We propose an optimization method for applying the seismic‐wave gradiometry (SWG) method to a dense seismic station network consisting of nonuniformly distributed seismographs. As a nonuniformly distributed station array, we consider the station layout of the Metropolitan Seismic Observation Network (MeSO‐net) operated in and around the Tokyo metropolitan area, Japan. In this study, thereby, we numerically investigate optimum shapes of weighting functions, which control the spatial weights of individual stations when estimating waveforms at any grid points in the SWG method, to reconstruct seismic wavefields propagating in the MeSO‐net. The functions with isotropic spatial weights are found to be appropriate for wavefield reconstructions with seismic waves incoming from practically all directions, even for nonuniformly distributed stations. The reproducibility of the wavefields is greatly improved by changing the shapes of the spatial weights reflecting density of the stations. Further plausible wavefield reconstructions are made by considering the propagation directions of the seismic waves. In these cases, if the weight of a contribution for a wavefield reconstruction is larger at far stations with a direction perpendicular to the wave propagation direction, then the reproducibility of the waveforms is significantly increased. In addition, the spatial gradients of the amplitudes are well reproduced by the optimized SWG method even though the optimization only focused on the amplitudes. Therefore, our proposed optimization scheme can be used to accurately estimate seismic wavefields in a nonuniformly distributed station array. Actually, the weighting functions optimized in this study succeeded to reconstruct the seismic wavefield of a shallow crustal earthquake that occurred around the Tokyo metropolitan area, based on the observed seismograms obtained by the MeSO‐net.

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密集和非均匀分布台站的最佳二维地震波波场重构：日本大都市地震观测网

我们提出了一种将地震波梯度法（SWG）应用于由非均匀分布的地震仪组成的密集地震台网的优化方法。作为非均匀分布的台站阵列，我们考虑在日本东京都会区及其周围地区运营的大都市地震观测网（MeSO-net）的站台布局。因此，在本研究中，我们以数字方式研究了加权函数的最佳形状，这些加权函数可在SWG方法中估计任何网格点处的波形时控制各个站点的空间权重，以重建在MeSO网络中传播的地震波场。发现具有各向同性空间权重的函数适用于从几乎所有方向入射的地震波的波场重建，即使对于分布不均匀的站也是如此。通过更改反映站点密度的空间权重的形状，可以大大提高波场的可重复性。通过考虑地震波的传播方向，可以进行进一步的波场重构。在这些情况下，如果在垂直于波传播方向的远距离站中，对波场重构的贡献权重更大，则波形的可重复性将显着提高。此外，即使优化仅集中在振幅上，通过优化的SWG方法也可以很好地再现振幅的空间梯度。因此，我们提出的优化方案可用于精确估计非均匀分布台站阵列中的地震波场。实际上，