共查询到19条相似文献，搜索用时 281 毫秒
1.
杜宾-沃森(Durbin-Watson, DW)检验是检验回归分析中残差一阶自相关性的一种方法,该方法广泛应用于计量经济学中。本文将DW统计量应用于一维大地电磁反演中,将DW统计量作为惩罚项加入大地电磁反演目标函数中,从而减弱实测大地电磁数据与反演模型响应之差(即残差)的自相关性,实现了基于DW统计量的大地电磁一维反演方法。通过两个层状模型合成数据反演和南黄海实测大地电磁资料反演验证了该方法的有效性,并与传统的高斯-牛顿反演方法进行了对比。反演结果表明本文反演方法对于高阻薄层具有更好的分辨能力。 相似文献
2.
本文利用海洋地震探测方法对速度、密度连续性发生变化的地层成像精度高的优点,提高海洋大地电磁(MT)反演空间分辨能力,提出速度约束的海洋MT聚焦反演方法,可以将OBS深部地震探测获得的速度结构模型作为先验信息引入到海洋MT反演目标函数的模型约束泛函中,对反演迭代过程中的电阻率模型施加速度结构约束。根据南黄海千里岩隆起区构建的速度-电阻率模型的反演测试表明,基于MGS聚焦稳定泛函的大地电磁反演方法可以得到高阻层以下的低阻层结构,速度约束下的海洋MT反演可以进一步提高对电阻率估计的精度：在速度约束信息准确的情况下,可以大幅提高海洋MT反演对电性结构的垂向分辨能力;当高速屏蔽层下不同地层波阻抗差异很小而影响速度模型精度时,该方法仍可利用速度梯度信息进行层位约束,提高相应层位识别能力。 相似文献
3.
《中国海洋大学学报(自然科学版)》2021,(6)
海洋可控源电磁法(Controlled-Source ElectroMagnetic, CSEM)对于油气储藏饱和度判别具有较高的敏感性,这为其用于油气储藏检测奠定了基础。但是海洋CSEM相较于地震勘探而言对异常体的垂向分辨率较低,这为海洋CSEM资料反演异常体垂向结构带来困难。由于测井数据具有垂向分辨率高的特点,蕴含丰富的电阻率和深度等信息,测井信息的引入可在一定程度上改善海洋CSEM资料垂向分辨率低的不足。将测井数据作为先验信息引入目标函数的模型加权矩阵中,引导反演的迭代方向,并根据测井信息对电阻率垂向变化区域进行局部细化,精细刻画细化区域的电阻率变化,进而提高海洋CSEM反演的垂向分辨率,逼近反演的最优解。在南黄海中部隆起区的应用中,对海洋CSEM实测数据进行测井约束反演,其结果表明,测井约束的海洋CSEM反演结果不仅呈现了地电断面的基本结构,而且还能突出垂向发生明显变化的层位,表现出较高的垂向分辨率。 相似文献
4.
如何确定海底多金属硫化物的空间分布并对其进行资源量评价至关重要。瞬变电磁法是陆地金属矿床勘探的重要手段,但海底的崎岖地形、硫化物的复杂结构以及不稳定的近底观测条件为瞬变电磁在海洋中的应用提出了挑战。为验证瞬变电磁方法对热液区硫化物的勘探应用潜力,本文采用了有限元方法,结合大西洋洋中脊TAG热液区实测地形数据和硫化物深部剖面进行三维正演模拟,通过对比仪器在不同位置、姿态、离底高度的正演模拟结果发现:重叠回线探测装置在离底高度小于60 m时,可以有效探测到TAG丘体的高电导率异常。海底复杂地形以及仪器拖曳方式都会对二次场早期响应产生干扰,同时仪器姿态变化也会改变所探测到的响应,这表明,应结合研究区域的海底地形、仪器海底定位以及姿态数据才能更好的对实测瞬变电磁数据进行合理解释。 相似文献
5.
