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

本报告简要介绍了名古屋市山野温泉钻孔的调查和地震观测结果、野比平原的微动台阵调查和地震模拟分析。在山路钻孔中的测量和地震观测证实了山路场地下约670米深处有一个由坚硬花岗岩组成的基岩，Vs=2.8km/s，并从沿着钻孔的PS测井中获得了S波速度分布。我们在基岩和地表观测到了许多地震记录，包括在Nobi平原下发生的微震。首先，通过将由该方法估计的S波速度与由PS测井沿山路井眼沿着获得的S波速度进行比较，验证了微动阵列方法。然后，在Nobi平原上总共调查了12个地点。因此，阐明了名古屋市西部地区的基岩虽然深度在500 ~ 600 m之间，但其下方存在基岩的突然侵入.地震运动的模拟和地面结构模型的检验制作了横跨Nobi平原的NE-SW和NW-SE两个方向的几个横截面模型。二维有限元法模拟分析较好地再现了观测波，三维有限差分法模拟分析较好地再现了由面波组成的后相。

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.