| LIU Yunlong,LIU Cai,TAO Chunhui,YAO Huajian,QIU Lei,WANG Ao,RUAN Aiguo,WANG Hanchuang,ZHOU Jianping,LI Huaiming,DONG Chuanwan. 2018. Time correction of the ocean bottom seismometers deployed at the southwest Indian ridge using ambient noise cross-correlation. Acta Oceanologica Sinica, 37(5):39－46 |
| Time correction of the ocean bottom seismometers deployed at the southwest Indian ridge using ambient noise cross-correlation |
| 基于背景噪声互相关技术的海底地震仪的时钟校正方法在西南印度洋脊的应用 |
| Received:September 07, 2017 Revised:January 03, 2018 |
| DOI：10.1007/s13131-018-1209-1 |
| Key words:clock drift cross-correlation ambient noise OBS |
| 中文关键词: 钟漂 互相关 背景噪声 海底地震仪 |
| 基金项目:China Ocean Mineral Resources R & D Association Major Project under contract No. DY135-S1-01; the National Natural Science Foundation of China under contract Nos 41506078, 41706042 and 41522404; the Basic Research Foundation of Second Institute of Oceanography, SOA under contract No. JG0608. |
| Author Name | Affiliation | E-mail | | LIU Yunlong | College of Geoexploration Science and Technology, Jilin University, Changchun 130026, China
Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China | | | LIU Cai | College of Geoexploration Science and Technology, Jilin University, Changchun 130026, China | | | TAO Chunhui | College of Geoexploration Science and Technology, Jilin University, Changchun 130026, China
Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China | taochunhuimail@163.com | | YAO Huajian | Laboratory of Seismology and Physics of Earth's Interior, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China | | | QIU Lei | Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China | | | WANG Ao | Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China
Institute of Geophysics and Geomatics, China University of Geosciences, Wuhan 430074, China | | | RUAN Aiguo | Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China | | | WANG Hanchuang | Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China | | | ZHOU Jianping | Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China | | | LI Huaiming | Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China | | | DONG Chuanwan | Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China
School of Earth Sciences, Zhejiang University, Hangzhou 310027, China | |
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| Abstract: |
| Seismic monitoring using ocean bottom seismometers (OBS) is an efficient method for investigating earthquakes in mid-ocean ridge far away from land. Clock synchronization among the OBSs is difficult without direct communication because electromagnetic signals cannot propagate efficiently in water. Time correction can be estimated through global positioning system (GPS) synchronization if clock drift is linear before and after the deployment. However, some OBSs in the experiments at the southwest Indian ridge (SWIR) on the Chinese DY125-34 cruise had not been re-synchronized from GPS after recovery. So we attempted to estimate clock drift between each station pairs using time symmetry analysis (TSA) based on ambient noise cross-correlation. We tested the feasibility of the TSA method by analyzing daily noise cross-correlation functions (NCFs) that extract from the data of another OBS experiment on the Chinese DY125-40 cruise with known clock drift and the same deployment site. The results suggest that the NCFs' travel time of surface wave between any two stations are symmetrical and have an opposite growing direction with the date. The influence of different band-pass filters, different components and different normalized methods was discussed. The TSA method appeared to be optimal for the hydrophone data within the period band of 2-5 s in dozens of km-scale interstation distances. A significant clock drift of~2 s was estimated between OBSs sets through linear regression during a 108-d deployment on the Chinese cruise DY125-34. Time correction of the OBS by the ambient noise cross-correlation was demonstrated as a practical approach with the appropriate parameters in case of no GPS re-synchronization. |
| 中文摘要: |
| 利用海底地震仪进行地震监测是调查远离大陆的洋中脊地震非常有效的手段。由于电磁波信号不能在水中传播，海底地震仪之间的时间同步非常困难。假设时钟漂移是线性的，那么其校正可以通过海底地震仪投放前后与GPS对时的方式来完成。然而，中国大洋34航次在西南印度洋脊布放的部分海底地震仪回收后，由于仪器故障不能与GPS进行对钟。因此，我们采用一种基于背景噪声互相关技术的时间对称性分析方法来估计台站间的时钟误差。首先利用钟漂已知的中国大洋40航次海底地震数据的每天噪声互相关函数来测试时间对称性分析方法的可行性，结果表明任意两个台站的面波互相关函数的走时随时间向着相反的方向发展；其次讨论了不同的地震数据分量，频带范围，振幅归一化方法等参数对互相关结果的影响，我们发现时间对称分析方法在经过2-5 s滤波后的水听器分量数据中应用效果最佳。最后将该方法应用到中国大洋34航次108天地震监测数据中，得到海底地震台站之间累积的最大钟漂约为2 s。根据实际应用的效果，我们证实了在没有GPS授时情况下选择合适的参数利用背景噪声互相关方法是的一种切实可行的时钟校正方法。 |
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