地震研究

为探讨辽宁地区地质结构差异对Lg波衰减的影响,将辽宁地区分区为辽西隆起区、下辽河拗陷区、辽东隆起区3个构造单元,基于Lg波谱比法,利用2008—2017年辽宁数字地震台网记录到的308次ML≥2.8～5.6地震的波形资料,在1～7 Hz频率范围内进行联合反演求解Lg波衰减参数与台站场地响应。结果表明:Lg波介质衰减特征分区差异明显,频率依赖指数η差异不大,东西、南北及垂直三分量的品质因子Q(f)在辽西隆起区为176.29～210.55、在下辽河拗陷区为75.18～141.81、在辽东隆起区为161.95～206.10,对应的η分别为0.39～0.9、0.55～0.73和0.50～0.69; 各分区均为低Q0、高η值,地震波衰减程度差异与区域地质构造特征一致; 反演获得的台站场地响应幅值曲线较为平滑,下辽河拗陷地区的台站场地响应幅值大于辽西隆起区和辽东隆起区的场地响应幅值,说明辽宁地区Lg波介质衰减特征与区域浅层沉积层结构有关。

In order to study the effect of the difference of geological structures on Lg-wave attenuation in Liaoning area,we divide the area into three tectonic zones:the Western Liaoning Uplift Region,the Eastern Liaoning Uplift Region,and the Xialiaohe Downwarping Region.Then,we select the waveform data of 308 earthquakes(ML2.0-5.3)during 2007-2018 recorded by the Liaoning Digital Seismic Network,and use the Spectral Ratio method to conduct a joint inversion in the range of 1-7 Hz to calculate the parameters of Lg-wave attenuation and site response.The results show that the attenuation characteristics of Lg-wave are obviously different in these three tectonic regions,while the frequency-dependent indexes(η)have little difference.The Q(f)of the three components(UD,EW,NS)ranges in 176.29-210.55 in the Western Liaoning Uplift Region,in 75.18-141.81 in the Xialiaohe Downwarping Region,and in 161.95-206.10 in the Eastern Liaoning Uplift Region. Respectively,the frequency-dependent index η ranges from 0.39 to 0.90 in the Western Liaoning Uplift Region,from 0.55 to 0.73 in the Xialiaohe Downwarping Region,and 0.50 to 0.69 in the Eastern Liaoning Uplift Region.In the three regions the seismic-wave attenuation is consistent with the regional geological structure.The amplitude curves of the site response at stations are relatively smooth.The site-response amplitude in the Xialiaohe Downwarping Region is larger than that in the Western Liaoning Uplift Region and that in the Eastern Liaoning Uplift Region.This suggests that in Liaoning area the attenuation characteristics of Lg-wave is closely related to the structure of the shallow sedimentary layers.

引言
1 资料的选取与处理
2 计算结果及分析
3 结果稳定性分析
4 讨论
5 结论

图1 辽宁地区构造分区(据万波,钟以章,1997)及Lg波反演分区射线路径示意图<br/>Fig.1 Structural division and seismic ray used for Lg inversion in Liaoning region

图1 辽宁地区构造分区(据万波,钟以章,1997)及Lg波反演分区射线路径示意图
Fig.1 Structural division and seismic ray used for Lg inversion in Liaoning region

表1 辽宁地区分区Lg波衰减参数Q0(f=1 Hz)和η<br/>Tab.1 The Lg wave attenuation parameters Q0(f=1 Hz)and η for three tectonic regions in Liaoning

表1 辽宁地区分区Lg波衰减参数Q0(f=1 Hz)和η
Tab.1 The Lg wave attenuation parameters Q0(f=1 Hz)and η for three tectonic regions in Liaoning

图2 辽西隆起区内使用2.2～3.6 km/s速度窗长截取的ML3.4地震的Lg波(a)及相应波谱(b)<br/>Fig.2 The seismic waveforms(a)and spectra(b)of the Lg waves of ML3.4 earthquake cut in the window between of 2.2-3.6 km/s in the Western Liaoning Uplift region

图2 辽西隆起区内使用2.2～3.6 km/s速度窗长截取的ML3.4地震的Lg波(a)及相应波谱(b)
Fig.2 The seismic waveforms(a)and spectra(b)of the Lg waves of ML3.4 earthquake cut in the window between of 2.2-3.6 km/s in the Western Liaoning Uplift region

图3 辽西隆起区介质衰减参数Q(f)与频率f的拟合图<br/>Fig.3 Relationship between Q(f)and f in the Western Liaoning Uplift region

图3 辽西隆起区介质衰减参数Q(f)与频率f的拟合图
Fig.3 Relationship between Q(f)and f in the Western Liaoning Uplift region

图4 辽东隆起区、辽西隆起地区和下辽河拗陷区的Lg波衰减参数Q(f)与频率的关系<br/>Fig.4 Relationship between Q(f)and f in the Western Liaoning Uplift region,Eastern Liaoning Uplift region and Xialiaohe Downwarping region

图4 辽东隆起区、辽西隆起地区和下辽河拗陷区的Lg波衰减参数Q(f)与频率的关系
Fig.4 Relationship between Q(f)and f in the Western Liaoning Uplift region,Eastern Liaoning Uplift region and Xialiaohe Downwarping region

图5 辽西隆起区(a)、下辽河拗陷区(b)、辽东隆起区(c)内参与评估台站的场地响应特征<br/>Fig.5 The site of station in the Western Liaoning Uplift region(a),the Xialiaohe Downwarping region(b)and the Eastern Liaoning Uplift region(c)

图5 辽西隆起区(a)、下辽河拗陷区(b)、辽东隆起区(c)内参与评估台站的场地响应特征
Fig.5 The site of station in the Western Liaoning Uplift region(a),the Xialiaohe Downwarping region(b)and the Eastern Liaoning Uplift region(c)

图6 辽西地区删除20%地震样本后31个频率对应的Q值拟合图(a)和Q0数据直方图(b)<br/>Fig.6 The frequency-dependent Q values at 31 frequencies(a)and normal distribution of Q0 value(b)when remove 20% of the total data in the Western Liaoning Uplift region

图6 辽西地区删除20%地震样本后31个频率对应的Q值拟合图(a)和Q0数据直方图(b)
Fig.6 The frequency-dependent Q values at 31 frequencies(a)and normal distribution of Q0 value(b)when remove 20% of the total data in the Western Liaoning Uplift region

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备注

引言

1 资料的选取与处理

2 计算结果及分析

3 结果稳定性分析

4 讨论

5 结论

期刊信息