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主动源海底地震仪探测在海底结构的研究中发挥着重要作用, 其中转换横波数据模拟为研究海底构造和物质属性提供了精确依据。本文针对现行转换横波模拟技术存在的步骤繁琐、难以确保最优解和无法进行非唯一性分析等问题进行研究, 提出了基于模型解空间和目标函数的模拟技术, 形成了主动源转换横波数据模拟的新方法, 该方法可借助计算机程序实现结构模拟的自动化。在南海西北陆缘的西沙地块OBS2013-3测线上对该方法进行验证, 分别利用单台PPS震相和全体台站的PSS震相走时数据进行模拟试验。结果表明, 本文的方法能够提供对于最优模型的快速、准确搜索和非唯一性范围的估计。这一方法有助于提高主动源海底地震仪转换横波数据模拟的效率, 并为结果的可靠性和稳定性提供更好的保障。 相似文献
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《热带海洋学报》2016,(1)
通过挖掘海底地震仪记录的转换横波信息,可以促进对地壳岩性、均质性的认识。以南海南沙地块OBS973-1剖面上18个台站的数据为实例,阐明了海底地震仪横波震相识别的方法。首先对三分量OBS(Ocean Bottom Seismometer)地震数据进行带通滤波、维纳滤波、极化滤波等去噪处理,然后利用能量扫描法求得极化角进行水平分量坐标旋转,求取最佳径向分量。数据处理结果表明,相对于OBS记录的磁罗盘方位角,能量扫描法求取的极化角更为准确可靠。最后通过OBS973-1地震剖面垂直分量与径向分量上的纵横波走时对比、质点运动轨迹、速度模型试算等手段,进一步确定了转换横波震相的类别。在南沙地块OBS探测中成功地在10个台站中识别出了PgSs、PnSc、Pms等震相,不仅可以为下一步横波速度结构模拟提供坚实的数据基础,而且可以为今后OBS转换横波在其他地区的有效应用与推广提供借鉴。 相似文献
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2015—2018年, 国家自然科学基金重大研究计划“南海深海过程演变”的重点支持项目“南海东部马尼拉俯冲带深部结构探测与研究”以马尼拉俯冲带为研究重点, 从深部地球物理的角度探索南海形成演化史与运行规律。项目执行期间, 在国家基金委共享航次协助下, 先后开展和参与5次综合地球物理探测, 共投放海底地震仪(Ocean Bottom Seismometer, OBS)台站73台次, 海底电磁仪(Ocean Bottom ElectroMagnetometers, OBEM)仪器5台次, 累积放炮达13872炮, 成功获得了60台OBS数据和5台OBEM数据。同时, 取得了一系列创新性研究成果: (1)基于人工地震探测及天然地震层析成像结果, 确定南海东北部的地壳属性为受到张裂后期岩浆活动影响的减薄陆壳(12~15km), 划分了南海北部陆缘洋陆边界(Continent-Ocean Boundary, COB); (2)根据多道地震反射剖面, 划分了马尼拉俯冲带北部增生楔前缘的精细结构; (3)圈定了南海停止扩张时洋壳范围; (4)初步构建了南海与菲律宾海板块构造演化模型。本项目为重大研究计划“南海深海过程演变”核心科学问题(海底扩张的年代与过程)提供了实质性的证据, 同时为南海构造演化生命史的“骨架”提供了重要的基础数据, 具有深远的科学意义。 相似文献
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南海北部陆缘洋陆转换带实施的OBS2018-H2测线的地壳速度结构, 将为探讨南海张裂-破裂机制提供重要证据。文章介绍了OBS2018-H2测线前期数据处理流程, 包括多道反射地震数据处理、海底地震仪OBS (Ocean Bottom Seismometer)数据格式转换、炮点和OBS位置校正, 以及OBS震相的初步识别, 并对地壳结构进行了初步分析。结果表明: 炮点和OBS位置校正效果良好; 多道反射地震数据为建立初始速度模型提供了良好约束; OBS综合地震剖面识别了多组清晰的P波震相, 包括Pw、Pg、PmP和Pn震相。根据测线西侧OBS36、OBS37两台站的震相分布特征初步估算台站下方地壳厚度约为6~7km, 与根据多道地震剖面LW3的双程走时估算的厚度6~9km大致相符。 相似文献
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机载激光雷达水深测量是高效获取高精度近岸海底地形的一种新型技术,具有测量精度高、效率高、作业区域广的特点.通过分析CZMIL?Nova?Ⅱ机载激光雷达测深系统获取的南海某岛高分辨率海底地形数据,发现除地貌类型的识别以外,该数据还可用于海底断裂构造的高精度解译.通过对激光雷达测深渲染图像的解译,发现工作区海底地貌由沙嘴、... 相似文献
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为揭示南海南部陆缘的地壳结构, 研究其张裂-破裂机制, 开展共轭陆缘对比, 我们在南沙地块礼乐西海槽附近的洋陆转换带上完成了OBS2019-2测线的探测工作。相较于北部陆缘, 南部陆缘已有的海底地震仪(ocean bottom seismometer, OBS)测线较少, 对深部地壳结构的研究也较少, 因此OBS2019-2测线就尤为重要。文章重点阐述了OBS2019-2测线的数据处理工作, 包括UKOOA文件制作、数据格式转换、位置校正、单个台站综合地震记录剖面的生成等, 然后在剖面图中对各类深部震相(Pg、PcP、PmP、Pn)进行识别追踪, 并建立初步的模型; 使用Rayinvr软件进行走时试算工作, 验证了震相识别的准确性。处理结果显示OBS2019-2测线的深部震相清晰, 最远震相可以连续追踪到120km以外, 数据整体质量良好, 能为后续速度建模和构造解释等工作提供坚实基础。 相似文献
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基于背景噪声互相关技术的海底地震仪的时钟校正方法在西南印度洋脊的应用 总被引：1，自引：0，他引：1
Seismic monitoring using ocean bottom seismometers(OBS) is an efficient method for investigating earthquakes in mid-ocean ridge far away from land. Clock synchronization among the OBSs is difficult without direct communication because electromagnetic signals cannot propagate efficiently in water. Time correction can be estimated through global positioning system(GPS) synchronization if clock drift is linear before and after the deployment. However, some OBSs in the experiments at the southwest Indian ridge(SWIR) on the Chinese DY125-34 cruise had not been re-synchronized from GPS after recovery. So we attempted to estimate clock drift between each station pairs using time symmetry analysis(TSA) based on ambient noise cross-correlation. We tested the feasibility of the TSA method by analyzing daily noise cross-correlation functions(NCFs) that extract from the data of another OBS experiment on the Chinese DY125-40 cruise with known clock drift and the same deployment site. The results suggest that the NCFs' travel time of