分体式宽频带海底地震仪的研制、测试和数据质量分析

Seismometer-detached broadband ocean bottom seismograph(OBS):development,test,and data quality analysis

宽频带海底地震仪(OBS)是进行海洋岩石圈结构成像等地震学基础研究的核心仪器设备.本文介绍了南方科技大学自行研制的分体式宽频带OBS(命名为磐鲲)的设计特点及其在南海深海区的测试状况;并对于设备性能和数据质量进行了细致分析.除了分体式结构以外,磐鲲还具有独特的抗底流设计、地震计自动分离装置、宽频带地震计(100 Hz~120 s)、以及低功耗和长工作时间等特点.与2012年在南海进行的地震观测实验中的OBS设备相比,磐鲲在回收率、水平方位确定、调平装置以及时钟精度等OBS设备的基本性能方面都有了明显的提高;更为重要的是,得益于独特的抗底流结构,磐鲲记录的地震波形质量有了较大改善,尤其是水平分量,达到了与附近陆地台站相近的数据质量,而低频成分(>10 s)的噪声水平低于国际同类OBS.这些分析说明磐鲲记录的数据可以实现绝大多数地震学研究目标,包括应用于接收函数和各向异性等需要使用三分量地震数据的常用方法.此外,其数据的宽频带特征,尤其是较高质量的低频信号(如长周期面波的频散特征和低频体波的有限频效应),将更有利于研究海洋岩石圈和上地幔的深部结构和过程.

The broadband ocean bottom seismograph(OBS)is the core instrument for seismological studies such as imaging the oceanic lithosphere.This paper presents the design of the domestic seismometer-detached broadband OBS(Pankun)and its tests in the South China Sea(SCS),as well as a detailed analysis of its performance and data quality.In addition to the seismometer-detached type,Pankun has the following features:a unique anti-current structure,an automatic device separating the seismometer,a broadband seismometer(100 Hz~120 s),and low-power consumption and long operational time.Compared with the OBSs in the previous experiment in 2012,Pankun has much better performances in recovery rate,horizontal orientation determination,leveling device,and clock accuracy.More importantly,the quality of earthquake waveforms has also been greatly improved benefits from its unique anti-current structure,especially for the horizontal components.The quality of horizontal components of Pankun is comparable to nearby land stations,while low-frequency components(>10 s)have lower noise levels than international counterparts.These analyses show that Pankun′s data can be used for most seismological applications,including receiver function and anisotropy analysis that require three-component seismic data.Finally,the broadband characteristics of Pankun′s data,especially high-quality,low-frequency signals,are more conducive to studying the structure and processes of the oceanic lithosphere and upper mantle using the long-period surface waves and the finite frequency body waves.