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为了调查南海北部陆坡的天然气水合物的分布及其速度特征,广州海洋地质调查局在该海域进行了一系列的四分量(4-Component,简称4C)海底高频地震仪(Ocean Bottom Seismometer,简称OBS)测量。本文对该局在该海域采集的四分量OBS站点地震数据进行成像处理。处理的关键步骤包括重定位、重定向、水陆检合并、镜像偏移。站点的重定位与重定向是使得四分量数据正确归位。水陆检合并是指水检和陆检的匹配,相加和相减分离上行波和下行波。上行波用于常规成像,下行波可用于镜像偏移。由于节点稀疏,上行波的常规成像无法识别天然气水合物分布。镜像偏移是利用检波点的下行波进行成像,既改善浅地层的构造照明,又提高了天然气水合物矿体的成像精度,可建立精确的速度模型。通过下行波成像,镜像偏移剖面构造特征清晰,分辨率高,海底、天然气水合物地震识别标志-似海底反射(Bottom Simulating Reflection,简称BSR)与高分辨率剖面和速度特征相吻合。
In order to investigate the distribution and velocity characteristics of gas hydrate on the northern slope of the South China Sea, the Guangzhou Marine Geological Survey carried out a series of 4-Component (4C) Ocean Bottom Seismometer OBS) measurement. In this paper, the seismic data of the four-component OBS site acquired by the Bureau in this area are processed. The key steps in processing include relocation, redirection, aquatic consolidation, and image migration. Site relocation and redirection is to make the four-component data correctly homing. Water and land inspection merge refers to the water and land inspection match, add and subtract the separation of upstream and downstream waves. Upstream waves are used for normal imaging, and down waves can be used for mirror offsets. Due to the sparse nodes, conventional imaging of upwelling waves does not recognize the gas hydrate distribution. Image offset is the use of wave detection point of the downlink imaging, not only to improve the illumination of shallow formations, but also improve the imaging accuracy of gas hydrate ore body, you can establish an accurate velocity model. Through the down-wave imaging, the structure of the image-offset section is characterized by a clear structure and high resolution. Bottom Simulating Reflection (BSR), a seismic signature of the seabed and gas hydrate, is consistent with the high-resolution profile and velocity characteristics.