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由于实验室测试环境条件与深海海底的原位温压环境存在较大的差异,取样测量的沉积物声学参数通常偏离海底原位状态的真实值.该文利用深水型压载式沉积声学原位测量系统,在水深超过5000 m的西太平洋海域开展了沉积物声学原位测量试验,准确获取了深海底原位状态下沉积物的声速和声衰减系数,并同步采集了沉积物柱状样品.结果显示,实验室测量的沉积物声速、声衰减系数均高于原位测量结果.通过温压校正和数据—模型对比表明,实验室声速比与原位声速比存在较大的差异,难以通过温压校正模型和频散模型完全改正,这可能与深海沉积物的结构扰动有关.较之浅海沉积物,软弱的深海沉积物结构更易受到采样过程的扰动,因而深海沉积物的声学特性测量更为困难,这表明在深海海底声学研究采用原位测量技术具有必要性.该研究标志着我国海底声学研究由浅海走向深海,对推动海底声学的深入研究具有重要意义. 相似文献
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为了能够精确地测量海底表层沉积物的声学参数,自主研制了一种新型海底沉积物声学原位测量系统,与国内外传统的声学原位测量系统相比,该系统能够实时显示声波波形,调整测量参数,其工作方式除了站位式测量之外,还实现了拖行式连续测量,极大地提高了工作效率.根据前期海试情况,对海底仪器结构进行了重新设计,使之可以同时测量海底沉积物及海底海水的声学参数,同时建立了双向数字信道,解决了测量过程中系统信号的干扰问题.该系统的结构分为两部分:甲板控制单元和水下测量单元,整套系统通过主机控制程序进行控制,采用GPS定位系统测定仪器的大地坐标.为了检验系统的稳定性及准确性,分别进行了实验室水槽实验和海上试验.利用水声测量设备对测量系统进行实验室水槽标定分析,实验结果表明系统测量值相对误差仅为0.04%,测量结果具有较高的精度.海上试验在青岛胶州湾和东海海域进行,获得了试验区域海底沉积物声速和声衰减系数的测量数据,将测量数据与他人的研究结果进行对比分析,结果表明测量数据与前人研究结果一致,较为准确.该原位测量系统在站位式测量和拖行式测量中都能够快速准确地测量出沉积物声速和声衰减系数,可以作为海底底质声学测量的调查设备. 相似文献
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声学深拖作为一个声学设备搭载平台,主要功能是获取高分辨率的声学数据,精细刻画海底地形地貌特征以及浅层剖面结构,对于研究海底浅表层流体活动系统的类型、形成机制和演化模式有着重要作用.本文介绍的合成孔径声学深拖（Synthetic Aperture Sonar Deep-tow）搭载了合成孔径声呐、浅地层剖面仪以及多波束系统等声学设备,相比于传统的侧扫声呐,合成孔径声呐采用小物理孔径基阵通过信号处理虚拟合成大孔径基阵来获得方位向高分辨率,大大提高了测绘速率,同时结合高分辨率的浅地层剖面和多波束背散射数据,可实现海底浅表层特征的三维立体显示.为查明调查区海底浅层流体活动的声学特征,分析天然气水合物相关的流体渗漏活动性与浅层构造之间的关系,我们利用声学深拖对研究区进行了全覆盖的扫测,获得了高分辨率的合成孔径声呐图像、浅地层剖面资料以及多波束背散射数据,平面上识别出多个呈条带状的海底丘状体,火焰状的流体渗漏,新月形的麻坑构造等流体活动地质构造;浅层剖面上可见气体聚集的声学空白段落,凸起的活跃喷口,以及反射杂乱的柱状浑浊带.通过识别流体活动的特征,我们总结了浅层流体活动演化模式具有周期性：游离气体通过高渗透运移通道上升至海底,首先扩散聚集造成局部沉积物体积膨胀形成丘状体;然后受其各种外界因素影响丘状体崩塌而引起气体渗漏;最后流体逸散剥蚀海底松散沉积物而形成麻坑构造;随着流体排出,喷口重新闭合,流体在地层中再次聚集,聚集的气体又将沉积地层上拱,在麻坑底部又可能生成含气丘状体.海底浅表层蕴藏着丰富的地质信息,这对于研究海底复杂的流体活动有着重要意义. 相似文献
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We investigated the development of a distinct later phase observed at stations near the Japan Trench associated with shallow, outer-rise earthquakes off the coast of Sanriku, northern Japan based on the analysis of three-component broadband seismograms and FDM simulations of seismic wave propagation using a heterogeneous structural model of the Japan Trench subduction zone. Snapshots of seismic wave propagation obtained through these simulations clearly demonstrate the complicated seismic wavefield constructed by a coupling of the ocean acoustic waves and the Rayleigh waves propagating within seawater and below the sea bottom by multiple reflections associated with shallow subduction zone earthquakes. We