国产海底地震仪的时间记录与原始数据精细校正

海底地震仪(OBS)的时间记录对数据处理是至关重要的.实践发现,部分国产便携式OBS的数据记录存在较大的内部时间误差,并且实测地震剖面异常的同相轴"断阶"、"倾斜"现象时有发生.我们通过自激自收试验,对这些异常现象进行了验证,确认其来源于OBS数据文件内部时间漂移,以及数据处理程序存在的缺陷.统计表明,A、B型OBS内部时间漂移量在250Hz的预设采样率下为0～40ms,L、S型OBS在100Hz下为0～90ms.这个量级的时间漂移,会对OBS数据处理、计算模拟产生影响.进一步,我们采用计算实际采样间隔、调整采样间隔、数据重采样的方法,对这种误差进行校正,并且改进了相关的OBS数据处理程序.本文的研究加深了对OBS数据时间记录误差的认识,得到了OBS数据文件内部时间漂移的分布规律,使得中等及较大程度的内部时间漂移的精细校正得到重视,进而完善了OBS数据处理步骤和流程,对OBS数据的有效利用进行了重要补充,为国产OBS的广泛使用、仪器研发提供了重要参考.

Time record and accurate correction of Chinese OBS raw data

Time record of the Ocean Bottom Seismometer (OBS) is crucial for data processing. Larger internal time drift errors were discovered in some Chinese portable OBSs, which result in "stair" or "incline" events on observed seismic record sections. We designed zero-offset experiments to verify these abnormal phenomena, confirming that they are caused by internal time drift of data files as well as some bugs existing in data processing programs. According to the statistics, internal file time drift of A or B-type OBS at the preset sampling rate of 250 Hz is between 0 and 40 ms, while this drift of L or S-type at 100 Hz is between 0 and 90 ms, which can affect OBS data processing and structural simulation. We corrected this time error by means of actual sampling interval calculation, sampling interval adjustment and data re-sampling. Some modifications were also made to relevant OBS data processing programs. Our research promotes the awareness of time records of OBS data, acquires the regularity of internal file time drift variation, and highlights the accurate correction of the intermediate and larger extent of this time error. Our work improves the OBS data processing steps and flow chart, makes a significant supplement for effective utilization of OBS data, and provides an important reference for extensive use and development of domestic OBSs.