Ground Motion of Subduction Earthquakes for Seismic Design

1. 智利中部强震遗址的现场调查。在1985年智利中部地震中有强震记录的9个强震点进行了微震阵观测，估计了这些强震点的横波速度剖面。在圣地亚哥也观察到微震，那里已经开发了强震阵列。这些结果有助于全面了解智利中部强震遗址的特征。强震数据库的建立建立了智利和日本地震强震记录数据库。数据库中收录了大约100个智利数据和500多个日本数据。数据库中还包括了强震站点的站点特征信息。俯冲地震强震记录的分析对数据库中的强震记录计算了峰值加速度、速度和反应谱等地震动参数。分析了震源、传播路径和场地对地震动参数的影响。结果表明：(1)场地效应在较长周期内显著；(2)地震动振幅随震源深度的增加而增大；(3)大洋板块地震产生的地震波比大陆板块地震产生的地震波更强；(4)大洋板块大地震产生的地震波衰减较小。从地震震级、断层距离、震源深度和地面平均横波速度等方面提出了预测峰值加速度和速度的经验关系。大俯冲地震产生的地面运动被认为具有更长的周期内容、更小的衰减衰减和更深的地震产生的更大振幅。

1. Site investigation at strong-motion sites in the central part of Chile.At 9 strong-motion sites where strong-motion records have been obtained in the 1985 Central Chile earthquake, microtremor array observations were conducted to estimate the shear-wave velocity profiles at the sites. The microtremors were also observed in Santiago where the strong-motion array have been developed. The results contributed to complete information about site characteristics at strong-motion sites in the central part of Chile.2. Construction of strong-motion databaseThe database of the strong-motion records from Chilean and Japanese earthquakes were constructed. About 100 Chilean data and more than 500 Japanese data were compiled in the database. In the database, imformation about site characteristics of the strong-motion sites were also included.3. Analysis of strong-motion records from subduction earthquakesGround motion parameters such as peak ground acceleration, velocity and response spectra were computed for strong-motion records in the database. The source, propagation path and site effects on the ground motion parameters were analyzed. The results indicate that (1) site effects are significant in longer periods, (2) the amplitude of ground motion increases with increase of the source depth, (3) earthquakes in the ocean plate tend to generate stronger seismic waves than those in the continental plate, and (4) attenuation of seismic waves from large earthquakes in the ocean plate is smaller.4. Evaluation of ground motion characteristics from large subduction earthquakesEmpirical relationships for predicting peak acceleration and velocity were proposed in terms of earthquake magnitude, fault distance, source depth, and average shear-wave velocity of ground. It was also pointed out that ground motion from large subduction earthquakes is considered to have longer-period contents, smaller attenuation decay, and larger amplitudes from deeper events.