考虑断层各分段间相互作用的近场强地震动模拟方法研究

The main reason lead to structure damage are rupture directivity effects, the hanging wall/footwall effects and pulsing effects of near-source ground motion. So, how to simulate the near-source strong ground motion which engineering site may be subjected to, and providing design seismic accelerogram, are the objective requirement of anti-seismic analysis and challenges in engineering construction. However, there are significant deficiencies in current near-source earthquake simulation methods, such as the multi-fault rupture model could not be reflected, the impact of the phase spectrum and parameters uncertainty on acceleration time history had not be considered. In this project, the multi-fault rupture model, interactions of inter-faults parts, calculation method of radiation energy, and as well as phase spectrum and ground motion spatial distribution pattern will be studied, and accordingly, the multi-fault rupture source model, the simulating ground motion spatial distribution model, and the coherence function model will be established, and the methods of determination radiation energy and phase spectrum will also be proposed. Thus, ground motion simulation method, which multi-faults inter-parts interaction will be taken into account, will be proposed. Finally, by using record datum, the rationality and applicability of the proposed method will be demonstrated. This project will provide both the method and model base of determining synthesis ground motion time history for structure anti-seismic analysis. The results of this project have both social and economic benefits in preventing severe seismic catastrophe, improving structure anti-seismic capacity, and protecting people's lives and properties safety.

近场地震动的破裂方向性、上下盘效应和脉冲效应等是引起结构破坏的重要原因。如何模拟工程场地可能经受的近场强震动，提供设计地震加速度图，是结构抗震分析的客观要求，也是工程建设中必须面对的严峻挑战。本项目针对目前近场强地震动模拟中存在震源模型不能反映多断层破裂模式、模拟地震时程能量分配不合理等问题，导致模拟时程失真于地震记录的现状，拟就多断层破裂模式、断层各分段间相互作用、辐射能和相位谱确定方法、地震动空间分布规律等方面展开深入研究，以期建立多断层破裂震源模型、地震动空间分布函数和相干函数模型，给出地震辐射能和相位谱的计算方法，提出一套考虑断层各分段间相互作用的近场强地震动模拟方法，并通过与记录资料的对比分析论证所提方法的合理性和适用性。项目的开展将为结构抗震分析提供确定地震动时程的方法和模型依据，研究成果在防止严重地震灾变、提高结构抗震能力、保障人民生命财产安全等方面具有重要的社会和经济效益。

如何模拟工程场地可能经受的近场强震动是结构抗震分析的客观要求和工程建设中必须面对的严峻挑战。针对目前近场强地震动模拟中存在震源模型不能反映多断层破裂模式的现状，开展了多断层破裂模式地震动参数的特征分析、震源模型及其模型参数的敏感性分析、地震动时程能量分布规律，能量分布和相位谱对合成时程的影响、地震动空间分布规律、地震动持时的特征分析、地震动强度指标的衰减特性、地震动强度指标的与结构地震响应位移的相关性分析等的研究。揭示了多断层破裂模式下地震动三要素的特征及地震动的空间分布规律，能量分布形式、相位谱的选取、震源模型参数的取值等对人工合成地震加速度时程的影响规律，与结构地震响应位移量密切相关的地震动强度指标。对比分析了单、双平稳地震动参数的衰减规律、加速度时程旋转前后持时的相关性和强度指标与结构响应位移的相关性、记录时程和人工合成地震动时程持时的空间分布规律，建立了震源谱模型、双平稳地震动三要素和强度指标的衰减模型、沿深度变化的地震动相干函数模型，提出了多断层破裂模式的近场地震加速度时程合成方法。