为了进一步理解构造地质过程对弧后盆地热液活动及成矿作用的影响和控制,以实测和收集的多波束资料为基础,对冲绳海槽南部多个海底热液活动区的地形地貌特征进行了精细刻画。结合前人研究成果,从构造地质学的角度分析了热液区地形地貌的成因机制。结果表明,冲绳海槽南部热液区均为海底火山成因地貌,不同热液区的海底地貌分属于不同类型岩浆作用的产物:D海丘受岛弧和弧后盆地岩浆作用的双重影响,A海丘群由岛弧为主的多源岩浆作用产生,C海丘和B海丘群属于琉球火山岛弧,雨花海丘形成于造山期后地壳伸展导致的岩浆上涌。冲绳海槽中央地堑与琉球火山岛弧的交汇处有利于形成大规模岩浆和地热活动。琉球火山岛弧的岩浆活动存在时空迁移,与海槽构造演化过程中由分散式裂陷向中心式裂陷的转换有关。唐印热液区的存在表明台湾北火山带在槽底北缘及陆坡区仍具有较强的岩浆和地热活动性,是未来冲绳海槽南部海底热液调查的重要靶区之一。 相似文献
6.
海水是一种高电导率的流体,根据电磁感应定律,运动的海水切割地磁场会在海水中产生感应电流,从而产生感应电磁场。本文从麦克斯韦方程出发,推导出一维速度场海水运动感应电磁场偏微分方程,利用电磁场水平分量在海表面和海底面上的连续性条件,得到海水运动感应电磁场表达式,并编写了Fortran计算程序。计算了常速度海水运动感应电磁场,并与格林函数法计算结果进行了对比,两种方法的计算结果一致。计算了变速度(即海水运动速度随深度变化)海水运动感应电磁场,并讨论了海水运动周期和海底介质电导率对海水运动感应电磁场的影响。计算结果表明:海水运动周期和海底介质电导率对常速度海水运动和变速度海水运动感应电磁场都有影响,但影响程度不同。在本文所述模型和参数条件下,海水运动感应电场和感应磁场振幅分别可达6μV/m和10nT,这与海洋大地电磁响应的量级相当。因而在处理海洋大地电磁数据时,海水运动感应电磁响应是不可忽略的噪音干扰,需要采用必要的压制手段。 相似文献
7.
在过去的十几年中,海洋可控源电磁法的迅猛发展在油气勘探中起到了重要的作用。在浅海环境中,常见的两种可控源电磁法的数据采集系统采用海底基站式（Sea Bed Logging（SBL））,以及拖缆式（Towed Streamer electromagnetics（TSEM））两种模式。本文的研究目的是研究在不同水深条件下,两种数据采集系统的工作模式以及海水对其的影响。为了更好的比较两种数据采集方式,本文采用了三种不同的分析方法：一维敏感度模型,二维油藏敏感指数,Occam反演。一维敏感度模型能够迅速的给出结果,但是由于结果的信息量有限,不足以给定准确的结论。二维油藏敏感指数可以依据正演的结果快速的给定一个水深和油藏敏感度的关系。Occam反演方法用于对合成数据进行反演计算,估计地下介质电阻率参数。为了更好的评价反演结果,本文引入了横向电阻异常率（ATR）。通过对合成数据的反演结果的分析,本文得出以下结论：在浅水环境中,SBL和TSEM数据采集系统都可以提供较高的分辨率,对高电阻层有很好的敏感度。在深水环境中,SBL数据采集系统具有明显的优势。ATR对于反演的电阻率参数结果具有很好的评价作用。 相似文献
8.
X-波段雷达近海海浪频谱反演的神经网络模型 总被引：2，自引：1，他引：1
X-波段雷达作为国内海浪观测的一种新工具,在海浪频谱获取和有效波高反演方面仍存在较多问题.本文利用非线性回归方法,将现场实测浮标数据频谱和雷达一维图像谱分别与标准频谱模型进行拟合,发现浮标频谱和一维图像谱具有标准频谱的特征,能够较准确地获取相应的谱参数.提出了建立由雷达一维图像谱参数反演海浪频谱参数的神经网络模型,同时在模型中加入影像序列信噪比,进而反演有效波高,并将反演结果与现场实测数据和传统算法(建立影像序列信噪比与有效波高之间的线性回归方程)进行了对比,结果表明,获取谱参数的误差和反演有效波高的平均误差在20％以内,而传统算法计算有效波高平均误差在20％以上. 相似文献
9.
