Surface wave analysis of 3D seismic velocity structure using dense seismographic network

提出了一种膜表面波合成方法。该方法的主要特点是：（1）在将位移分解为垂向变化项的前提下，通过求解二维势函数，可以评价三维非均匀性对波形的影响（局部本征函数）和水平变化项（水平势函数），（2）非均匀表面波相速度分布的二维势函数的数值（直接）计算，（3）计算三维层析核函数（偏导数）的能力。计算的电位和层析核显示显着的扭曲（弯曲的路径和不对称的图案），特别是在短周期约10 s的模型structure.The膜表面波合成的瑞利波从一个例子事件（2002年关房总半岛）地震假设的横向非均匀模型显示出更强烈的频散效应比合成的一个平坦的层状模型没有。我们发现，这种分散的功能类似于所观察到的波形的特点，虽然目前的结构模型仍然不足以完全预测的观察。我们认为沉积层的重要性，特别是爱波。

We developed a membrane surface wave synthetic method. Its main features are (1) the effect of the 3D heterogeneity on the waveform may be evaluated by solving 2D potential function under the ansatz of the separation of the displacement into term of vertical variation (local eigenfunction) and term of horizontal variation (horizontal potential function), (2) numerical (direct) evaluation of the 2D potential functions for heterogeneous surface wave phase velocity distribution without asymptotic approximations, and (3) capability in evaluating the 3D tomographic kernels (partial derivatives).We made a preliminary, laterally heterogeneous model for the structure in and around Japanese Islands. The computed potentials and tomographic kernels indicate significant distortions (curved path and asymmetric pattern), especially at short periods around 10s for the model structure.The membrane surface wave synthetic for Rayleigh waves from an example event (2002 Off Boso Peninsula) earthquake assuming the laterally heterogeneous model shows more intense dispersion effect than the synthetic for a flat layered model does. We find that this dispersive feature resembles the characteristics in the observed wave forms, although the current structural model is still not sufficient in fully predicting the observation. We suggest the importance of the sedimentary layer especially for Love waves.