国产I-4C型OBS在西南印度洋中脊的试验   总被引：10，自引：4，他引：6       下载免费PDF全文

阮爱国  李家彪  陈永顺  丘学林  吴振利  赵明辉  牛雄伟  王春龙  王显光 《地球物理学报》2010,53(4):1015-1018

介绍了在DY115-21航次第6航段西南印度洋中脊构造调查中,中国科学院地质与地球物理研究所研制的5台I-4C型海底地震仪（OBS）的试验情况.在不同的水深点（2370～3534 m）共投放OBS 6个台次,全部投放和回收成功.OBS内置电化学式和外置机械式两种上浮释放系统都成功动作,取得了船载气枪震源的地震数据.但仍存在三个主要问题：第一,上浮后的GPS应答搜寻系统无效果;第二,夜间回收时所需的灯光明亮度较差;第三,外在结构不利于海面上的姿态控制和打捞.  相似文献   

Observation of shear‐wave splitting in the multicomponent node data from Atlantis field,Gulf of Mexico     

Samik Sil  Ravi P. Srivastava  Mrinal K. Sen 《Geophysical Prospecting》2010,58(6):953-964

In 2005, a multicomponent ocean bottom node data set was collected by BP and BHP Billiton in the Atlantis field in the Gulf of Mexico. Our results are based on data from a few sparse nodes with millions of shots that were analysed as common receiver azimuthal gathers. A first‐order look at P‐wave arrivals on a common receiver gather at a constant offset reveals variation of P‐wave arrival time as a function of azimuth indicating the presence of azimuthal anisotropy at the top few layers. This prompted us to investigate shear arrivals on the horizontal component data. After preliminary processing, including a static correction, the data were optimally rotated to radial (R) and transverse (T) components. The R component shows azimuthal variation of traveltime indicating variation of velocity with azimuth; the corresponding T component shows azimuthal variation of amplitude and phase (polarity reversal). The observed shear‐wave (S‐wave) splitting, previously observed azimuthal P‐wave velocity variation and azimuthal P‐wave amplitude variation, all indicate the occurrence of anisotropy in the shallow (just below the seafloor) subsea sediment in the area. From the radial component azimuthal gather, we analysed the PP‐ and PS‐wave amplitude variation for the first few layers and determined corresponding anisotropy parameter and V_P/V_S values. Since fracture at this depth is not likely to occur, we attribute the observed azimuthal anisotropy to the presence of microcracks and grain boundary orientation due to stress. The evidence of anisotropy is ubiquitous in this data set and thus it argues strongly in favour of considering anisotropy in depth imaging for obtaining realistic subsurface images, at the least.  相似文献   

Formulation of the linearized forward problems for multicomponent OBS data in a water/solid configuration using the reciprocity theorem     

Luc T. Ikelle  & Lasse Amundsen 《Geophysical Journal International》2000,141(2):527-534

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南海IODP 367-368钻探区深地震探测的OBS站位设计分析     

王强  赵明辉  张佳政  孙龙涛  丘学林 《热带海洋学报》2018,37(1):90-97

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   

SAN-OBS存储网络体系的设计及其联接层的实现     

王玲 《成都信息工程学院学报》2006,21(3):344-349

存储体系结构的设计是网络存储技术发展中的一个关键.阐述了将SAN（Storage Area Network）体系结构和OBS（Object-Based Storage）体系结构的联接,构成一个新的综合存储体系SAN-OBS.以实现一个易于异构平台共享,易于管理和实现,有高性能和高安全性的存储网络体系.主要包括SAN-OBS的结构模型、功能分布、联接层实现等内容.  相似文献   

声学光学法泥沙浓度观测的对比研究          下载免费PDF全文

胡捷  徐继尚  牛建伟  董平  秦宽宽 《海岸工程》2016,35(1):47-57

根据光学后散射传感器(Optical Backscatter Sensor,OBS)和声学后散射传感器(Acoustic Backscatting Sensor,ABS)估算悬浮沉积物质量浓度(Suspended sediment concentration,SSC)的原理,在水槽实验室不同波况产生较高悬浮沉积物质量浓度的条件下运用OBS仪器ASM-IV(激光边界层泥沙剖面仪)和ABS仪器AQUAscat1000(多频声学悬沙剖面仪)观测并记录数据。然后用水槽实验抽取的水样标定光学和声学仪器,反演得到高精度的垂向泥沙浓度分布剖面。结果表明,OBS仪器ASM-IV上的不同光学探头测得的浊度与SSC可以用同一个线性关系描述,相关系数高达0.996,进而能够高精度(垂向间距1cm)地反演垂向的SSC剖面;对于本组水槽实验的粉土底质和不同的波况而言,声学仪器比光学仪器的量测精度低;不同频率声学仪器换能器的量测值可相差几个数量级,不同波况条件下的声学仪器反演值与实测SSC的相关性系数在0.716~0.974变化。  相似文献   

OBS海洋环境信号分析与应用     

童思友  廖仪  陈亮  吴志强 《海洋科学》2016,40(2):145-150

为研究海洋环境信号在OBS(Ocean Bottom Seismograph)原始数据中的规律及应用,根据OBS原始数据的波形及频谱特征,将研究区划分为5个时间段,依次为旧涌浪阶段、风浪渐强阶段、风浪全盛阶段、风浪消退阶段和新涌浪阶段。结合海洋天气预报,认为上述现象是由偏南风风浪对海流的影响造成的。参考野外地震数据采集记录班报,得到各阶段的时长和距离,计算风浪渐强、全盛和消退阶段OBS附近海流的平均速度。结果表明:OBS原始资料中浅海海洋环境噪音增强的主要因素是风浪,且风浪引起的噪音信号的波形变化特征是渐进式的;OBS可用于接收某种特殊阶段(如台风、海啸等)的噪音信号,并根据噪音信号的波形特征、频谱变化规律和持续时间估算该阶段的海流速度变化。  相似文献   