海洋CSEM法因其对海底高阻体反应灵敏,可用于探测和识别海底天然气水合物储层,然而,由于海底天然气水合物成因和成藏规律复杂,一些区域横向块状分布或是垂向多层分布的成藏模式加大了探测难度和成本,对于探测分辨能力也提出了更高的要求。为了在实际CSEM探测中进行高阻异常的现场快速评估,借鉴地震勘探共中心点道集的转换方式,将二维模型的海洋CSEM响应在CMP域单元内转换为一维模型的响应,进而实现二维模型CSEM资料在CMP域内的近似一维反演,针对不同电阻率模型讨论勘探参数对异常体分辨能力的影响。结果表明,海洋CSEM资料的CMP域反演对横向和纵向上相邻的水合物储集体具有一定的分辨能力,这为海洋CSEM法探测复杂成藏模式的水合物提供理论依据。 相似文献
10.
为了研究频率域2.5维非线性共轭梯度反演在海洋天然气水合物探测中的实际应用效果,利用美国Scripps研究所在South Hydrate海域采集的可控源电磁探测数据进行2.5维非线性共轭梯度反演计算,结合其他地球物理方法在同一海区的研究结果,综合分析2.5维反演计算的准确性和有效性。结果表明,非线性共轭梯度反演能够清晰地反映出该区域海底面以下1~2 km地层的电导率结构分布,其局部反演结果与地震反射、地震层序、测井分析结果基本一致,且对小尺寸异常、浅层高阻体分辨力较强,尤其在海洋天然气水合物探测方面具有较大潜力。 相似文献
11.
利用2014年3–4月北象海豹携带的自动温盐深仪（CTD-SRDL）在阿拉斯加湾东部陆坡海域上采集到的温盐剖面数据,分析了该海域逆温现象的空间分布和演变过程。结果显示,研究海域存在明显的逆温现象,逆温幅度和逆温厚度范围分别介于0.2~1.6?C和20~280 m之间,前者沿陆坡向北幅度逐渐增大,后者在50?~58?N间往北逐渐变厚,在58?N以北海域平均厚度较薄。3月25日至4月22日,逆温层处于衰退阶段。逆温层下界温度不断下降,逆温幅度呈变弱趋势,逆温厚度呈变薄趋势。一维扩散模型模拟结果表明,湍扩散作用下,观测期间海表受热导致混合层上部位温升高,但底部仍保持低温,因此逆温层上界温度变化并不明显。次表层由于具有强的位温梯度,湍扩散导致逆温层下界温度显著降低,是观测期间逆温衰退的主要原因。湍扩散作用导致次表层水体温盐属性趋于均匀,这一过程对于阿拉斯加湾逆温现象的形成及演变研究具有重要意义。 相似文献
12.
We report on a hexactinellid sponge new to science, Walteria demeterae sp. nov., which was collected from the northwestern Pacific seamounts at depths of 1271–1703 m. Its tubular and basiphytous body, extensive lateral processes, numerous oval lateral oscula which are irregularly situated in the body wall, the presence of microscleres with oxyoidal, discoidal and onychoidal outer ends, and the absence of anchorate discohexasters, indicate it belongs to the genus Walteria of family Euplectellidae, which is also supported by molecular phylogenetic evidence from 18S, 28S, 16S rRNA and cytochrome c oxidase subunit I (COI) gene sequences. The unique morphotype, which is structured by a thin and rigid framework of body wall and lateral processes consisting of diactins, characterizes it as a new species. Local aggregations of individuals of this new species coupled with their associated macrofauna in the Suda Seamount are reported, highlighting its functional significance in providing biogenic microhabitats in the deep sea. 相似文献
13.
