地震背景噪声HVSR方法在安徽明光城市场地响应特征和活断层探测中的应用  

Application of horizontal-to-vertical spectral ratio on prospecting urbansite response and subsurface active faults in Mingguang,Anhui province

作　　者：倪红玉[1,2,4,5] 张若晗 李俊伦 黄显良 郑海刚[1,2,4,5] 洪德全 缪鹏[1,2,5] 彭刘亚 鲍子文[1,2,5] NI HongYu;ZHANG RuoHan;LI JunLun;HUANG XianLiang;ZHENG HaiGang;HONG DeQuan;MIAO Peng;PENG LiuYa;BAO ZiWen(Anhui Earthquake Agency,Hefei 230031,China;Mengcheng National Geophysical Observatory,Mengcheng Anhui 233500,China;School of Mathematics and Center of Geophysics,Harbin Institute of Technology,Harbin 150001,China;School of Eath and Space Sciences,University of Science and Technology of China,Hefei 230026,China;Anhui Key Laboratory of Subsurface Exploration and Earthquake Hazard Risk Prevention(in prep.),Hefei 230026,China)

机构地区：[1]安徽省地震局,合肥230031 [2]安徽蒙城地球物理国家野外科学观测研究站,安徽蒙城233500 [3]哈尔滨工业大学数学学院、地球物理中心,哈尔滨150001 [4]中国科学技术大学地球和空间科学学院,合肥230026 [5]地下结构探测与震灾风险防范安徽省重点实验室(筹),合肥230026

出　　处：《地球物理学报》2023年第11期4552-4571,共20页Chinese Journal of Geophysics

基　　金：中国地震局地震科技星火计划(XH23020YA);安徽蒙城地球物理国家野外科学观测研究站联合开放基金(MENGO-202307);安徽省自然科学基金(2108085MD137);中央高校基本科研业务费专项资金(WK2080000141)共同资助。

摘　　要：本文利用跨郯庐断裂带明光段东边界一条密集测线的波形数据,计算了该测线133个台站的HVSR曲线,获得了剖面的峰值频率.基于计算的HVSR曲线,我们采用粒子群算法反演了浅层地壳的S波速度结构,并通过地质构造、钻孔资料、浅层地震反射剖面和频散曲线反演结果等验证其可靠性,进而对郯庐断裂带明光段的沉积格局、东界两条主干断裂的空间展布和活动性特征进行分析讨论,得出如下结论:(1)测线下方HVSR剖面呈现复杂的双峰、多峰形态,其场地分类均为Ⅱ类中硬土,但峰值频率变化较大,应关注西侧凹陷区对强地面震动的放大效应;(2)HVSR反演S波速度结构揭示的土石界面与钻孔结果较为一致,其分布形态、趋势与浅层地震反射剖面结果高度吻合,且刻画了主动源未能刻画的风化基岩-未风化基岩界面;(3)HVSR反演S波速度结构刻画的郯庐断裂带东界两条断裂的空间展布、活动性等特征与钻孔、浅层地震、频散反演和地质构造等结果较为一致,并揭示池河—太湖断裂的活动性强于嘉山—庐江断裂,可能为活动断裂.上述研究结果表明HVSR方法可以应用于城市场地响应特征、浅层沉积结构和隐伏活断层探测等.A dense survey line consisting of 133 stations was deployed in Mingguang,Anhui Province,which spanned across two main faults,namely the Jiashan—Lujiang fault and the Chihe—Taihu fault,along the eastern boundary of the Tan-Lu fault zone.Based on the ambient noise data,we calculated the horizontal-to-vertical spectral ratios(HVSR)for the 133 stations,and the peak frequencies along the profile were obtained.With the obtained HVSR,we then inverted for the near-surface S-wave velocity structures using a particle swarm optimization algorithm,and the reliability of the result was verified by comparing the HVSR result with the geological,borehole drilling,active-source imaging and ambient noise dispersion results.The sedimentary structure along the profile,as well as the layouts and activities of the two main faults were further analyzed.It is found that:(1)though the HVSR profile varies greatly and presents complex dual and multiple peaks,the site responses were all classified as medium-hard soil of typeⅡ;attentions should be paid to the amplification effect of the western depression for strong ground motions;(2)the soil-rock interface revealed in the inverted S-wave velocity structure is relatively consistent with the drilling results,and is also highly consistent with the reflection profile using the active sources;in addition,the interface between the unconsolidated and consolidated bedrocks which could not be identified by the active-source profiling is also revealed;(3)the delineation of the two faults by the S-wave velocity structure using HVSR agrees well with the profiles using borehole data,active seismic data,ambient noise dispersion data,as well as geological data.The Chihe—Taihu fault may be an active fault,and it is more active than the Jiashan—Lujiang fault.Our study indicates that HVSR method can be used in prospecting the characteristics of site responses,shallow velocity structures,and hidden active faults in the urban areas.

关 键 词：HVSR 场地响应特征 城市活断层 浅层速度结构 郑庐断裂带 

分 类 号：P315[天文地球—地震学]