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1.
分析研究了南海北部大陆架西南缘的海南岛东南外海海底沉积物声学物理特性,在多个航次中进行了海底沉积层取样、海水CTD测量、浅地层及旁侧声呐扫测等工作.在实验室里对沉积物样品进行声学参数、沉积学基本参数、物理力学参数和14C年龄测试等分析.根据多尔特曼公式求解出弹性模量、体积弹性模量、压缩系数、切变模量、泊松比和拉梅常数等六项沉积物弹性参数.分析结果表明在该海区海底沉积物的压缩波速为1.474~1.700 m/s,在不同的海区内有高低声速两类性质的沉积物分布;沉积物的切变波速为150~600 m/s;沉积物在100 kHz的声衰减为35~260 dB/m;沉积物的密度为1.4~2.0 g/cm3;沉积物的孔隙度为42%~88%. 相似文献
2.
海底沉积物纵波波速与物理-力学性质的理论关系和比较 总被引：3，自引：1，他引：2
本文提出以密度变化比和等效弹性模量变化比为参数描述海底沉积物纵波波速,得到密度变化比是由孔隙率、海水密度和海底沉积物固相密度构成的复合参数,建立了以复合参数和等效弹性模量变化比为变量的泰勒多项式海底沉积物纵波波速公式。基于单因素分析法得出纵波波速可表示为参考声速与调制函数的乘积,沉积物的参考声速由海底底质物理性质确定,建立了复合参数-声速的近似理论模型。对该理论模型与现有的主要纵波波速经验公式的分析结果表明,孔隙率-纵波波速经验公式只是参考声速不同,但调制函数是互相等效的,验证了本文海底沉积物纵波波速理论关系的有效性。 相似文献
3.
对南海某海域深度100～400 m的海底浅层（约2 m埋深范围）沉积物柱状样在接近海底水压力下进行三轴应变-声学同步测量,结果表明沉积物纵波声速有两个特征:（1）从应变过程开始到结束,沉积物纵波声速不断变化;（2）平均声速随着平均静弹性模量的增加,由大变小又由小变大,存在声速最小值。这些结果与海底浅表层沉积物的物理力学性质、围压、颗粒的结合状态改变有关。此外,沉积物动弹性模量和孔隙度呈良好的负相关性,这与孔隙度增大含水量增大有关;动弹性模量是静弹性模量的10～100倍,这主要与三轴应变试验的应变数量级与声波振动产生的应变数量级的差异大有关。采用本论文实验测量的数据分别建立了双复合参数-声速和孔隙度-声速经验公式,分析结果表明双复合参数-声速公式声速预报误差约是孔隙度-声速公式的1/4,表明双复合参数-声速公式更加有效。 相似文献
4.
基于主元分析技术的海底沉积物声速预报方程 总被引：2，自引：0，他引：2
通过应用主元分析技术建立预报海底沉积物声速的经验方程，将前人研究报道的经验方程进行分析研究，指出其计算误差，运用南海南部大陆架和大陆坡数据，建立了主元回归计算模型。从理论上研究了如何在众多影响声速的物理参数中，排除相互关联的参数，优选出相互独立的、且对声速有显著影响的少数几个物理参数，用优选后的物理参数建立了南海南部海域大陆架及大陆坡沉积物的3参数（孔隙度n、颗粒中值粒径Ma、塑限W，）声速预报方程：Cp=1774-5．0944n＋12．499Md＋0．9985Wp，该方程的相对预报误差仅为-4．48％-3．77％。 相似文献
5.
基于海底表层沉积物声速特征的南海地声模型 总被引：1，自引：1，他引：0
在由垂直声速梯度建立的地声模型基础上,通过引入沉积物与海水声速比和沉积物压缩波与切变波声速比两个表征沉积物声学特征参数得到更全面和有实际指导意义的地声模型。在沉积物声波传播FCMCM模型基础上,基于热作用和重力作用下沉积物两相介质的应力应变分析,建立TFCMCM和DFCFCM模型,运用模型校正表层沉积物声速特征来计算和解释地声模型。根据海底表层沉积物存在低声速和高声速两种类型,结合沉积物沿纵深孔隙度不变和变化两种类型,得到南海海底沉积物的两类四种典型地声模型:低声速孔隙度不变型、低声速孔隙度减小型、高声速不变型和高声速孔隙度减小型。运用这四种典型地声模型的组合解释了卢博提出的南海三种典型声速结构。认知声速结构将为南海声学探测海底、划分海底区域提供模型支持。 相似文献
6.
