海底地震仪的信号传递效果和噪声水平  

Signal transfer and noise level of Ocean Bottom Seismometers

作　　者：王笋[1,2,3] 丘学林 赵明辉[2,3] 李普春 刘丽华[5] 张艺峰 谢志招[1] WANG Sun;QIU XueLin;ZHAO MingHui;LI PuChun;LIU LiHua;ZHANG YiFeng;XIE ZhiZhao(Xiamen Centre for Seismic Survey,Fujian Earthquake Agency,Xiamen Fujian 361021,China;Key Laboratory of Ocean and Marginal Sea Geology,South China Sea Institute of Oceanology,Chinese Academy of Sciences,Guangzhou 510301,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;Guangdong Earthquake Agency,Guangzhou 510070,China;Key Laboratory of Petroleum Resource Research,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China)

机构地区：[1]福建省地震局厦门地震勘测研究中心,福建厦门361021 [2]中国科学院南海海洋研究所,边缘海与大洋地质重点实验室,广州510301 [3]中国科学院大学地球与行星科学学院,北京100049 [4]广东省地震局,广州510070 [5]中国科学院地质与地球物理研究所,油气资源研究重点实验室,北京100029

出　　处：《地球物理学报》2019年第8期3199-3207,共9页Chinese Journal of Geophysics

基　　金：国家自然科学基金(U1505232,41674092,41649908,91428204,91858212);福建省地震局青年科技基金(Y201707)联合资助

摘　　要：单球式海底地震仪(以下简称OBS)由于其成本低、操作简便的优点在天然地震研究、人工地震探测中获得了广泛应用.本文首先分析多型进口和国产OBS在台湾海峡西部采集的地震数据,发现同一台OBS上的垂直向速度检波器(Z分量)的信噪比常显著低于压力检波器(H分量),由于这两种检波器记录的都是海底的垂向振动信号,推测速度检波器的低信噪比更多的与仪器特性有关.然后从信号传递和噪声水平两方面分析影响速度检波器信噪比的因素:为检测速度检波器与OBS壳体的耦合效果,对某型宽频带OBS和陆上地震仪进行了同址同步观测试验,发现OBS的整机灵敏度有较大的差异;为分析速度检波器的水底噪声特征,以H分量记录作为基准,对比分析了同一台仪器不同站位的Z分量噪声水平,发现速度检波器在浅海区受到较大的次生干扰.本文指出OBS的内部耦合和水流次生干扰是至今尚未引起大家重视而又严重影响资料品质和多波探测成效的两个关键问题,这一研究结果对于改进OBS结构设计和制造工艺,以及OBS数据多分量处理方法研究有重要的参考意义.Due to the features of low cost,small volume and easy to operate,single-sphere type OBSs are widely used in active and passive seismic observation.We check the OBS data in West Taiwan Strait and conclude that:Signal to Noise Ratio(SNR)of the hydrophone(H-component)usually greater than that of the vertical component geophone(Z-component)of the same OBS.Because the two types of detectors are designed to monitor the vertical movement of the seabed,we suggest that the significant difference between the two SNRs is related to the instrument characteristics.This paper makes analysis on the low SNR of Z-component by two ways:the signal transfer and the noise level.To determine the coupling of geophones and shell,we measure and analyze the seismograms of three broadband OBS in the same batch,together with two broadband land seismographs(CMG40-TDE)as a frame of reference.Our results show that there exist large variations of the internal damper not only between the OBSs,but also between the three components of the same OBS.Attempting to discern the cause of the noise levels,we analyze the noises recorded by the same OBS in 7 different sites.The results show that the geophones are sensitive to the secondary disturbances in shallow water zone.We pinpoint that the internal coupling and the secondary water disturbances significantly affect the data quality of OBS and the outcome of multi-component exploration,which did not get deserved concern before.This study proposes an important developing direction for the architecture design and manufacturing technology of OBS,and provides a good reference for the multi-component seismic processing of OBS data.

关 键 词：海底地震仪 信噪比 信号传递效果 噪声水平 

分 类 号：P738[天文地球—海洋地质]