Combination of Least Square and Monte Carlo Methods for OBS Relocation in 3D Seismic Survey Near Bashi Channel     

Feng Du  Fudong Yang  Minghui Zhao  Qiang Wang  Xuelin Qiu 《Marine Geodesy》2013,36(5):494-515

Abstract

The relocation of ocean bottom seismometers (OBSs) is a key step in analyzing the three-dimensional seismic tomographic structure of crust and mantle. In order to get the accurate location of OBSs on the seafloor, we analyze the travel times of direct water waves emitted by air-guns. The Monte Carlo and least square methods have been adopted to calculate the true OBS location. The secondary time correction is necessary if the arrivals of direct water waves show overall time drift during relocation which maybe originates from remnant of linear clock drift correction and average errors of travel time picking, mean water velocity assumption, and experiment geometry. We have improved the original OBS relocation procedure which we used previously for other experiments by deliberateness of a secondary time correction and automatically approaching the really mean water velocity. A series of synthetic tests are carried out firstly to document the feasibility of our procedure and then it is applied on a real experiment. In here, we relocate 28 OBSs in total were relocated in 3D seismic survey near Bashi Channel. Relocation results show that the drifting distances for the 28 OBSs range from 65 to 1136 m between the deployed and relocated locations deduced by relocation results. The Pearson correlation coefficient between OBS drifting direction and sea current direction is 0.79, indicating that the two sets of data are highly linearly related and further manifest the sea current as the most possible driving force for OBS drifting during landing on the seafloor but its detailed influence mechanism is unclear by now. This research is necessary and critical for velocity structure modeling, and the optimal relocation program provides valuable experiences for 3D seismic survey in other area.  相似文献   

OCEAN BOTTOM SEISMOMETER AND ONSHOREOFFSHORE SEISMIC EXPERIMENT IN NORTHEASTERN SOUTH CHINA SEA   总被引：7，自引：0，他引：7  

QIU Xuelin~ 《大地构造与成矿学(英文版)》2004,28(1):28-35

Three-component Ocean Bottom Seismometers, portable land stations and marine air gun seismic sources were used to carry out an onshore-offshore deep seismic profile in northeastern South China Sea. This profile, orientated in NNW-SSE, was as long as 500 km and perpendicular to the strike of regional tectonics. The offshore data were processed in Taiwan Ocean University using a number of available software and the onshore data were analyzed in South China Sea Institute of Oceanology by new-written programs and public software. Preliminary results show that the seismic data are in good quality and contain rich information of deep structure. Seismic phases, e.g. Pg, PmP and Pn, are identified in the offset range 5～220 km, which will provide an important dataset for the deep crustal structure and oil-gas basin evolution studies of this region.  相似文献   

Seismological structure and implications of collision between the Ontong Java Plateau and Solomon Island Arc from ocean bottom seismometer–airgun data     

Seiichi Miura  Kiyoshi Suyehiro  Masanao Shinohara  Narumi Takahashi  Eiichiro Araki  Asahiko Taira   《Tectonophysics》2004,389(3-4):191

A seismic refraction–reflection experiment using ocean bottom seismometers and a tuned airgun array was conducted around the Solomon Island Arc to investigate the fate of an oceanic plateau adjacent to a subduction zone. Here, the Ontong Java Plateau is converging from north with the Solomon Island Arc as part of the Pacific Plate. According to our two-dimensional P-wave velocity structure modeling, the thickness of the Ontong Java Plateau is about 33 km including a thick (15 km) high-velocity layer (7.2 km/s). The thick crust of the Ontong Java Plateau still persists below the Malaita Accreted Province. We interpreted that the shallow part of the Ontong Java Plateau is accreted in front of the Solomon Island Arc as the Malaita Accreted Province and the North Solomon Trench are not a subduction zone but a deformation front of accreted materials. The subduction of the India–Australia Plate from the south at the San Cristobal Trench is confirmed to a depth of about 20 km below sea level. Seismicity around our survey area shows shallow (about 50 km) hypocenters from the San Cristobal Trench and deep (about 200 km) hypocenters from the other side of the Solomon Island Arc. No earthquakes occurred around the North Solomon Trench. The deep seismicity and our velocity model suggest that the lower part of the Ontong Java Plateau is subducting. After the oceanic plateau closes in on the arc, the upper part of the oceanic plateau is accreted with the arc and the lower part is subducted below the arc. The estimation of crustal bulk composition from the velocity model indicates that the upper portion and the total of the Solomon Island Arc are SiO₂ 58% and 53%, respectively, which is almost same as that of the Izu–Bonin Arc. This means that the Solomon Island Arc can be a contributor to growing continental crust. The bulk composition of the Ontong Java Plateau is SiO₂ 49–50%, which is meaningfully lower than those of continents. The accreted province in front of the arc is growing with the convergence of the two plates, and this accretion of the upper part of the oceanic plateau may be another process of crustal growth, although the proportion of such contribution is not clear.  相似文献