Development of statistical strong-motion evaluation method based on regional variation of source and path effects in the Tohoku region, Japan

为了更精确地估计地震危险性图，我们开发了一种统计（经验）评估方法的强震谱考虑区域变化的源，路径和网站的影响，在日本东北地区。主要研究结果如下：1.利用DPRI K-NET、KiK-NET、PARI、JMA Type-87和Type-95强震台网资料，编制了东北地区强震数据库.我们对同一数据集的S波傅立叶谱和反应谱进行了谱反演分析，并获得了每个地震的震源谱，传播路径（内陆和俯冲带，不同）的Q值，以及每个站点的站点放大因子。通过绘制布吕纳应力降图和频率相关场地放大图，发现如下趋势：（1）高频源辐射强度在宫城县以东地区很高。（2）位于火山附近的浅源内陆地震，其高频辐射强度较低。另一个地区的内陆地震具有类似于俯冲带发生的浅源地震的应力降。（3）日本海一侧0.2Hz附近的场地放大因子较大，可能是由于奥胡山以西的盆地深度比东部深。但是，在对低层建筑物的震害非常重要的0.5- 2 Hz范围内，不仅在奥胡山脉西部，而且在东部地区，如仙台平原，放大率都很大.基于谱反演结果，通过模拟地震项与矩震级和应力降的关系，以及场地放大系数与地表至30 m深度的平均横波速度Vs_（30）的关系，分析了PGA、PGV、反应谱的衰减关系。加入应力降参数后，地震项的方差大大减小。

Toward more precise estimation of earthquake hazard maps, we developed a statistical (empirical) evaluation method of strong motion spectra considering regional variation of source, path, and site effects in the Tohoku region, Japan. The main results are as follows.1. We compiled strong-motion database over the Tohoku region from DPRI K-NET, KiK-net, PARI, JMA type-87 and type-95 strong-motion network data.2. We conducted spectral inversion analyses for both S-wave Fourier and response spectra for the identical dataset, and obtained source spectrum of each earthquake, Q-value of propagating path (inland and subduction zones, differently), and site amplification factor at each site. By drawing maps of the Brune's stress drop and frequency-dependent site amplifications, the followings tendencies are found :(1)high-frequency source radiation strength is very high at east of Miyagi prefecture area.(2)shallow inland earthquakes located near volcanoes show lower high frequency radiation strength. Inland earthquakes at the other area have stress drops similar to the shallow earthquakes occurred in subduction zones.(3)site amplification factors around 0.2Hz are large at Japan-Sea side, probably due to the basin depth of west of Ohu mountains are deeper than the east area. Still, amplifications around 0.5-2Hz, which is very important ranges for the earthquake damage for low-rise building, are large not only in the west of Ohu mountains but in the east area, such as Sendai plain.3. Based on the results of spectral inversion, we evaluated attenuation relations of PGA, PGV, response spectrum by modeling earthquake term as a function of moment magnitude and stress drop, and also modeled site amplification factor as a function of Vs30, averaged S-wave velocity from the ground surface to 30m-deep. The variance of earthquake term is largely decreased by adding stress drop as a parameter.