岛礁地震资料特征分析及处理流程——以西沙永乐环礁为例

岛礁为国际科学研究前沿，其内部结构是揭示深海地质演变、古环境古气候变化等科学问题和解决岛礁建设、人造岛礁等工程问题的关键。西沙永乐环礁历经南海地质演变过程，发育了世界最深海洋蓝洞，为我国岛礁研究重点区域，但受限于探测手段和成像方法目前尚未窥得其内部结构。以西沙永乐环礁为例，利用3.125m道间距高分辨地震探测试验数据，开展岛礁地震资料特征分析，探索岛礁地震资料处理流程和岛礁地震处理方法，提升岛礁地震资料信噪比、分辨率和成像准确度，获取反映岛礁内部结构的高精度地震成像剖面。研究结果表明：本文提出的岛礁地震资料处理流程在海底珊瑚礁绕射波偏移归位、岛礁内部浅层结构和深水盆地区域地震同相轴刻画方面具有优势，将为我国下一步的南海岛礁地震资料采集和处理提供借鉴。

Characteristics of seismic data and its processing procedures in the areas of Reef Islands——a case from Yon-gle Atoll of Xisha Islands

Reef islands have recently become one of the hot interests in international geoscientific researches. Recent progress indicates that the internal structure of reef island is the key to some scientific issues, such as deep-sea geological evolution, paleo-environmental and paleo-climatic changes and to some engineering problems, for example, the construction of man-made reefs and islands. The Yongle Atoll in the Xisha Islands of the South China Sea, which has experienced the geological evolution as part of the South China Sea and become famous because of the deepest Blue Hole in the world, is a key area for marine scientific research in China. However, the internal structure of the islands is not clear at present due to lack of detecting facilities and imaging methods. Based on the collected high- resolution seismic data with 3.125m trace distance from the Yongle Atoll, this paper revealed for the first time the fine internal structure of the reef islands of the Yongle Atoll with high-precision seismic images by enhancing the signal-to-noise ratio, resolution and imaging accuracy of the seismic data via improvement of seismic data analysis, seismic data processing process and seismic imaging methods. The output indicates that the seismic data processing procedures promoted by this paper has advantages in the migration and reorientation of the seabed reef's diffraction wave, working out clearer shallow structures inside the reef, and acquiring the in-phase axis of seismic reflection from deep water. Our study proves that it is a suitable and effective method for seismic data acquisition and processing in the area of reef islands as such in the South China Sea of China.