南海北部大陆架海底沉积物物理性质研究 总被引：6，自引：0，他引：6
用物理(声学的、工程地质的、扫描电子显微镜)等技术方法，综合分析了沉积物结构特征和工程力学性质，研究了颗粒接触、堆垒、孔隙等现象与物理性质之间的关系，得出了沉积物声学物理参数和应力一应变性质之间的关系。结果表明，南海北部大陆架海底沉积物有6种结构类型，其中混合接触结构类型的沉积物具有较高的抗压强度和声速，浅层海底存在着高、低声速分层的中尺度结构。 相似文献
7.
海底沉积物声学物理力学性质聚类分析研究 总被引：1，自引：1，他引：0
Stoll、Hamilton等分别从理论和实测方面出发研究海底沉积物声学与物理力学性质关系,这两类研究都是将声学性质作为独立性质从沉积物的物理性质中提取出来,以两者作为因果关系进行研究,割裂了其内在统一性.本文不试图建立声学与物理力学性质的经验方程,而是综合考虑海底沉积物声学、物理力学性质,对南海大陆坡和人陆架沉积物进行聚类研究,分析南海海底沉积物共有的性质.研究表明聚类分析方法为海底沉积物性质研究提供了一种有效的分类手段,通过聚类,得出如下结论:(1)声速与孔隙度、密度等物理力学性质存在着明显的单调相关性,可以通过某些物理力学参数来预报沉积物的声速,同时可以通过测量沉积物声速反演沉积物的某些物理力学参数;(2)海底沉积物的声速和地文单元、沉积物的颗粒成份组成有关;(3)火陆坡黏土质粉砂、粉砂、砂质粉砂和大陆架粉砂、砂质粉砂、粉砂质砂的压缩波速依次增大,切变波速依次减小;(4)海底沉积物声学与物理力学性质聚类分析研究,可以作为海底沉积物的声学探测的参考依据. 相似文献
8.
中国黄海、东海和南海北部海底浅层沉积物声学物理性质之比较 总被引：13，自引：0，他引：13
黄海、东海和南海北部海底沉积物声学物理性质存在着差异,这与海区海底地质和沉积环境有关。取样所及的海底沉积物样品分析表明:黄海实验海区海底有6种沉积类型,东海实验海区海底有3种沉积类型,南海北部大陆架海区海底有6种沉积类型。三个海区的沉积物密度为1.48～2.03g·cm-3;沉积物含水量为10%～90%;沉积物孔隙度为65%～80%;沉积物纵波声速为1460～1916m·s-1;沉积物横波声速为115～611m·s-1。 相似文献
9.
比较国内外主要研究者提出的海底沉积物声速单参数、双参数和多参数预报经验方程的物理意义和适用性,提出了孔隙度-含水量预报海底沉积物声速新的双参数公式,该式避免了单一参数预报声速经验方程和某些双参数公式中物理意义不明确以及多参数方程复杂性及对提高预报计算能力效果不显著之处.基于理论分析,改进孔隙度-含水量双参数计算公式得到的通用模型具有明确的物理意义,可以通过修改参数适用于不同海域的声速预报,提高了泛化能力,扩大了适用范围.通过对孔隙度、含水量等物理参数的权值分析研究,更加明确了孔隙度是影响海底沉积物声速大小的最关键参数.用台湾海峡北部、南海海域、珠江口大陆架三处的海域沉积物测量数据比较了不同模型,验证了本模型的优越性. 相似文献
10.
为研究深海海底沉积物声学特性与物理性质相关关系,于2016年11月在实验室对水深3164～5 592 m的菲律宾海深海海底沉积物柱状样品的声学特性进行测量,获取了沉积物声速、声速比、声阻抗、声阻抗指数等声学特性参数。结合沉积物的孔隙度和密度等物理性质参数,分析了海底沉积物声速、声速比、声阻抗、声阻抗指数与孔隙度、密度的相关关系,建立了该海域海底沉积物声学特性回归方程。研究结果表明:研究区深海数据与浅海回归方程符合度较差,与深海回归方程符合度较好;Hamilton校正方法有助于修正实验室测量引起的温度和压力误差,声速比与Hamilton方程符合度比声速好;声阻抗和声阻抗指数与物理性质参数的相关性优于声速和声速比。此外,研究认为由于海底沉积物的沉积环境较为复杂,其声学特性回归方程存在差异。由于上述差异的存在,在使用基于不同海域数据建立的回归方程进行海底沉积物声学特性预测时,应加以区别对待。该研究丰富了深海海底沉积物声学数据,对促进深海海底沉积物声学深入研究具有一定的借鉴意义。 相似文献
11.
