Seismic performance evaluations of the existing buildings based on the prediction of the strong ground motions caused by near-field scenario earthquakes

本研究的目的是预测近场地震引起的强烈地面运动，并评估札幌地区现有建筑物的结构损伤。根据特定地区记录地震的震中分布和以往对地质构造的研究，确定了表征假设的近距离札幌地震的断层参数。通过考虑给定的断层参数（如粗糙体位置、断层破裂速度和断层角度）的方差，预测了一组地震动。利用预测的强地面运动进行了一系列地震反应分析。建造了四种类型的建筑模型，即一座木屋，两座混凝土建筑和作为历史重要建筑的前北海道政府办公楼。屋顶上的雪的重量，所应用的建筑规范和基础类型（固定或隔离）的生成被认为是建筑模型。确定了建筑物模型的参数，使模型能反映真实的建筑物的侧向承载力和振动观测得到的动力特性。预测的强地震动对建筑物的影响与日本建筑物抗震设计中所采用的所谓二级地震动基本相同。微凸体的位置对结构损伤的影响最大。仅用地面峰值加速度等一种参数很难对结构的损伤进行评估。模型的侧向承载力和动力特性也很容易改变损伤估计值。建立了近场地震灾害精确评估的程序。

The purpose of the research is to predict the strong ground motions caused by near-field earthquakes and to evaluate the structural damages of the existing buildings in Sapporo region. The fault parameters characterizing the hypothetical close-by Sapporo earthquakes were determined from the epicenter distribution of the recorded earthquakes in the specified region and the previous researches about the geological structure. A set of ground motions were predicted by considering the variance of the specified fault parameters such as the location of asperity, fault rapture velocity and fault angle. A series of seismic response analyses were conducted using the predicted strong ground motions. Four types of building models were constructed, which were a wooden house, two of reinforced-concrete buildings and the Former Hokkaido Government Office Building as a historically important building. The weight of snow on the roof, generation of the applied building codes and foundation types (fixed or isolated) were considered for the building models. The parameters for the building models were determined so that the models can represent the lateral capacity expected as a real building and the dynamic properties obtained from the vibration observation. The influence to the buildings of the predicted strong ground motions were almost the same as the so-called Level-2 ground motions which have been used for the seismic design of the buildings in Japan. The location of the asperity provided the largest influence to the structural damages. It was difficult to evaluate the structural damage using only one type of parameter such as the peak ground acceleration. The estimated damages were also easily changeable by the lateral capacity and the dynamic properties of the building models. The procedure of the precise evaluation of the damages caused by near-field earthquake was established in the research.