GREEN’S FUNCTION DATABASE AND DETAILED GROUND MOTION PREDICTION FOR CENTRAL JAPAN BASED ON THE RECIPROCITY THEOREM
GREEN’S FUNCTION DATABASE AND DETAILED GROUND MOTION PREDICTION FOR CENTRAL JAPAN BASED ON THE RECIPROCITY THEOREM
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发表时间：
2016
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通讯作者：
T. Hirai;N. Fukuwa
中科院分区：
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作者：
T. Hirai;N. Fukuwa
地面运动的详细预测在高层、隔基等关键建筑的设计中具有重要意义。一般来说，地面运动的主要周期被认为在每个地点是恒定的。然而，最近的一些研究报告说，在沉积盆地上的一些地点，观测到的地面运动的主要周期可以根据震源方向而变化。因此，对于包含上述建筑物类型的场地，应采用波形进行详细的地震动预测。由于有限差分法可以考虑沉积盆地复杂的土壤结构，故常采用有限差分法对长周期地震动波形进行预测。然而，有限差分法计算地震动需要大量的计算资源和时间。如果在一个重要地点周围假定有许多可能发生的地震，那么预测长周期地面运动是非常昂贵的。在这项研究中，我们提出了一种有效的方法来预测由许多可能的地震引起的特定地点的长周期地面运动。该方法采用基于互易定理的有限差分法计算地震动的格林函数。根据这个定理，在源处受双偶力作用的位移等于在源处受单力作用的应变。利用格林函数的互易性，可以大大降低获得格林函数完备集的计算代价。一旦在数据库中编制了代表每个单元断层在场地上的位移的格林函数，就可以很容易地通过叠加格林函数来预测由于任意机制的地震在场地上的地面运动。我们将上述方案应用于日本中部几个重要地点的地面运动预测。因此，可以有效地计算出未来几次地震所引起的地面运动。此外，我们的方案对于讨论地震动的行为和与地震机制有关的对建筑物的影响是有用的。
Detailed prediction of ground motion is important in the design of high-rise, base-isolated, and other key buildings. In general, the predominant period of ground motion is considered to be constant at each site. However, some recent studies have reported that the predominant period of observed ground motion can vary according to the source direction at sites on sedimentary basins. Therefore, detailed ground motion prediction with waveforms should be advanced for sites containing the types of buildings described above. The waveform of long-period ground motion is often predicted using the finite difference method, since the complicated soil structure of a sedimentary basin can be considered with this method. However, ground motion calculations using the finite difference method require large amounts of computational resources and time. If many possible earthquakes are assumed around an important site, it is very expensive to predict the long-period ground motion. In this study, we propose an efficient method for predicting long-period ground motions due to many possible earthquakes for a specific site. In this method, the Green’s functions of the ground motions are calculated using the finite difference method based on the reciprocity theorem. According to this theorem, the displacement at the site due to a double couple force at the source equals the strain at the source due to a single force at the site. By using the reciprocity of Green’s functions, the computational cost of obtaining a complete set of Green’s functions can be dramatically reduced. Once the Green’s functions representing the displacement at the site due to every element fault have been compiled in a database, the ground motions at the site due to earthquakes with arbitrary mechanisms can be easily predicted by superposing Green’s functions. We apply above scheme to predict ground motions at several important sites in central Japan. As a result, the ground motions at the sites due to several cases of future earthquakes can be calculated efficiently. In addition, our scheme is useful for discussing the behavior of ground motion and the impact on the buildings in relation to seismic mechanisms.