MBChart is divided into three sub-systems: processing of multibeam data MBPro, managing of public database MBPub and mapping of submarine topography MBMap. As the main body of MBChart, MBMap can output 2D contour map, 2D contour-vectored color-filled map, 2D shading relief map and 3D lighting virtual map with agreement of certain national regulations for coordinate, projection, scale, symbol and label. MBPro provides the interface of raw multibeam and single beam sounding data for MBMap, and MBPub provides the interface of various space and attribute data from database for MBMap.