demonstrated that the conversion to the Rayleigh wave from the coupled ocean acoustic waves and the Rayleigh wave as they propagate upward along the slope of seafloor near the coast is the primary cause of the arrival of the distinct later phase at the station near the coast. Through a sequence of simulations using different structural models of the Japan Trench subduction zone, we determined that the thick layer of seawater along the trench and the suddenly rising sea bottom onshore of the Japanese island are the major causes of the distinct later phase. The results of the present study indicate that for realistic modeling of seismic wave propagation from the subduction zone earthquakes, a high-resolution bathymetry model is very crucial, although most current simulations do not include a water column in their simulation models. 相似文献
5.
海底天然气渗漏是在海洋环境中广泛分布的自然现象.海底天然气渗漏可以指示沉积层中的烃类聚集带,渗漏出的大量气体（主要是甲烷）可能影响全球的气候变化,此外,与海底渗漏相关的浅层气改变了海底沉积物的土工性质,可能对海底工程构成威胁.因此海底渗漏研究意义重大.海底天然气渗漏不仅影响海底沉积物的物理性质,而且还极大地改变海底地形地貌,它能在海底形成麻坑、泥火山、冷泉碳酸盐岩以及化学自养生物群落等现象.在海底渗漏发生的地方,地形地貌特征可以在海洋测深和逆向散射数据上得到反映;沉积物的声学特征可以在地震剖面上得到反映,如形成声混浊、声空白、亮点、多次波、速度下拉等;有些渗漏在海面形成油渍膜,油渍膜可以在合成孔径雷达图像上得到反映.根据海底渗漏的上述地球物理特征,可以识别出可能渗漏区域,海底渗漏的证实需要用到海底观测和取样分析资料. 相似文献
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利用GAMIT软件,采用有基准算法对广东地壳运动观测网络新建成的广州基准站GZJZ的观测资料进行了归算,结果表明该基准站观测资料的质量是可靠的,并首次获得了该站在ITRF2000中毫米级精度的地心大地坐标。 相似文献
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本研究分析了2011年3月11日发生的Mw9.0日本东北地区太平洋近海地震对亚洲地区和韩国国内GPS卫星常年跟踪站的位移影响.为此,利用了日本东北地区太平洋近海地震发生前后两周(2011年3月4日到3月18日)的GPS站点数据,包括震中附近地区(韩国,中国,中国台湾地区,日本和俄罗斯)55个GPS卫星常年跟踪站和284个IGS 全球跟踪站,并采用GAMIT/GLOBK软件进行处理和平差,估算出所有GPS站点的同震形变.结果显示,日本东北地区太平洋近海地震引起的同震形变影响在亚洲地区比较明显,包括日本和附近国家,距离震中2702 km的中国武汉(WUHN)站也观测到同震形变.为精确分析日本东北地区太平洋近海地震对韩国国家大地控制网的影响,通过GAMIT/GLOBK软件计算出韩国GPS卫星常年跟踪站之间的基线长度变形,并分析出弹性变形量.结果表明:大部分GPS站点均向震中方向膨胀,且向震中的垂直方向收缩.由日本东北地区太平洋近海地震导致的最大剪应变达到韩国国家大地控制网年均变形率的约7倍,对韩国的地壳产生14.5~57.7 mm的水平位移,并导致韩国国家大地控制网产生弹性变形.因此,在不及时更新维护韩国国家大地控制网的情况下,GPS测量成果将会发生最大20 mm的位置误差. 相似文献
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深渊着陆器在下潜过程中,由于受到海流的影响,其坐底位置会偏离投放点,偏离量和偏离方向很难估计,而声学水下定位方法在深渊海区不太适用.通过在海面进行气枪十字放炮作业,利用炮点准确位置和时间信息,以及海底地震仪(Ocean Bottom Seismometer,OBS)记录的直达水波到时,对深渊着陆器的坐底位置进行精确测量可以提供有效定位数据.该方法对采集得到的数据进行预处理,使用蒙托卡洛方法结合最小二乘法,对万泉号着陆器实际坐底位置进行了反演校正,得到三个潜次的位置校正偏移量分别为211m、178m、861m,偏移方向各不相同,校正精度为±20m,比以往的定位精度大为提高.此外,该方法测量确定了三个海底标志物的精确位置,为未来万米无人或载人潜器提供了可靠的水下参考坐标. 相似文献