surface wave between any two stations are symmetrical and have an opposite growing direction with the date. The influence of different band-pass filters,different components and different normalized methods was discussed. The TSA method appeared to be optimal for the hydrophone data within the period band of 2–5 s in dozens of km-scale interstation distances. A significant clock drift of ~2 s was estimated between OBSs sets through linear regression during a 108-d deployment on the Chinese cruise DY125-34. Time correction of the OBS by the ambient noise cross-correlation was demonstrated as a practical approach with the appropriate parameters in case of no GPS re-synchronization. 相似文献
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R. Herber 《Marine Geophysical Researches》1979,4(2):247-253
The ocean bottom seismograph (OBS) of the Institut für Geophysik, Hamburg (IfG) is designed for refraction seismic experiments and for recording microseismic noise. Hydrophone signals are recorded directly on a casette tape recorder with a band width of 3–60 Hz. Signals from three component 1 Hz seismometers are recorded on a 2nd casette tape recorder in FM for a frequency range of 0.1–1 Hz. A telemetering buoy at the surface is connected with the OBS by a polypropylene rope. 相似文献
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借助于国际大洋发现计划平台, 于2017年2月—6月间在南海实施第三次科学钻探(IODP 367-368航次)。海底地震仪(OBS)深地震探测和国际大洋发现计划(IODP)钻探成果相结合, 可以对南海北部洋陆转换带(COT)边界及地质属性的确定提供更好、更全面的深部地质过程解释。文章基于IODP 367-368钻探提出的三种可能设想(下地壳出露、最老洋壳出露、上地幔出露), 分别建立了三种初始速度模型。利用Rayinvr及Tomo2d软件, 对每一种初始模型分别开展了不同OBS间距的射线追踪和走时模拟测试对比, 以及模型的分辨率测试。测试结果表明: OBS间隔为7km比间隔为10km具有更好的射线路径与密度覆盖; 对于上地幔出露模型, 需要足够长的探测测线(>100km), 才能有效得到30km深处信息; 分辨率测试说明, OBS间距需要设置小于或等于7km时, 才能有效分辨20km速度异常体(即模糊带)。 相似文献
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The peculiarities of the microseisms spectra shape when recording on the ocean floor in the frequency band of 0.003–20 Hz are examined. The origin of the stable minima in the microseisms spectrum (“transparency windows”) at frequencies of about 0.02–0.1 Hz and 5–15 Hz is analyzed. In these frequency bands, weak earthquake signals are recorded by bottom instruments. The origin of the low-frequency “transparency windows” can be explained by the conditions of the microseisms propagation in the oceanic waveguide (between the bottom and the water’s surface) in the abyssal plain zones. The results of the full-waveform numerical simulation of the seismoacoustic waves propagation in the oceanic environment and on the ocean-continent border are presented, and the experimental data as well. The peculiarities of the microseisms spectra in the band of high-frequency “transparency windows” can be caused by the constructive resonance in the water-saturated layer of bottom sediments. The theoretical foundation and experimental results are given. 相似文献
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We have reconfigured the Texas digital ocean bottom seismograph (OBS) to operate in a triggered mode and record regional earthquake
signals. This paper reports the results of a deployment program designed to test these digital OBS, by moni toring earthquake
activity in and near the trench in southern Vanuatu (formerly, the New Hebrides). We successfully recorded hundreds of earthquakes,
including 133 located regional earth quakes recorded by three or more stations. We also report J-B residuals for 21 earthquakes
reported and located by the ISC. Fourier analysis of seismograms from regional earthquakes suggest that the frequencies of
spectral peaks at any station were nearly the same for large, small, nearby, and distant events. However, we obtained very
