单台地震动不确定性分析及场地效应研究

Seismic hazard analysis techniques in China recently lag greatly behind the world pace for decades, which becomes the weakness for engineering aseismic techniques development. Single-station ground-motion analysis, i.e., a key issue in seismic hazard analysis, presently attracts more and more interests of earthquake researchers and engineers worldwide. In this proposal, overcoming the paucity of single-station earthquakes records in previous work, a sizable set of high-quality seismic strong motion data recorded in the strong earthquake sequences of 2010 and 2012 in the Canterbury, New Zealand, is selected. Following recent, well established concepts and approaches of residual analysis of ground motion prediction equations (GMPE), the components of single-station standard deviations are systematically analyzed, and then the uncertainties associated to GMPE are rephrased to establishing criteria to evaluate the uncertainties in GMEPs. Pinpointing the physical meaning of site terms, correlations of site terms with respect to site seismic response are revealed so that a new method to effectively assess site seismic response based on single-station records can be proposed. Imbedding single-station standard deviation into PSHA practice, a new non-ergodic PSHA approach is proposed to eliminate ergodic assumption. Carrying out the approach on the modeling benchmark of Canterbury alluvial plain, which is built according to local geotechnical, geological and seismotectonic documents, the non-ergodic PSHA results are investigated. Consequently, the proposed approach and obtained remarks can be extended into seismic hazard analysis for typical areas in China.

我国工程抗震技术研究中地震危险性研究水平近年来明显落伍，成为工程抗震技术研究的薄弱环节，其中的关键问题单台地震动研究是目前地震危险性研究备受学者关注的新课题。本项目中，克服以往研究中单台地震记录稀缺的局限，选取新西兰2010-2012年地震中高质量的强震记录，采用近年来提出的单场地震动变异性概念及分析方法，给出单台地震动变异性的描述，正确认识地震动衰减关系（即GMPE）中的不确定量，重新定义GMPE中的不确定量的评估准则；剖析场地特征项的物理含义，给出场地特征项与场地地震响应的对应关系，建立通过单台地震记录评估场地效应的方法；以新西兰Canterbury地区地震地质构造为模板，将单台地震动变标准差值应用到场地的地震危险概率分析方法中，探讨Canterbury地区消除各态历经性影响的PSHA计算结果，提出单台地震动标准差的非各态历经地震危险性概率分析方法，并拓展到我国典型地区地震危险性评价.

单台地震动不确定性研究是目前地震危险性分析方法中备受学者关注的课题，也是非各态历经性PSHA方法发展的关键环节。本项目通过单台强震数据分析，研究单台地震动不确定性及场地效应，主要研究结论包括：（1）场地修正的平均单台地震动均方差相对于基于各态历经性假定的GMPG均方差降低了月50%，且在宽频带范围内基本稳定在0.2水平，将单台地震动均方差取代GMPE均方差，更够好地评估场地地震动不确定性以及场地地震危险性；（2）首次引进场地反应项的概念，剖析了其物理意义，提出了场地反应项修正GMPE预测地震动参数的方法，其将场地效应考虑到地震动参数估计中，相对于地震动预测方程的预测值，场地反应项修正的地震动参数更吻合实际观测值；（3）提出了特定场地非各态历经性PSHA分析方法，将单台地震动均方差取代GMPE的均方差，或缺少强震数据的地区取值0.2，其更合理地估计场地地震动的不确定性；（4）提出了场地条件校正的PGA快速评估方法，并建立了指标标准，可为地震预警和烈度速报提供技术支撑。本项目研究共发表论文9篇（含2篇待刊），其中SCI/EI检索论文8篇。