Moo Hee Kang Hyun-Chul Han Hyesu Yun Gee Soo Kong Kyong O. Kim Youn Soo Lee 《Marine Geophysical Researches》2007,28(3):257-269
A seamount chain with an approximately WNW trend is observed in the northeastern Ulleung Basin. It has been argued that these
seamounts, including two islands called Ulleung and Dok islands, were formed by a hotspot process or by ridge related volcanism.
Many geological and geophysical studies have been done for all the seamounts and islands in the chain except Anyongbok Seamount,
which is close to the proposed spreading ridge. We first report morphological characteristics, sediment distribution patterns,
and the crustal thickness of Anyongbok Seamount using multibeam bathymetry data, seismic reflection profiles, and 3D gravity
modeling. The morphology of Anyongbok Seamount shows a cone shaped feature and is characterized by the development of many
flank cones and flank rift zones. The estimated surface volume is about 60 km3, and implies that the seamount is smaller than the other seamounts in the chain. No sediments have been observed on the seamount
except the lower slope, which is covered by more than 1,000 m of strata. The crustal structure obtained from a 3D gravity
modeling (GFR = 3.11, SD 3.82 = mGal) suggests that the seamount was formed around the boundary of the Ulleung Plateau and
the Ulleung Basin, and the estimated crustal thickness is about 20 km, which is a little thicker than other nearby seamounts
distributed along the northeastern boundary of the Ulleung Basin. This significant crustal thickness also implies that Anyongbok
Seamount might not be related to ridge volcanism. 相似文献
14.
在海底地震仪(ocean bottom seismometer, OBS)广角地震记录剖面上, 经常可以见到震相清晰且连续的多次波信号, 多次波和初至波是由相同的震源信号产生的, 也是地壳真实结构的反映。但是在通常的OBS数据处理过程中, 经常将多次波作为无效信号剔除掉, 对其属性及应用的研究比较少。文章通过对台湾海峡南部OBS探测测线HXN01数据的处理, 对多个台站记录到的二次震相进行了识别与拾取, 并以OBS0106台站为例, 对识别出的二次Ps震相进行了系统的研究分析, 发现二次Ps震相的波形特征和质点运动轨迹与初至震相相似, 但波形最大振幅值明显大于初至震相。通过Rayinvr射线追踪方法模拟, 确定了二次Ps震相的主要反射层, 并发现加入二次震相后, 台站下方浅部沉积层射线覆盖密度有显著提升, 射线覆盖的区域也明显增加, 为沉积层精细结构的反演提供了更为丰富的数据基础。另外, 对理论模型的地壳结构进行加入二次Ps震相前后的反演测试, 结果显示加入二次Ps震相数据后, 沉积层的界面深度误差得到明显的改善。 相似文献
15.
Siderius M. Snellen M. Simons D.G. Onken R. 《Oceanic Engineering, IEEE Journal of》2000,25(3):364-386
In October 1997, the EnVerse 97 shallow-water acoustic experiments were jointly conducted by SACLANT Centre, TNO-FEL, and DERA off the coast of Sicily, Italy. The primary goal of the experiments was to determine the sea-bed properties through inversion of acoustic data. Using a towed source, the inversion method is tested at different source/receiver separations in an area with a range-dependent bottom. The sources transmitted over a broadband of frequencies (90-600 Hz) and the signals were measured on a vertical array of hydrophones. The acoustic data were continuously collected as the range between the source and receiving array varied from 0.5 to 6 km. An extensive seismic survey was conducted along the track providing supporting information about the layered structure of the bottom as well as layer compressional sound speeds. The oceanic conditions were assessed using current meters, satellite remote sensing, wave height measurements, and casts for determining conductivity and temperature as a function of water depth. Geoacoustic inversion results taken at different source/receiver ranges show sea-bed properties consistent with the range-dependent features observed in the seismic survey data. These results indicate that shallow-water bottom properties may be estimated over large areas using a towed source fixed receiver configuration 相似文献
16.
