西南印度洋洋中脊热液A区海底地震仪数据处理初步成果

OBS seismic data processing and preliminary results on the hydrothermal field of the Southwest Indian Ridge

在西南印度洋热液活动A区(49°39′E)开展的三维海底地震仪(OBS)探测实验为研究该区域的深部地壳/上地幔结构提供了重要基础,而OBS数据处理是获取研究区三维速度结构的基础环节。文章介绍了此次实验中所用的3种不同类型OBS(国产、法国和德国OBS)的数据处理流程,包括地震数据解编处理、截裁处理和地震信号的可视化处理;并以第2790炮为例分析了3种类型OBS记录数据的波形和频谱特征。结果表明,由于受不同类型OBS的频带、传感器和拾震器等影响,国产与法国OBS都能记录到长周期和短周期噪音,而德国OBS只记录到短周期噪音;但经带通滤波后,3种类型OBS都能够很好地压制噪音,突出有用的气枪信号;对比3种类型OBS(分别以OBS04、OBS08和OBS23为例)沿主测线X1X2的综合记录剖面,发现3种类型OBS都能够记录到多组清晰可靠的P波震相,如直达水波、Pg、PmP和Pn震相,为下一步A区的三维层析成像奠定了坚实数据基础。

Three-dimensional（3D） ocean bottom seismometer（OBS） survey provides a significant foundation for the deep crustal and upper mantle structure of the hydrothermal field（49°39′E）（Area A） in the Southwest Indian Ridge.OBS data processing is the basic step of obtaining the 3D seismic velocity structure.The flow steps for data processing of three types of OBS（domestic,French and Germanic OBS） were firstly introduced,containing the decompilation,cutting and seismic signal visualization.Taking the shot 2790th for example,waveforms and frequency spectrums of three types of OBSs were then analyzed,which were related to frequency band,sensor and seismograph for different OBSs.Domestic and French OBSs recorded long-periodic and short-periodic noises,and Germanic OBS only recorded short-periodic noises.However,air-gun signals were highlighted and noises were suppressed for all the OBSs after using a band-passed filter.Moreover,several seismic phases,e.g.,Pg,PmP and Pn,were clearly revealed in the recorded seismic sections of three types of OBSs（OBS04, OBS08 and OBS23） along the profile X1X2.These phases will provide a strong data base for 3D tomography for studying Area A.