We conducted centroid moment tensor (CMT) inversions of moderate ( Mw 4.5–6.5) earthquakes in the Kanto region, Japan, using a local three-dimensional (3D) model. We then investigated the effects of our 3D CMT solutions on long-period ground motion simulations. Grid search CMT inversions were conducted using displacement seismograms for periods of 25–100 s. By comparing our 3D CMT solutions with those from the local one-dimensional (1D) catalog, we found that our 3D CMT inversion systematically provides magnitudes smaller than those in the 1D catalog. The Mw differences between 3D and 1D catalogs tend to be significant for earthquakes within the oceanic slab. By comparing ground motion simulations between 1D and 3D velocity models, we confirmed that observed Mw differences could be explained by differences in the rigidity structures around the source regions between 3D and 1D velocity models. The 3D velocity structures (especially oceanic crust and mantle) are important for estimating seismic moments in intraslab earthquakes, which are related to fault size estimation. A detailed discussion for intraslab seismicity can be conducted using the 3D CMT catalog. The seismic moments also directly affect the amplitudes of ground motions. The 3D CMT catalog allows us to directly conduct the precise forward and inverse modeling of long-period ground motion without adjusting source models, which have been typically applied in the cases using the 1D CMT catalog. We also conducted long-period ground motion simulations using our 3D CMT solutions to evaluate the reproducibility of long-period ground motions at stations within the Kanto Basin. The simulations of our 3D CMT solutions well-reproduced observed ground motions for periods longer than 10 s, even at stations within the Kanto Basin. The reproducibility of simulations was improved from those using solutions in the 1D catalog.

中文翻译：

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日本关东地区基于区域三维模型的质心矩张量反演长周期地震动模拟

我们使用局部三维 (3D) 模型对日本关东地区的中等 (Mw 4.5-6.5) 地震进行了质心矩张量 (CMT) 反演。然后，我们研究了我们的 3D CMT 解决方案对长周期地面运动模拟的影响。使用位移地震图进行网格搜索 CMT 反演，时间为 25-100 秒。通过将我们的 3D CMT 解决方案与局部一维 (1D) 目录中的解决方案进行比较，我们发现我们的 3D CMT 反演系统地提供了比一维目录中的更小的量级。3D 和 1D 目录之间的 Mw 差异对于大洋板块内的地震往往是显着的。通过比较 1D 和 3D 速度模型之间的地面运动模拟，我们证实观察到的 Mw 差异可以用 3D 和 1D 速度模型之间源区域周围的刚度结构差异来解释。3D 速度结构（尤其是海洋地壳和地幔）对于估计板内地震中的地震矩很重要，这与断层尺寸估计有关。可以使用 3D CMT 目录对板内地震活动进行详细讨论。地震矩也直接影响地震动的幅度。3D CMT 目录使我们可以直接对长周期地震动进行精确的正向和逆向建模，而无需调整源模型，这在使用 1D CMT 目录的情况下是典型的应用。我们还使用我们的 3D CMT 解决方案进行了长周期地震动模拟，以评估关东盆地内各站长周期地震动的再现性。我们的 3D CMT 解决方案的模拟很好地再现了超过 10 秒的时间段观察到的地面运动，即使在关东盆地内的站点也是如此。与使用 1D 目录中的解决方案相比，模拟的再现性得到了提高。