基于背景噪声互相关技术的雅浦俯冲带海底地震仪时间校正

由于电磁波无法在水中传播,导致海底地震仪(OBS)与全球定位系统(GPS)无法进行实时对钟,因此会产生一定的时钟漂移.而受船时、海况等影响,被动源OBS在回收后往往电量亏损,致使设备回收时并没有完成对钟,无法直接利用对钟前后的时钟漂移量进行线性校正.本文选取中国科学院海洋研究所2016—2017年间在雅浦俯冲带进行的长周期被动源OBS实验所获得的数据,利用背景噪声互相关方法对OBS进行了时间校正.结果发现,各OBS在经过一年左右时间的布放后,时钟漂移量在1～3 s之间,且基本呈线性趋势,将该结果平均分配到每天从而完成线性校正.另外,探讨了时钟的非线性漂移、误差源、参考台站的选取等因素对时钟准确度的影响,为OBS的数据处理进行了有益的探索.

Time correction of Ocean Bottom Seismometer(OBS) deployed at the Yap subduction zone using ambient noise cross-correlation

Clock synchronization cannot be finished in real-time between Ocean Bottom Seismometer(OBS)and the Global Positioning System, due to the block of seawater to the propagation of the electromagnetic wave. Thus, the clock drifting will occur during the deployment of OBS in the seawater. Meanwhile, limited by other factors, such as the ship’s schedule, and conditions of the sea, clock synchronization could not be finished due to power exhaustion of the recovered passive OBS. As a result, the general linear time correction can’t be implemented. From 2016 to 2017, an array of passive OBSs was deployed on both sides of the Yap Trench for long-term observation with the research vessel Kexue from the Institute of Oceanology, Chinese Academy of Sciences. In this study, time correction is conducted based on the data obtained by these OBSs and the ambient noise cross-correlation functions. The results show that the clock drifting of each OBS ranges from 1 to 3 second after one-year deployment and changes roughly linearly. The linear time correction of each OBS is finished by distributing the above result equally to every day. In addition, the influence of the nonlinear drifting of the clock, the error source and the selection of the referential station on the clock accuracy are discussed, which would be beneficial to the OBS data processing.