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The present study describes a new system designed and developed for observing crustal deformation on the sea floor. The system consists of two parts, the kinematic positioning by global positioning system (GPS) and acoustic ranging techniques. Since the location of a site at the ocean bottom relative to a reference site on land cannot be determined directly, the procedure was divided into two steps. First, the position of a vessel was determined using differential and kinematic GPS techniques, and then the position of a reference point at the ocean bottom was located relative to the vessel using the acoustic ranging technique. Thus, the location of the ocean-bottom station is determined relative to the reference sites on land in the global reference system. The accuracy was tested in several ways. In one experiment, a buoy was used as the surface station which linked the positions of a GPS receiver to the acoustic transponder. Assuming a simple sound velocity profile of the seawater, the position of an ocean-bottom reference point was estimated with an accuracy of several meters. Thus, with the present system, it is difficult to observe ocean-bottom crustal deformations generated by typical plate motions. Methods are being investigated to improve the observation system for more accurate sea floor positioning. 相似文献
11.
地球物理资料表明,莺歌海盆地区麻坑众多,浅层气发育,在高分辨率地震剖面上可以识别出到达海底的地震模糊带,在3.5 kHz的浅层剖面上可见穿透到海底的气体聚集带,在声呐图像可以识别出麻坑.莺歌海盆地不仅在其边缘隆起带沉积层较薄的地区存在海底天然气渗漏现象,而且在中央坳陷带沉积层巨厚的地区也存在海底天然气渗漏,海底天然气渗漏在莺歌海盆地是广泛分布的.莺歌海盆地广泛分布的海底天然气渗漏是全球海底天然气渗漏系统的重要组成部分,海底天然气渗漏系统排出的大量甲烷气体的一部分可能穿越水层到达海面. 相似文献
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瞬变电磁法在浅海工程勘探等领域受到了越来越多的关注.目前浅海瞬变电磁仍处于应用初期,相关研究少且未有成熟装备问世,有必要研究其探测能力并为观测系统选取最佳观测参数.本文以几种典型发射波形为例,采用褶积算法细致分析了不同发射波形条件下浅海瞬变电磁on-/off-time响应受海底介质电导率、磁导率及发射波形脉宽等参数的影响特征与规律;通过三维正演并设定极限探测深度阈值,进一步分析不同发射波形on-/offtime期间浅海瞬变电磁探测能力及对典型三维目标体的极限探测深度.基于本文研究成果,可为浅海瞬变电磁探测装置设计、观测系统的参数选取及试验参数的选取等提供了一些有价值的理论借鉴. 相似文献
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海洋地球物理以物理学的思维与方法研究占地球三分之二面积的海洋系统.20世纪地球科学迅猛发展,它的重大进展是海底扩张说与板块构造说的出现和海底大洋的发现,以及前者所引发的地球科学思想革命,从固定论向活动论的思维转变.海底研究对于20世纪地球科学发展的贡献极为巨大,而海洋地球物理是推动海底科学研究的重要原动力.海洋地球物理在20世纪地球科学的发展中有过辉煌的成就,占有十分重要的地位;在新的21世纪里,海洋地球物理研究仍然保持着前沿科学的地位,继续推动着地球科学的进展.目前的海底探测主要还是依赖于声学探测技术.水下声学定位技术是实现水下探测系统精确定位和海底高精度探测的基础.传统性的海洋地震探测技术是研究海底构造与海洋岩石圈深部结构和寻找海底矿产的主力技术,它近年来无论在海上采集技术还是数据处理技术方面都发展得很快.多波束测深、侧扫声呐测图和海底地层剖面测量等则是近数十年快速发展起来探测海底浅部结构信息的技术.这些技术已经在当代海底科学研究、海底资源勘查、海洋工程和海洋开发,以及海洋军事活动等方面发挥出极其重要的作用. 相似文献
