在井下地震观测中，各种地表背景噪声具有显著衰减作用，针对中国地震科学台阵现有大量非专用浅井式设计的Guralp CMG系列地震计，以及目前多个新获批项目在高背景噪声区域的观测需求，设计一种野外实用浅井观测方式，在北京国家地球观象台进行不同深度、不同井壁材质的观测对比实验，分析研究观测数据的背景噪声功率谱密度，结果表明，随着浅井深度的增加，地震背景噪声在垂直、水平向得到改善，改善程度随频率变化有所不同。分析认为，在华北现有地质环境下，6 m浅井是较为经济的观测方式，性价比高、占地小、施工简便，可用于后续多个项目的宽频带流动地震台阵观测。
The borehole installation used in broadband seismic observations shows significant attenuations for several types of background seismic noises, however, it can hardly be directly employed in a large-scale portable seismic array due to its relatively high cost. Recently developed posthole seismometers offered the obvious improvement of noise performance with a reasonable cost in installation, and might present a new trend of future broadband seismic observation. Considering the facts that many portable broadband seismic stations will be deployed at regions with high background seismic noise and the mainly used sensors are Guralp-CMG Series seismometers which, however, are not specially posthole designed, this paper demonstrated a special installation method for non-posthole designed seismometers such as Guralp-CMG series, experimented at Beijing National Earth Observatory, and studied the corresponding noise performances. The results show that the noise decreases are found for both vertical and horizontal components, and varied with the frequencies, the biggest improvement is about 20 dB relative to the traditional vault emplacement, and 6 m posthole would be the most recommended installation for its high performance cost ratio at current geologic settings. The posthole installation designed in this paper possesses the advantages of easy operation, lower cost and less site occupation, etc., and can be adopted by several upcoming projects which are mainly located in metropolitan areas with high background seismic noise.
2019,40(4): 130-137 收稿日期：2018-12-25
DOI：10.3969/j.issn.1003-3246.2019.04.020
基金项目：中国地震局地球物理研究所中央级公益性科研院所基本科研业务费专项（项目编号：DQJB17B05）；国家重点研发计划（项目编号：2017YFC1500200）
作者简介：刘政一(1987-),男,主要从事地震观测技术研究工作。E-mail:liuzhengyi01@163.com
*通讯作者：袁松湧(1971-),男,高级工程师,主要从事地震观测技术研究工作。E-mail:ysy1@vip.sina.com
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