基于区域参数的混合地震动衰减关系

In most countries and regions of the world, strong motion records are not enough to establish regional ground motion attenuation relationships statistically. As a solution, a hybrid ground motion attenuation relationship will be built, in this proposal, to emphasize that the near-fault ground motions are controlled by the sources in large earthquakes. Seismology based ground motion attenuation relationship is the foundation of this research, in which the parameters of regional source spectrum and attenuation are inversed. The ground motion of small earthquakes (M≤6.0) will be evaluated by the point source model, and that of large earthquakes (M>6.0) will be evaluated by the finite-fault hybrid source model. The binding segment will represent the weighted ground motions from the results of these two models. The hybrid attenuation relationship will be optimized as an electric table, and the applicability in seismic zonation will be studied as well. The magnitude range of seismic data will be enlarged and the inversion strategy will be optimized to improve the inversion stability of regional parameters. Further, the corner frequency of the source spectrum model and the Kappa value of the high-frequency filter will be studied to develop the stochastic synthesis method. New scaling laws of global and local source parameters will be given statistically for the hybrid source model, based on the data published in recent years. As an optional attempt, a synthesis method, combining the Green’s function in frequency-wavenumber domain and the equivalent moment tensor source, will be studied to replace the stochastic synthesis method. Thus, the characteristics of crustal medium and the influence of three-dimension velocity structure will be considered, and the ground motions on three directions can be evaluated at the same time.

为破解世界上大多数国家和地区强震观测数据不足、不能直接建立经验性地震动衰减关系的难题，突出大地震近断裂地震动受震源控制的特征，本申请以基于地震学衰减关系为基础，反演区域震源谱参数和衰减参数，用点源模型估计6.0级以下地震的地震动，用有限断层混合震源模型估计6.0级以上地震的地震动，借助电子表格表达的优越性，将二者的结果在过渡范围内加权平均，建立混合衰减关系，进一步考察其在地震区划的危险性计算中的适用性。为提高区域参数反演稳定性，拟扩展测震台网数据震级范围、改善反演策略。为改善地震动随机合成方法，进一步研究震源谱模型中拐角频率和高频截止项中Kappa值的估计方法。补充大量近年新发表的数据，统计混合震源模型的全局和局部震源参数定标律。作为平行的探索，研究用频率-波数域格林函数与等效矩张量源结合的地震动合成方法替换随机合成，以考虑地壳介质的性质和三维速度结构的影响，同时估计三个平动分量地震动。

对世界上大多数国家和地区强震观测数据不足、不能直接建立经验性地震动衰减关系的问题，本项目突出大震近断裂地震动受震源控制的特征，以基于地震学衰减关系为基础，反演区域参数，融合点源模型和有限断层混合震源模型估计的地震动，建立基于区域参数的混合地震动衰减关系，进一步考察其在地震区划的危险性计算中的适用性。为了使物理意义更加明确，探索性地开展基于频率-波数域格林函数（F-K法）合成宽频带地震动场的研究。主要工作包括：（1）深入研究地震动随机合成方法中区域参数和场地项的确定方法。借助测震数据并补充有限强震数据，研究区域参数反演策略；改进震源谱模型的拐角频率，减小子源尺寸影响；研究非弹性衰减项和几何衰减项以及土层场地放大因子的确定方法。（2）补充、更新震源参数数据库，建立有限断层混合震源模型。对走滑、倾滑和全部数据，统计建立经验和半经验的全局和局部参数定标律；以四川地区为例，检验、论证定标律的稳定性和适用性。（3）建立基于区域参数的混合地震动衰减关系。依据区域地震构造判断震源破裂面走向、倾向、倾角等，借助有限断层混合震源模型，合成6.5级以上地震近断层地震动，与点源模型的基于地震学地震动衰减关系结合，研究确定“过渡”带的范围和加权系数，建立用电子表格表达的混合地震动衰减关系；以四川某工程场地为例，考察其在地震危险性计算和地震区划中的适用性。（4）开展基于F-K法合成宽频带地震动场的探索性研究。讨论F-K法有效频带的基础上，与有限断层混合震源模型结合，研究适于该方法的运动学震源模型；搭建基于F-K法合成宽频带地震动场的框架；研究错动量相关拐角频率并以芦山地震为例进行验证；研究F-K法表达速度大脉冲的能力，借助等时线理论，分析其产生机理。