| 华北盆地Lg波衰减及台站场地响应特征 |
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| 引用本文： | 朱新运.华北盆地Lg波衰减及台站场地响应特征[J].地球科学,2016,41(12):2109-2117. |
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| 作者姓名： | 朱新运 |
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| 作者单位： | 浙江省地震局，浙江杭州 310013 |
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| 基金项目： | 国家自然科学基金重大项目41090291中国地震局星火计划项目XH12023 |
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| 摘 要： | 华北盆地是中国大陆地震活跃区之一，通过地震波衰减及场地响应参数研究该区构造介质属性及台基属性对地震预测预报、灾害评估具有重要意义.基于Lg波谱比的联合反演方法是获得地震波衰减参数及场地响应的有效方法，通过随机重采样方法可以检验解的稳定性.使用华北盆地68个台站记录的2004—2008年的149次地震，震级ML为1.7~5.3的震中距为100~600 km，按信噪比大于2的标准挑选有效垂向记录1 000多条，地震射线较好地覆盖了华北盆地38°N~41°N、114°E~120°E区域.采用2.60~3.65 km/s的速度窗截取Lg波形并转化为频谱，研究频率范围为1~7 Hz，频率间隔0.2 Hz.计算得到的地震波衰减品质因子Q(f)与频率f的关系可表示为Q(f)=125±4.4f0.86±0.03，研究区为低Q0(对应频率1 Hz)，高频率依赖性的构造活跃区.基岩台站对地震波没有表现出明显放大作用，黄土沉积台站低频端比高频端明显放大；场地响应波动较大台站其解的标准偏差也大，说明场地响应的不稳定性体现了台基属性的非稳定性特征.
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| 关 键 词： | 场地响应 衰减 联合反演 解的稳定性 地震 |
| 收稿时间： | 2016-02-11 |
Characteristics of Lg Wave Attenuation and Site Response in North China Basin |
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| Abstract: | North China basin is one of the active seismic regions in the mainland of China. Studies of Lg wave attenuation and site responses can be used for tectonic interpretation, seismic hazard assessment and earthquake prediction. A combined inversion method based on seismic spectral ratios is an effective method for estimating attenuation and site responses. In this paper, a random resampling method is used to check stability of the solutions. Over 1 000 vertical seismograms with signal-to-noise ratio greater than two from 149 events were analyzed. The seismograms are recorded in the distance range of 100-600 km, the earthquakes occurred between 2004 and 2008 in the region and varied in magnitude between 1.7 and 5.3 (ML).The ray-paths cover the region ranging from 38°N to 41°N and 114°E to 120°E.Fourier spectral amplitudes are measured from Lg phases windowed between the group velocity limits 2.60 and 3.65 km/s. The inversion is performed in a frequency range of 1-7 Hz with an interval of 0.2 Hz. The region displays low Q0 and a strong frequency dependence characterized by function Q=125±4.4f0.86±0.03. The result is consistent with the geology of the active tectonic region. The rock sites show small amplification. For soil sites, the amplification of low-frequency waves is higher than that for high-frequency waves. For the stations with more amplification, the corresponding error bar is great. This may indicate that the instability of the bases of these stations reduces the stability of the solution. |
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