陕西地区近震震级与介质衰减、场地响应的关系  

The relationship between local earthquake magnitude,medium attenuation and site response in Shaanxi

作　　者：张媛媛[1] 邱玉荣[1] 赵韬[1] 杨宜海 苏丽娜 ZHANG Yuanyuan;QIU Yurong;ZHAO Tao;YANG Yihai;SU Lina(Shaanxi Earthquake Agency,Xi’an 710068,China)

机构地区：[1]陕西省地震局,西安710068

出　　处：《地震地磁观测与研究》2022年第6期15-22,共8页Seismological and Geomagnetic Observation and Research

基　　金：地震科技星火计划(项目编号:XH20056);陕西省自然科学基础研究计划(项目编号:2022JQ-225)。

摘　　要：利用陕西测震台网51个台站2012—2019年所记录的91个地震,基于遗传算法和互相衔接的三段几何衰减模型,采用Athinson方法计算得到陕西地区介质品质因子Q值与频率f的关系为Q(f)=698.4f^(0.2828)。考虑到陕西地区介质横向不均匀性强烈及天然地震分布特征,反演了秦巴山区和关中盆地的介质品质因子,分别为Q1(f)=665.5f^(0.2671)和Q2(f)=756.2f^(0.3443)。采用Moya方法反演陕西测震台网46个固定台站的场地响应。TOCH台在1—6 Hz,HUAX台在3—20 Hz,GST台在7—20 Hz,FXI台在2—20 Hz,LNA台在3—10 Hz,均表现出了明显的放大作用。根据波形数据和观测报告,计算出2002—2019年陕西测震台网所记录到的2309次ML≥2.0近震单台震级测定值与台网平均震级的差,得到震级偏差的分布图像。结果显示:关中盆地单台震级普遍偏大,这与盆地表层松软沉积层对入射波的放大作用有关。秦巴山区单台震级普遍偏小,与秦巴山区相对低Q0值、地震射线途经该区域时能量大幅度衰减有关。HUAX台、LNA台、TOCH台、GST台、FXI台、FUPI台的震级偏差是一个较大的正值,这与台基对震级的放大作用一致。由统计结果可知,区域地震振幅衰减受上地壳构造、非弹性衰减及场地响应共同影响,其中,场地响应增益的影响最大。Based on the genetic algorithm and the interconnected three-stage geometric attenuation model,the relationship between the media quality factor Q value and frequency f,which is Q(f)=698.4f^(0.2828),is calculated by using the Athinson method and 91 earthquakes recorded by 51 stations of Shaanxi Seismic Network during 2012-2019.Considering the strong transverse inhomogeneity of medium and the distribution characteristics of natural earthquakes in Shaanxi,the medium quality factors of Qinba mountains and Guanzhong Basin are inversed as Q1(f)=665.5f^(0.2671)and Q2(f)=756.2f^(0.3443)respectively.The Moya method is used to invert the site responses of 46 fixed stations in Shaanxi Seismic Network.TOCH at 1-6 Hz,HUAX at 3-20 Hz,GST at 7-20 Hz,FXI at 2-20 Hz,and LNA at 3-10 Hz all show obvious amplification.According to the waveform data and observation reports,the difference between the measured single station magnitudes of 2309 local earthquakes with ML≥2.0 recorded by Shaanxi network from 2002 to 2019 and the average magnitudeis calculated,and the distribution image of magnitude deviation is obtained.The results show that the single station magnitudes in Guanzhong Basin are generally larger,which may be related to the amplification of the incident wave by the soft sedimentary layer on the surface of the basin.The single station magnitudes in Qinba mountains are generally small,which may be related to the relatively low Q0 value in Qinba mountains and the great attenuation of seismic energy when seismic rays pass through this area.The magnitude deviation of HUAX,LNA,TOCH,GST,FXI and FUPI stations is a large positive value,which is consistent with the obvious amplification effect of the site responses on the magnitude.According to the statistical results of this paper,the regional seismic amplitude attenuation is affected by the upper crust structure,inelastic attenuation and site response,especially the gain of site response.

关 键 词：Q值 场地响应 震级偏差 

分 类 号：P315.32[天文地球—地震学]