Coastal inundation associated with extreme sea levels is the main factor which leads to the loss of life and property whenever a severe tropical cyclonic storm hits the Indian coasts. The Andhra and Orissa coasts are most vulnerable for coastal inundation due to extreme rise in sea levels associated with tropical cyclones. Loss of life may be minimized if extreme sea levels and associated coastal flooding is predicted well in advance. Keeping this in view, location specific coastal inundation models are developed and applied for the Andhra and Orissa coasts of India. Several numerical experiments are carried out using the data of past severe cyclones that struck these regions. The simulated inland inundation distances are found to be in general agreement with the reported flooding. 相似文献
12.
This study tests the hypothesis that the in situ void ratio of surficial marine sediments may be predicted from shear wave velocity-depth data with a reliability equal to that of other methods currently available. Shear wave velocity is fundamentally controlled by the number of grain-to-grain contacts per unit volume of material and by the effective stress across those contacts. In this study, three previously established empirical formulae are used to predict void ratio from velocity-depth data. Field data were acquired along a transect off the northern Californian coast across which water depth increased from 35 to 70 m and seafloor sediment type varied from sand to silty-sand, respectively. A towed seafloor sled device was used to collect shear wave refraction data, and a marked, systematic decrease in velocity was observed along the line, ranging from 35-70 m/s for the coarse, near-shore material to 25-40 m/s for the finer, offshore deposits. Void ratios predicted from these velocities were compared with data measured directly from box-core samples. Of the formulae used for prediction, two agree remarkably well with the control data. Both predicted and control values increase from 0.6-0.8 for the sandy material to 1.1-1.5 for the silty-sand. Thus, this study does not disprove the hypothesis set and demonstrates the potential of field shear wave velocity-depth data as a means of delineating spatial variation in void ratio for surficial marine sediments in a remote, nondestructive manner. 相似文献
13.
Hoi-Soo Jung Kap-Sik Jeong Yong-Shik Chu Sung-Hyun Park Ki-Hyune Kim 《Marine Georesources & Geotechnology》2001,19(3):181-195
Grain size and water content in box-core sediments from the Clarion-Clipperton fracture zone (C-C zone) in the northeast equatorial Pacific were analyzed in detail to understand the downcore variations across a hiatus between Quaternary and Tertiary layers. Grain-size distributions in the topmost core sediments show two modes: a coarse mode (peaked at 50 μm) and a fine mode (at 2-25 μm). The coarse mode disappears gradually with depth accompanied by the dissolution of siliceous fossil tests, whereas the fine mode coarsens due to the formation of authigenic minerals. Water content increases abruptly across a color boundary between an upper pale brown layer and a lower dark brown layer that is the hiatus between Quaternary and Tertiary layers. Abundant smectites and microvoid molds, which are created by the prolonged fossil dissolution in the underlying sediment, are attributed for the abrupt downcore variation of water content. Overall variations in grain size and water content in the topmost core sediments in the western C-C zone are possibly constrained by the dissolution of biogenic siliceous fossils. Variations in geotechnical properties related to these changes must be considered in the design of nodule collectors. 相似文献
14.
Shigehisa Nakamura 《Marine Geodesy》2001,24(1):27-33
This article concerns an interrelation between the sea levels and the western boundary flow near a tectonic boundary in a local zone in the Northwestern Pacific. In this zone, sea level variations at stations located on the coast facing the Pacific are studied to find the interrelation between variations of the Kurosio flow as an index of the distance of the flow axis off a specific coast. The result is discussed after data processing of the monthly means of the sea levels, and a notice is taken of variations caused by active crustal upheavals during a seismic event, a local earthquake. 相似文献
15.