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动校正是地震资料处理的关键内容之一,直接关系到地震资料处理结果的精度.在浅层和大偏移距情况下,常规动校正使波形发生拉伸畸变,波形拉长、频带向低频方向移动,进而影响叠加效果.通常地震资料处理中大都采用切除的方法克服动校正拉伸畸变的影响,这对目的层较深时是可取的.以工程地质调查为目的的海洋地震勘探旨在了解海底之下较浅地层深度范围内的地质信息,一般勘探区水深较浅,数据叠加道数较少,如果仍然采取切除处理,势必严重影响资料的分辨率和准确度.本文阐述了一种无拉伸动校正方法,能较好地解决动校正后的波形畸变问题,理论模型和实际资料的处理结果表明该方法在近海浅层工程地震勘探中是行之有效的,有助于提高速度分析的精度和地震资料的分辨率. 相似文献
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T. -T. Yu J. Fernndez C. -L. Tseng M. J. Sevilla V. Araa 《Journal of Volcanology and Geothermal Research》2000,103(1-4)
A 17-benchmark geodetic network in the volcanic area of the Teide Caldera, Canary Islands has been utilised several times since 1982 to detect crustal movements associated with volcanic activity within the network, as well as a procedure for solving configuration problems. The network is located on the mid-western side of the Caldera, where there are two different morphological zones that both have benchmarks. The authors performed a sensitivity test of this geodetic network for volcano monitoring purposes. To do so, we use a deformation model to calculate surface displacement caused by a dike intrusion in a homogenous half space. The depth and location of dike are changed to study the variation of the effects produced (displacements). The size and location of the intruded dike are found to play a major role in determining both the displacement pattern and magnitude. When the dike is close to the surface, there is an inversion of the surface displacement pattern and very large surface displacement at certain benchmarks. Such phenomena can serve as precursors of such dike eruptions. Our study show a clear need to extend the existing geodetic network to cover the full island for volcano monitoring purposes. 相似文献
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地球科学研究的新型观测平台——线缆式海底地震观测台（网）,是一种基于海底光电复合缆的光电传输技术,将传统的陆地地震观测台站向海区延伸、弥补海区地震观测台站的不足,实现实时、长期连续观测地球内部过程的新技术,目前已成为海洋科学的创新性研究平台,相关的技术方法也有了突飞猛进的进步.2018年,我国研发建设的"福建近海海底地震观测台",在前人探索研究的基础上,突破了线缆式海底地震观测台（网）关键技术,实现数据实时传输功能,具备进入地震行业网的能力.经过超过三个月的试运行检验,证实了系统的稳定性和可靠性.本文详细介绍了福建浯屿岛海底地震台（网）研发的关键技术与建设流程、关键技术环节相关规范和检测结果.地震采集数据结果表明,浯屿岛海底地震观测台实现了数据实时流服务,并可接入中国地震局JOPENS系统,数据实时传输正常,并自动存储实时波形数据;试运行期间以实际99%以上的高运行率,达到了国家测震台网管理规定的优秀标准.研发结果可为我国今后的海底地震观测台（网）建设提供重要参考指标与经验借鉴. 相似文献
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胜利油田滩浅海地区由于特殊的地表条件和复杂多变的表层结构，既不同于陆上勘探也不同于海上勘探，尤其在两栖地带存在海陆两种施工方式，如何在地震波激发和接收方面采取措施确保资料一致性，及优化观测系统设计以拼接好过渡带的地震资料是施工任务的关键.为此，依托中石化地震勘探重点基础研究实验室，在地震波的激发、接收和观测系统优化设计方面作了大量研究试验工作，形成了一套适用于滩浅海地区的地震勘探技术.通过冀东和垦东等地区应用联合表层调查和检波器精确定位等技术，有效地提高了地震资料的信噪比，改进了成像精度，取得了很好的地震勘探效果. 相似文献
18.
