软土层地区地震仪安装效果比对研究  

Comparisons between different installations of seismographs at soft soil site

作　　者：许卫卫[1] 袁松湧[1] 徐善辉 刘政一[1] 徐天龙 宋丽莉[1] 董传杰 XU WeiWei;YUAN SongYong;XU ShanHui;LIU ZhengYi;XU TianLong;SONG LiLi;DONG ChuanJie(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;Beijing Long-March Launch Vehicle Equipment Technology Co.,Ltd.,Beijing 100076,China)

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]北京长征火箭装备科技有限公司,北京100076

出　　处：《地球物理学报》2023年第5期2069-2081,共13页Chinese Journal of Geophysics

基　　金：国家重点研发计划(2017YFC1500201);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(DQJB22Z01-05);国家自然科学基金(42074050)联合资助。

摘　　要：随着ChinArray等大型地震观测项目逐渐推进,一些台站不得不安装在软土层等较高背景噪声区域,研究这些区域中不同类型地震仪在不同安装方法之间的背景噪声水平差异,对于提高观测数据质量、选取观测仪器类型、研制地震仪器等问题具有重要意义.本文在北京通州西集地震台,通过一系列比测实验研究了宽频带地震仪在不同安装深度、安装方式以及保温隔离防护方式下的安装效果差异,结果表明:在0.05~1 Hz的海浪脉动噪声频段附近,所有参与比测地震仪的三个分量背景噪声水平均高度一致,符合远场海浪脉动信号的特点;在低于0.05 Hz的低频段范围,背景噪声主要和地震计附近的温度变化及气流扰动环境相关,增加安装深度和采取保温隔离防护措施效果类似,其中垂直向对保温隔离防护措施更为敏感,比如1~2 m深度安装的地震计在妥善进行保温隔离措施后可获得和283 m井下地震计类似噪声水平,水平向由于存在地倾斜噪声,当大幅度增加安装深度时仍可有效降低噪声水平;在高于1 Hz的高频段范围,背景噪声衰减和地下介质岩性相关,软土层地区地下10 m以内随安装深度增加背景噪声水平衰减非常有限.另外,我们还研究了宽频带、短周期、节点式等不同类型地震仪的安装效果差异,结果表明:在软土层地区的地震观测,需要针对不同观测目的选择合适的地震仪;在密集台阵观测中,不同类型仪器的组合观测是更科学的方式.With the gradual progress of large-scale seismic observations such as the ChinArray project,some seismic stations have to operate at the soft soil site with much high background seismic noise.Studying the installation effects of seismographs in these areas is of great significance for improving seismic data quality,selecting suitable instruments and developing seismometers.At Xiji seismic station in Tongzhou,Beijing,We studied the noise performances of different broadband seismometers with several installation depths,installation methods and various insulation measures.Our results show that the noise levels of all three components from all seismometers are highly identical at the frequency domain of microseisms,which is consistent with the far-field characteristic of this signal.For the low-frequency part(<0.05 Hz),the background seismic noises are closely related to the surrounding temperature variation and air perturbation around the seismometer.It has similar effects to either increasing the installation depth or adopting reasonable insulation measures for the seismometer.The vertical component of the seismometer installed at 1~2 m depth with appropriate insulation measures could reach a similar level to that of the borehole seismometer installed at 283 m depth.There would still be a significant improvement in noise performance for the horizontal components with the increased installation depth because the noise is related to the tilt noise.For the high-frequency part(>1 Hz),there are slight decreases in noise levels within 10 m installation depths because the attenuation of the noise level in this frequency band is much related to the soil or rock type around the seismometers.Besides,We studied the noise performances of three seismometer types:broadband,short-period and node sensors.Our results show that we must select appropriate sensors based on various observation goals.In dense seismic observation,combining the node,short-period and broadband seismographs is a more scientific and reasonable way.

关 键 词：宽频带地震计 软土层地区 地震仪安装 浅井式地震计 安装效果 

分 类 号：P315[天文地球—地震学]