Particulate samples were collected from the Changjiang river system during a flood period, in May 1997, and POC, stable isotope and lipids associated with particles were examined. Results showed the decrease (0.84% ～ 1.88%) of organic carbon content from the upper reaches to the estuary.δ13C values of particulate organic carbon was in the range of -24.9×10-3 to -26.6×10-3, which were close to the isotopic signature of continental C3 vegetation. Total particulate n-alkanes concentrations varied from 1.4 to 10.1μg/dm3,or from 23.7 to 107μg/g of total suspended matter. Fatty acids were present in all the samples, from 1.4 to 5.4μg/dm3, with saturated and unsaturated straight-chain and branched compounds in the carbon number range from C12 to C30. Both δ13C and the ratio of carbon content to nitrogen content indicate the predominance of terrestrial inputs (soil organic matter) among the particles. The biomarker approach has been used to identify the relative portion of terrigenous and autochthonous fraction in the particulate samples. The distribution of fatty acids suggests a striking phytoplanktonic and microbial signal in most particle samples. The terrestrial alkanes are used to estimate the contribution of terrestrial inputs along the mainstream. 相似文献
16.
Andrzej Chybicki 《Marine Geodesy》2018,41(1):1-23
Current trends of development of satellite derived bathymetry (SDB) models rely on applying calibration techniques including analytical approaches, neuro-fuzzy systems, regression optimization and others. In most of the cases, the SDB models are calibrated and verified for test sites, that provide favorable conditions for the remote derivation of bathymetry such as high water clarity, homogenous bottom type, low amount of sediment in the water and other factors. In this paper, a novel 3-dimensional geographical weighted regression (3GWR) SDB technique is presented, it binds together methods already presented in other studies, the geographically weighted local regression (GWR) model, with depth dependent inverse optimization. The proposed SDB model was calibrated and verified on a relatively difficult test site of the South Baltic near-shore areas with the use of multispectral observations acquired by a recently launched Sentinel-2 satellite observation system. By conducted experiments, it was shown that the proposed SDB model is capable of obtaining satisfactory results of RMSE ranging from 0.88 to 1.23[m] depending on the observation and can derive bathymetry for depths up to 12m. It was also shown, that the proposed approach may be used operationally, for instance, in the continuous assessment of temporal bathymetry changes, for areas important in the context of ensuring local maritime safety. 相似文献
17.
N. H. Khadge 《Marine Georesources & Geotechnology》2000,18(3):251-258
As a part of the environmental impact assessment studies, geotechnical properties of sediments were determined in the Central Indian Basin. The undrained shear strength and index properties of the siliceous sediments were determined on 20 box cores of uniform dimension collected from various locations in five preselected sites. The maximum core length encountered was 41 cm and most of the sediments were siliceous oozes consisting of radiolarian or diatomaceous tests. The shear strength measurements revealed that surface sediments deposited in recent times (0-10 cm) have a shear strength of 0-1 kPa; this value increases with depth, reaching 10 kPa at 40 cm deep. Older sediments have greater strength because of compaction. Water content varies in the wide range of 312-577% and decreases with depth. The clay minerals such as smectite and illite are dominant and show some control over water content. Wet density, specific gravity, and porosity do not indicate any notable variation with depth, thereby indicating a uniform, slow rate of sedimentation. The average porosity of sediments is 90.2%, specific gravity 2.18, and wet bulk density 1.12 g/cm 3 . Sediments exhibit medium to high plasticity characteristics, with the average plasticity index varying between 105% and 136%. Preliminary studies on postdisturbance samples showed an increase in natural water content and a decrease in undrained shear strength of sediments in the top 10- to 15-cm layer. 相似文献
18.
An Improved Calibration of Satellite Altimetric Heights Using Tide Gauge Sea Levels with Adjustment for Land Motion 总被引：2，自引：0，他引：2
Gary T. Mitchum 《Marine Geodesy》2000,23(3):145-166
Several major improvements to an existing method for calibrating satellite altimeters using tide gauge data are described. The calibration is in the sense of monitoring and correcting temporal drift in the altimetric time series, which is essential in efforts to use the altimetric data for especially demanding applications. Examples include the determination of the rate of change of global mean sea level and the study of the relatively subtle, but climatically important, decadal variations in basin scale sea levels. The improvements are to the method described by Mitchum (1998a), and the modifications are of two basic types. First, since the method depends on the cancellation of true ocean signals by differencing the altimetric data from the tide gauge sea level time series, improvements are made that produce a more complete removal of the ocean signals that comprise the noise for the altimetric drift estimation problem. Second, a major error source in the tide gauge data, namely land motion, is explicitly addressed and corrections are developed that incorporate space-based geodetic data (continuous GPS and DORIS measurements). The long-term solution, having such geodetic measurements available at all the tide gauges, is not yet a reality, so an interim solution is developed. The improved method is applied to the TOPEX altimetric data. The Side A data (August 1992?February 1999) are found to have a linear drift component of 0.55 + / 0.39 mm/yr, but there is also a significant quadratic component to the drift that is presently unexplained. The TOPEX Side B altimeter is estimated to be biased by 7.0 + / 0.7 mm relative to the Side A altimeter based on an analysis of the first 350 days of Side B data. 相似文献
19.
