Evaluation of Ground Motion for Urban Structures by Near Field Earthquake

为减轻城市地震灾害，在城市设施抗震设计和城市规划中必须考虑近场地震动的影响。这些过程可以包括设计地震运动和/或地震荷载的规范，以及地震微区划图的开发。我们小组的研究课题旨在从工程角度促进这一进程。该小组的专题又细分为以下三个分专题。每个子主题最初被分配给我们小组的12名研究人员，但大多数研究人员不仅参与了一个子主题，而且还参与了两个或三个。研究了近场地面运动及其对土压力、液化势和地面位移的影响，以获得专门用于建筑物、桥梁、隧道和埋地管道等城市设施结构设计的一般准则。最差近场运动及其影响在结构设计和灾害管理中，我们必须注意这样或那样超出标准设计运动和载荷的特殊情况。这一分主题下的研究包括最坏情况的原因和影响，如所谓的地震灾害带和对大坝等重要建筑物的近场影响。地震微区划由于场地局部效应，地面运动强度不同，我们应该考虑到城市规划和生命线系统设计的多样性。在考虑了震源和路径效应以及地形和地质不规则性的情况下，对1995年日本深渊-南方地震的高烈度分布进行了评估，并发展了一种利用微震测量来检测局部场地效应的有效方法。

To mitigate urban earthquake disaster, we have to take in account effects of near-field ground motion in earthquake resistant design of urban facilities as well as in urban planning. Such process may include specification of design earthquake motion and/or seismic loading, and development of seismic micro-zoning maps. The research topic of our group aims to facilitate the process from engineering points of view. The topic of this group was sub-divided into the following three sub-topics. Each sub-topic was originally assigned to 12 researchers consisting of our group, but most researchers have involved in not only one sub-topic but also two or three.1. Input Ground Motion and Seismic Loading.Near-field ground motion and its effects on earth pressure, liquefaction potential and ground displacement have been studied to obtain general guidelines specifically used for structural design of urban facilities such as buildings, bridges, tunnels, and buried pipelines.2. Worst Near-field Motion and Its EffectsIn structural design and disaster management, we have to pay attention to special cases where standard design motion and loading are exceeded in somehow or other. Studies under this sub-topic have included causes and effects of worst cases such as the so-called seismic disaster belt and near-field effects on important structures like dams.3. Seismic Micro-zonationSince ground motion intensity varies due to local site effects, we should bear in mind the variety in urban planning and design of lifeline systems. The distribution of higher seismic intensity in the case of the 1995 Hyogoken-nanbu earthquake has been evaluated taking into account source and path effects as well as topographical and geological irregularities, and an effective procedure has been developed to detect the local site effects by means of microtremor measurement.