| 有限断层地震波辐射能估算及其在合成强地面运动中的应用 |
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| 引用本文： | 孟令媛,史保平. 有限断层地震波辐射能估算及其在合成强地面运动中的应用[J]. 地震学报, 2011, 33(5): 637-649 |
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| 作者姓名： | 孟令媛 史保平 |
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| 作者单位： | (中国北京100049中国科学院研究生院地球科学学院) |
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| 基金项目： | 中国科学院知识创新工程重要方向项目(KZCX2-YW-Q08-2)资助 |
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| 摘 要： | 对有限断层地震波能量辐射的估算通常采用断层面上子源能量的逐点求和方法。基于Brune圆盘模型，Anderson推导出有限断层地震波能量辐射S波的求解公式，即 ，其中 为断层面上地震矩， 为剪切模量， 和 分别为动态应力降和静态应力降，并指出在复合震源模型强地面运动预测应用中 以满足能量守恒。Rivera和Kanamori则从能量辐射表象定理出发，给出了有限断层中辐射能量的积分表达式，明确地指出了逐点求和所存在的问题。依据该积分表达式，本文推导出了复合源模型中新的辐射能完整的求解方法，指出Anderson方法实为断层面上点源辐射能量的简单叠加求和，后者则充分考虑了断层面上任一点在任一时刻能量传播过程中受到的断层面上所有位移破裂路径的交互影响。以1976年唐山7.6地震为例，应用上述方法分别计算了有限断层模型的辐射能量及近场强地面运动，如质点运动加速度，速度。结果表明如果模型参数满足 时，由本文给出的求解方法计算所得到的地震波辐射能已远远超出实际的辐射能量值，直接导致了对近场强地面运动参数如质点速度、加速度等的过高估算。因此，Zeng等和Anderson工作的局限性是非常明显的:地震矩守恒以及非物理的 无法准确地预测近场地面运动。未来工作中，对于有限断层模型的建立，在地震矩守恒这一约束条件的基础上，远场和近场能量解（或视应力）将可作为另一个重要的约束条件，为强地面运动的模拟提供一个更为恰当的求解方案。
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| 关 键 词： | 有限断层 辐射波能量 应力降 复合震源模型 强地面运动 |
Ground motion prediction based on estimated seismic energy radiated from finite fault |
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| Meng Lingyuan Shi Baoping. Ground motion prediction based on estimated seismic energy radiated from finite fault[J]. Acta Seismologica Sinica, 2011, 33(5): 637-649 |
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| Authors: | Meng Lingyuan Shi Baoping |
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| Affiliation: | (College of Earth Science, Graduate University of Chinese Academy of Sciences, Beijing 100049, China) |
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| Abstract: | The radiated seismic energy strongly depends on how the rupture propagates during the earthquake. In this study, we calculated the radiated energy and apparent stress, from the known slip distribution described by Brunersquo;s source function which is commonly used in the strong motion modeling, resulting from the composite source model. A new technique based on the far-field energy integrand over a simple finite fault is developed to estimate S-wave energy radiation with associated composite source model. Comparing with point source summation proposed by Anderson in which , where is the energy radiated by S-wave, and are the scalar seismic moment and shear rigidity, respectively, and are the static and dynamic stress drops, respectively, the new result is numerically given by , where (k=1, 2, 3,hellip;, n) are the subevent size, CS and q are constants which can be determined from seismic moment conservation used previously by Zeng et al. and Anderson. As Rivera and Kanamori pointed out that, in such case, the integration of the energy flux from any point on the fault depend not only the slip function at such point, but also on the slip function everywhere over the fault plane. Moreover, we discussed the frictional overshoot and undershoot behaviors inherited from Andersonrsquo;s consideration and our current solution for the composite source model, and the scaling relation of radiated energy to the ratio of given by Anderson may be incorrect in the source energy estimation. For comparing purpose, we developed composite source model to simulate the 1976 Mw7.6 Tangshan Earthquake and calculate the radiated S-wave energies based on theAndersonrsquo;s solution and our new solution. The results show that, forAndersonrsquo;s solution, the energy conservation occurs when , and the corresponded near-fault particle velocity or PGV (peak ground velocity) reaches about2m/s which are much higher than real observation. In contrast, the result derived from our new solution indicates that the energy conservation occurs at which is similar to the theoretical consideration of ( is called apparent stress and ), and the corresponded near fault PGV is about 0.9~1.3m/s which is much smaller than that fromAndersonrsquo;s solution. We suggest that, for the strong motion simulation, the seismic moment alone is insufficient to quantify the ground motion level, the radiated energy or apparent stress derived from earthquake source inversion should be an additional constraint condition in the future development of numerical algorithm of strong motion prediction. |
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| Keywords: | finite fault radiated energy stress drop composite source model strong ground motion |
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