High-resolution seismic survey was conducted to investigate acoustic characteristics of gassy sediments along the southern shelf of the Sea of Marmara. The acoustic turbidity zones outlined within the study area are generally below 2–9 m (2-10 ms TWT) the seafloor whilst this vertical distance varies between 9 and 21 m (10–25 ms TWT) for acoustic blanket type reflections. The gassy sediments cover an area of sea floor of about 45, 110, and 75 km2 in front of Gönen River, Kocasu River, and Gemlik Bay, respectively. The gassy sediments in the center of Gemlik Bay exhibited an elliptical geometry similar to its basin while the others have deltaic forms in front of the rivers. The sea bottom and near surface sedimentary units are made-up of organic-rich sediments, mostly transported by the southern rivers. The gas observed in sediments is thought to be of biogenic origin, which may be caused by degradation of organic matter in the sediment. 相似文献
19.
Tian Li Yan Liu Xiao Cheng LunXi Ouyang XinQing Li JiPing Liu Mohammed Shokr FengMing Hui Jing Zhang JiaHong Wen 《中国科学:地球科学(英文版)》2017,60(4):697-706
Antarctic tabular icebergs are important active components in the ice sheet-ice shelf-ocean system. Seafloor topography is the key factor that affects the drifting and grounding of icebergs, but it has not been fully investigated. This study analyzes the impact of seafloor topography on the drifting and grounding of Antarctic tabular icebergs using Bedmap-2 datasets and iceberg route tracking data from Brigham Young University. The results highlight the following points. (1) The quantitative distributions of iceberg grounding events and the tracking points of grounded icebergs are mainly affected by iceberg draft and reach their peak values in sea water with depths between 200 m and 300 m. The peak tracking point number and linear velocity of free-drifting icebergs are found in the Antarctic Slope Front (water depth of approximately 500 m). (2) The area of possible grounding regions of small-scale icebergs calved from ice shelf fronts accounts for 28% of the sea area at water depths less than 2000 m outside the Antarctic coastline periphery (3.62 million km2). Their spatial distribution is mainly around East Antarctica and the Antarctic Peninsula. The area of possible grounding regions of large tabular icebergs with long axes larger than 18.5 km (in water depths of less than 800 m) accounts for 74% of the sea area. (3) The iceberg drifting velocity is positively correlated with ocean depth in areas where the depth is less than 2000 m (R=0.85, P<0.01). This result confirms the effect of water depth variations induced by seafloor topography fluctuations on iceberg drifting velocity. 相似文献
20.
Progress in technology for the 2005 height determination of Qomolangma Feng (Mt. Everest) 总被引：2，自引：0，他引：2
Qomolangma Feng——Mt. Everest (QF in shorter) is located in the east part of the China-Nepal boundary. QF is the highest mountain in China, also in the world. It lies in the collision zone along the boundary of Eurasian and Indian plates. It is one of focuses in geo- sciences study[1―7]. The northern slope area of the QF (QF area in shorter) is in Tibet, China, and the altitude of snow line in the QF area is around 6000 m. Spring in the QF area is March, April and May every year, a… 相似文献