| 首都圈地区地震视应力的计算及空间分布 |
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| 引用本文： | 杨志高,张晓东.首都圈地区地震视应力的计算及空间分布[J].地震,2009,29(4). |
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| 作者姓名： | 杨志高 张晓东 |
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| 作者单位： | 1. 中国地震局地震预测研究所,北京,100036
2. 中国地震台网中心,北京,100045 |
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| 基金项目： | 中国地震局行业专项，国家科技支撑计划 |
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| 摘 要： | 本文计算了首都圈地区2003年9月到2007年12月117个 M_L>2.5地震的视应力,计算视应力的两个参数地震矩( M_0)和地震辐射能量( E_s)都是通过分析地震波形得到. 首先用多重窗FFT获得观测谱,在扣除仪器响应后对其进行几何扩散和非弹性衰减校正. 几何扩散使用Gail提出的三分段几何模型,非弹性衰减用随频率变化的Q值来表征. 之后通过遗传算法找到一组Brune圆盘模型下的低频水平( Ω_0)和拐角频率( f_c),使得它们的理论震源谱和校正过的观测谱残差最小. 通过Ω_0可以得到 M_0,通过对校正过的观测谱求积分再加上有限仪器响应带宽补偿可以得到 E_s,最后就能通过 M_0和 E_s获得视应力. 计算结果与先前的一些研究比较符合:视应力随地震矩不存在系统变化;f_c随着 M_0变化和定标率 M_0∝f_c~(-3)符合较好;M_0和 M_L的关系与定标率lg( M_0)=1.20 M_L+10.0符合较好. 最后给出了视应力的空间分布,结果显示视应力在邢台、 唐山和晋冀蒙交界处的空间分布有不同的特征. 还显示在2006年7月发生 M 5.1地震的文安北东方向有一个较大的视应力值,唐山地区视应力从南西到北东方向大体是增加的.
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| 关 键 词： | 视应力 地震矩 拐角频率 辐射能量 首都圈 |
Computation of Apparent Stress and its Spatial Distribution in the Capital Region of China |
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| YANG Zhi-gao,ZHANG Xiao-dong.Computation of Apparent Stress and its Spatial Distribution in the Capital Region of China[J].Earthquake,2009,29(4). |
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| Authors: | YANG Zhi-gao ZHANG Xiao-dong |
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| Institution: | YANG Zhi-gao1,ZHANG Xiao-dong2(1.Institute of Earthquake Science,CEA,Beijing 100036,China,2.China Earthquake Network Center,Beijing 100045,China) |
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| Abstract: | In this paper, we calculate seismic apparent stresses for 117 earthquakes occurred from September 2003 to December 2007 in the capital region of china, with the minimum magnitude limit of M_L2.5. The spectral technique was used to estimate the low frequency flat level ( Ω_0) and the corner frequency ( f_c) of Brune ω~2 model and radiated energy ( E_s). We first use the multi-window FFT to obtain the observed spectrum, and then after extracting the instrument response it is corrected for geometry spreading and attenuation. For geometry spreading correction, Gail′s three section geometry spreading model was used. The frequency-dependent Q value was used for inelastic attenuation correction. The genetic algorithm was applied to determine a pair of f_c and Ω_0 of Brune ω~2 model, which yields the least deviation between theoretical ω~2 model and corrected spectra. Seismic moment ( M_0) was calculated from Ω_0, and E_s was obtained by integrating corrected spectral with limited bandwidth compensation. Apparent stress can be calculated from M_0 and E_s. The results turn out to fit well with some previous work, the apparent stress does not vary with earthquake size;f_c decreases with M_0 following the scaling law M_0∝f_c~(-3);M_0 and M_L follows the scaling low lg( M_0)-1.20 M L+10.0. In the end, we give the spatial distribution of the calculated apparent stress. The result indicates that the value of earthquake apparent stress concentrated in three zones of the capital region and their spatial distribution characteristics are different. There is a high value in 2004 northeast of Wen'an region where M_S5.1 earthquake occurred in Jul 2006, and apparent stress in the Tangshan region on the whole increases from Southwest to northeast. |
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| Keywords: | Apparent stress Earthquake moment Corner frequency Radiated energy Capital region |
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