Study on basement of earthquake input motion under the Nobi plain based on earthquake observation

本文简要介绍了名古屋市三野温泉井的调查和地震观测结果，以及大比平原的微震阵测量和地震模拟分析。三诺钻孔调查与地震观测证实基岩为坚硬的花岗岩；v =2.8km/s， San-no井底深度约670m，沿井方向的PS测井也获得了s波速度分布。我们在基岩和地表观测到许多地震记录，包括在诺比平原下发生的微地震。利用微震阵法测量深部构造首先将微震阵法测得的S波速度与三诺钻孔PS测井测得的S波速度进行对比，验证了微震阵法的有效性。然后，在Nobi平原上总共调查了12个地点。结果表明，虽然名古屋东部基岩深度约为500 ~ 600m，但西部地区存在基岩突发性侵彻。地震运动的模拟和地面结构模型的检验在大比平原的NE-SW和NW-SE方向上形成了几个截面模型。采用二维有限元法的模拟分析较好地再现了观测波，而基于有限差分法的三维分析对由表面波组成的后相有较好的表达。

This report briefly describes about the results of survey and earthquake observation at the San-no hot spring borehole in Nagoya city, the microtremor array survey and the earthquake simulation analysis in the Nobi plain.1. Survey and earthquake observation at the San-no boreholeIt was confirmed that a base rock, consisting of hard granite ; Vs=2.8km/s, under the San-no site lied at a depth of about 670m and S wave velocity distribution was also obtained from the PS logging along the borehole. We observed many earthquake records at the base rock and surface ground, including the micro earthquakes happened under the Nobi plain.2. Survey of deep structure using the microtremor array methodAt first, the microtremor array method was verified by comparing the S wave velocities estimated from this method with those obtained by PS logging along the San-no borehole. Then, twelve sites in all were surveyed on the Nobi plain. Consequently, it was clarified that the abrupt incrimination of base rock exists beneath the western area of Nagoya city, though the base rock at eastern part is about from 500m to 600m in depth.3. Simulation of earthquake motion and examination of ground structure modelSeveral cross section models ware made up in NE-SW and NW-SE directions across the Nobi plain. The simulation analysis by using 2-D finite element method well reproduces the observational waves, and 3-D analysis based on finite difference method shows a good expression for an after phase consisted of surface waves.