disparate frequencies when we analyzed seismograms for the same earthquake recorded at different stations. The most plausible
interpretation is that spectral peaks do not depend on the characteristics of the earthquake source, but instead on site characteristics,
or, more specifically, on the coupling of the instrument to the seafloor. To record reliable spectral data, we need to overcome
this problem. 相似文献
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With its strong seasonal variation in wave climate and various bathymetric features due to the complex tectonics, the South China Sea (SCS) provides a natural laboratory to study the microseism. We collected data from seismic stations around the SCS and calculated their noise spectra, through which seasonal and spatial variations of microseism, as well as the general feature of seismic ambient noise in this marginal sea were revealed. Microseism seasonal variations in general reflect influences of the East Asian monsoon in winter and the Indian monsoon in summer, respectively. The two microseism components, the single frequency microseism (SFM) and the double frequency microseism (DFM), show striking alternating variation patterns both seasonally and spatially. These variation patterns, along with the bathymetric feature near the stations, indicate SFM and DFM are generated through different physical mechanisms. More interestingly, seasonal and spatial variations of DFM appear to be consistent with the basin-scale surface circulation model of the SCS, in which the upper SCS experiences cyclonic in winter and anti-cyclonic in summer. These consistencies provide observational evidence for the hypothesis that the cyclonic depression is a favorable condition to generate DFM. 相似文献
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Jonathan D. Tuthill Brian T. R. Lewis Jan D. Garmany 《Marine Geophysical Researches》1981,5(1):95-108
The Lopez Island OBS Intercomparison Experiment provided a data set of sufficient spatial density to allow study of the propagation of shot-generated Stoneley waves as well as ambient background noise. The Stoneley waves were observed propagating at velocities of 20 to 50 m s-1, Phase velocities were determined by fitting peaks in the frequency wave number spectrum. Group velocities were calculated by narrowly filtering the data and determining the arrival time of the peak in the frequency packet. Particle displacement plots illustrate the surface wave character of these waves. The analysis of the ambient background noise failed to produce a clearly defined dispersion curve yet it did allow bounds to be placed on the phase velocities (20 to 50 m s-1). The data were modeled using eleven layers overlying a half-space. The results indicated that the top 7 m of the sediment column at Lopez Island is best approximated by two zones. In the upper zone there is a fairly rapid change of shear velocity with depth. This zone overlies a region in which the shear velocity gradient is much lower. Deep ocean background noise recorded by University of Washington ocean bottom seismometers was also examined. Although insufficient data precluded any velocity analysis, definite similarities exist between these data and noise data observed at Lopez Island.Hawaii Institute of Geophysics Contribution No. 1174. 相似文献
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天然气水合物是一种新型的清洁能源, 南海北部神狐海域的地质条件有利于水合物的形成和储藏。传统的多道地震(MCS)数据难以得到精确的速度信息, 并且只能从时间域上判断地质体纵向分布。海底地震仪(OBS)是一种常用的主动源地震仪器, 可以接收到更清晰的气枪信号。相比于MCS, OBS剖面上的折射震相可以揭示较深部的地层速度信息。文章结合MCS和OBS的优势, 识别水平叠加剖面上的反射层位, 并得到初始模型; 将OBS剖面和水平叠加剖面拼合, 从而判断OBS剖面上反射震相所对应层位; 拾取OBS台站上的反射和折射震相, 使用RayInvr软件正演模拟得到水合物存在区域的二维速度模型, 解决了MCS中较为困难的时深转换问题。最终模型显示了水合物、游离气区域的埋深、厚度和速度, 以及似海底反射(BSR)下方更深部界面的深度和速度特征。 相似文献