Extreme sea levels associated with severe cyclonic storms are common occurrences along the east coast of India. The coastal districts of Orissa have experienced major surges in the past. The recent Paradip super cyclone is one of the most severe cyclones, causing extensive damage to property and loss of lives. Extreme sea levels are major causes for coastal flooding in this region. Damages can be minimized if the extreme sea levels are forecast well in advance. In the present study, we develop a location specific, fine resolution model for the Orissa coast on the lines similar to that of IIT-D storm surge model (Dube et al. 1994). The model runs on a personal computer. The bathymetry for the model is extracted from very fine resolution naval hydrographic charts for the region extending from the south of Orissa to south of West Bengal. A simple drying scheme has also been included in the model in order to avoid the exposure of land near the coast due to strong negative sea surface elevations. An attempt was made in this study to simulate extreme sea levels along the Orissa coast using the data of past severe cyclones. The model results reported in the present study are in good agreement with available observations or estimates. 相似文献
20.
The continental margin of northern Sinai and Israel, up to Haifa Bay, is the northeastern limb of the submarine Nile Delta Cone. It is made up predominantly of clastics from the Nile and its predecessors. The continental shelf and coastal plain of Israel are built of a series of shore-parallel ridges composed of carbonate-cemented quartz sandstone (locally named kurkar), a lithification product of windblown sands that were piled up into dunes during the Pleistocene. The drop in global sea level and regression during the last glacial period exposed the continental shelf to subaerial erosion and created a widespread regional erosional unconformity which is expressed as a prominent seismic reflector at the top of the kurkar layers. The subsequent Holocene transgression abraded much of the westernmost kurkar ridges, drowned their cores, and covered the previous lowstand deposits with marine sands, which were in turn covered by a sequence of sub-Recent clayey silts. The Mediterranean coasts of Sinai and Israel are part of the Nile littoral cell. Since the building of the Aswan dams the sand supplied to Israel's coastal system is derived mainly from erosion of the Nile Delta and from sands offshore Egypt that are stirred up by storm waves. The sands are transported by longshore and offshore currents along the coasts of northern Sinai and Israel. Their volume gradually declines northward with distance from their Nile source. The longshore transport terminates in Haifa Bay where some sand is trapped, and the test escapes to deeper water by bottom currents and through submarine canyons, thus denying Nile-derived sand supply to the 40-km-long 'Akko-Rosh Haniqra shelf. The sand balance along Israel's coastal zone is a product of natural processes and human intervention. Losses due to the outgoing longshore transport, seaward escape, and landward wind transport exceed the natural gains from the incoming longshore transport and the abrasion of the coastal cliffs. The deficit is aggravated by the construction of (1) seaward-projecting structures that trap sands on the upstream side and (2) offshore detached breakwaters that trap sands between themselves and the coast. The negative sand balance is manifested by the removal of sand from the seabed and the consequent exposure of archaeological remains that were hitherto protected by it. The sediments that escape seaward from the longshore transport system form a 2.5- to 4-km-wide sandy apron adjacent to the shore that extends to where the water is 30 - 40 m deep. The apron's slope (0.5 - 0.8) is steeper than the theoretical equilibrium slope for the median grain-size diameter in this zone (0.1 - 0.3 mm). The beach sands and the apron's surficial sands are well sorted. Their grain size decreases with distance from shore, from 0.2 - 0.3 mm nearshore to 0.11 - 0.16 mm by the drowned ridge. The coarse-grained fraction consists of skeletal debris (commonly 5 - 12% carbonate matter) and wave-milled kurkar grains (locally named zifzif). In deeper water, the basal sands underlying the fine-grained sediment cover consist of 1- to 30-cm layers whose composition ranges from silty sands to various types of sands (fine, medium, coarse, and gravelly) to zifzif. For the most part, they contain large amounts of skeletal debris (20 - 60%) and small fragments of kurkar. Two types of kurkar rock were encountered offshore: a well-sorted, fine- to medium-grained (0.074 - 0.300 mm) lithified dune sand with variable amounts of carbonate cement, ranging from hard rock of low permeability to loose sand; and a porous sandstone made up predominantly of algal grains and skeletal debris (calcarenite). 相似文献