《Deep Sea Research Part I: Oceanographic Research Papers》2001,48(5):1309-1324
Rose-Bengal-stained benthic foraminifera in six pilot-core samples and one multicore sample collected from the Hess Rise and Suiko Seamount in August 1994 were studied in order to understand foraminiferal distributions between two areas divided by an oceanic front in the central North Pacific. Samples from the Hess Rise were collected in depths of 2167–3354 m under the warm, saline Kuroshio Extension, while samples from Suiko Seamount came from depths of 1811–1955 m under the cold, less-saline subarctic current. Sediment-trap results for the year prior to our sediment sampling show that organic matter fluxes were about 2.5 times greater at Suiko Seamount than at the Hess Rise. However, the hydrographic structure between 1800 and 3400 m, based on CTD observations, is almost the same at both sites. Temperature decreases from 2.2 to 1.7°C over the depth range of 1800–3400 m, salinity increases from 34.5 to 34.7, and the dissolved oxygen content gradually increases from 1.5 to 3.0 ml l−1. The faunal populations at the Hess Rise are quite different from those at Suiko Seamount. The abundant species at the Hess Rise are Epistominella exigua, Brizalina pacifica, Fursenkoina cedrosensis and Alabaminella weddellensis. These species characteristically inhabit phytodetrital aggregates deposited on an oligotrophic seafloor. The populations at Suiko Seamount are dominated by Triloculina frigida, Lagenammina cf. arenulata, Reophax subfusiformis, and Reophax scorpiurus. The reason for differences between these populations is unclear. However, the typical phytodetritus-dwelling species E. exigua is dominant at the Hess Rise, which is located in a subtropical area that has a pulsed supply of settling organic matter in the spring. On the other hand, E. exigua is rare at Suiko Seamount, a subarctic site where there are more stable and greater fluxes of organic matter in summer and autumn. Occurrences of this species may be related to the seasonally short supply of organic matter that reaches the seafloor in the oceanic North Pacific. 相似文献
17.
This paper describes observations of the velocity field over and near Cobb Seamount, a shallow seamount near the bifurcation of the Subarctic Current into the California Current in the northeast Pacific Ocean. The background flow field is examined with surface drifter data acquired as part of the WOCE Surface Velocity Program. The likelihood that a Taylor Cap circulation will be observed at Cobb is then estimated. The actual circulation at Cobb is examined with current meters deployed on three separate visits to the site and surveys of the velocity field carried out using an RDI acoustic Doppler current profiler. The observations indicate that a recirculation around the seamount does exist but not fit well with the theory of formation of a stratified Taylor column. A divergent bottom Ekman layer is also observed, which might have important implications for the trapping and retention of fish larvae near Cobb Seamount. 相似文献
18.
19.
基于Chirp数据和Biot-Stoll模型反演南海北部陆坡海底表层沉积物物理性质 总被引：1，自引：1，他引：0
浅地层剖面是基于声学信号(频率在几百至几千赫兹)在沉积物中的传播得到可反映沉积地层结构的数据，海底反射系数与沉积物物理性质密切相关。Biot-Stoll声波传播理论模型可以预测海底沉积物的物理性质，构建反射系数等声学参数与物理参数之间的关系，但在不同的海域采用不同的参数所获得的效果不同。为此，本文基于南海北部陆坡海底表层沉积物的实测物理参数，利用Biot-Stoll模型建立研究区海底反射系数和沉积物物理性质之间的关系，结果表明模型计算值与样品实测值吻合度总体较好，偏差在0.1%～4.9%之间，并建立了频率3.5 kHz时海底反射系数与沉积物孔隙度、密度、平均粒径之间的关系方程，且方程拟合度较高，可决系数R2均大于0.99。在对典型Chirp剖面数据计算其海底反射系数的基础上，反演了海底表层沉积物的孔隙度、密度、颗粒平均粒径等物理性质，其中反演孔隙度、密度、平均粒径与实测孔隙度、密度、平均粒径相对误差均小于5%，结果与实测值基本相符，表明该反演方法在南海北部陆坡区的应用是可行的。 相似文献