基于初至波拟合地震采集同步方法研究

Research on a Quantitative Determination Method of Seismic Aquisition Synchronization Based on First Break Fitting

海底电缆地震采集中震源和仪器记录的同步对地震资料采集起到至关重要的作用,空气枪震源系统与仪器记录系统在不同的船舶,分别具有独立的GPS授时时间(UTC时间)系统,综合导航系统以GPS授时时间为准下达同步指令。由于GPS授时监测技术不完善,当GPS授时系统出现异常时不能及时发现,会导致震源激发与仪器记录不同步,表现在地震资料记录不完整,初至波到达时间不一致。通过对初至波的分析和探讨,提出了利用初至波拟合在海底电缆地震采集作业现场定量检测地震采集同步的方法,通过在渤海某工区实际应用,通过该方法发现地震采集不同步现象,并判断出由于仪器船GPS授时不准造成了不同步,保证了后续地震采集资料可靠性。

The synchronization of seismic source and instrument records in submarine cable seismic acquisition plays an important role in seismic data acquisition.The air-gun source system and recording system have independent GPS timing time(UTC)systems in different vessels,and the integrated navigation system issues synchronization instructions based on GPS timing time.Due to the imperfection of GPS timing monitoring technology,when there is an abnormality in the GPS timing system,it cannot be found in time,which will result in the source excitation and instrument record being out of sync,which is manifested in the incompleteness of seismic record and the inconsistency of arrival time of the firstbreak.This paper proposes a method of the seismic acquisition synchronization in the process of detection on the submarine cable assignments by using first break fitting through the analysis and discussion of primary wave,and its practical application to a project in the Bohai bay.Through this method,the asynchronous phenomenon ofseismic acquisition has been found,and it also determines that the phenomenon results in the incorrect instrumentation vessel GPS timing,ensuring the reliability of seismic acquisition data.