基于H/V谱比法的重庆测震台网场地响应研究
杨亚运,汪建,李翠平,马伟

(重庆市地震局,重庆 401147)

H/V谱比法; 场地响应; 台基形式; 重庆地区

Site Response of the Chongqing Seismic Networks Based on the H/V Spectral Ratio Method
YANG Yayun,WANG Jian,LI Cuiping,MA Wei

(Chongqing Earthquake Agency,Chongqing 401147,China)

H/V spectral ratio method; site response; platform form; Chongqing area

DOI: 10.20015/j.cnki.ISSN1000-0666.2024.0047

备注

利用重庆测震台网36个子台地脉动噪声数据,采用H/V谱比法计算分析场地响应。根据各台站0.5～20 Hz场地响应曲线形态特征,将这些子台分为平坦类、低频放大类、中频放大类、中频衰减类和高频放大类。结合7个钻孔应变同址观测台站地质剖面图,分析了浅层地质构造对台站场地响应的影响,结果表明:台基岩性差异和分层结构对场地放大效应有直接影响,台站局部低密度介质会造成低频段(0.5～1 Hz)的场地放大效应,而岩性单一的地下结构场地放大效应不明显。对比3个台基改造台站在改造前后的场地响应曲线,发现台基观测形式的改变对台站场地响应会产生实质性的影响,地震计墩加高后的独立柱体结构,明显增大了中高频段场地放大效应。重庆地区场地响应等值线分布与区域地形地貌之间无必然联系,但台基局部地势和所处山体的位置会影响观测频带范围内场地响应曲线表现形态。综合来看,台基岩性差异和工艺水平、浅层地质构造和介质密度、局部地形特征和山体部位等均会影响台站场地响应的表现形式。
Using the microseismic noise data recorded by 36 sub-stations of the Chongqing Seismic Networks,the site response of each of these sub-stations is calculated by the method of H/V spectral ratio.According to the form of the site response curves of these sub-stations within the 0.5-20 Hz frequency band,these sub-stations are divided into five categories:stations with flat curves,stations with low-frequency-amplification curves,stations with intermediate-frequency amplification curves,stations with the curves of intermediate-frequency attenuation and high-frequency amplification.By the help of the geological profiles of the borehole strain monitoring at 7 stations,the influence of the shallow geological structure on the site response of the sub-stations is analyzed.results show that the lithological difference and layered structures on the station site have a certain impact on the site response of the seismic stations.Partial low-density media around the stations will cause site amplification effect in low frequency band(0.5-1 Hz),while the site amplification effect of structures with single lithology is not obvious.Comparing the site response curves recorded by 3 reconstructed stations in 2019 and 2021,it is found that the change of the seismometer pillar will have a substantial impact on the site response curves; the independent pillar has obvious site amplification effect.In Chongqing area,the site response contour lines are not necessarily related to the regional terrain and geomorphology,but the small-scale terrain around the station and the location of the station in the mountains will affect the form of the site response curves within the frequency band.In conclusion,the lithology underneath the station,the differences of the shallow media,the construction quality of the seismometer pillar,the regional terrain,and the shallow geological structures all affect the site response at the stations.