Seismic velocity discontinuities beneath the Japan Islands with receuver function tomography

研究了接收函数层析成像方法，该方法可以同时确定三维地震速度结构和速度不连续面。通过研究，我们认识到开发raid的必要性以及在包含速度不连续面的三维速度结构中合成波形的有效方法，并在此基础上开发了一种基于改进高斯波束法（GBM）的raid波形合成方法。我们将这种方法应用于在日本西南部的纪伊半岛观测到的波形，在那里菲律宾海板块以复杂的三维结构俯冲。我们综合了径向、横向和垂直的射频波，并将其与观测的射频波进行比较，研究了菲律宾海板块下降的顶部结构和海洋莫霍线。作为结果,我们证实了阶段出现在观察到的径向和横向RFs P S波转换(Ps)阶段的地震速度不连续,相对于和阶段在垂直RFs P波反射面和倾斜速度不连续(PpdP)。此外，我们还利用Hi-net倾斜仪产生的RFs对俯冲太平洋板块的顶部、海洋板块和底部进行了研究。特别是在站密度高的日本中部地区，径向和横向rf分析显示脱水水被输送。进入地幔过渡带。的;RF分析显示的低速带表明存在脱水水层。最后，我们基于速率和状态依赖的摩擦对流体浸润板界面上的地震周期进行了二维模拟，并研究了粪便深度与深度孔隙压力分布的关系。

We investigated the method of receiver function (RF) tomography by which we simultaneously determine the smoothly varying 3-D seismic velocity structure and the velocity discontinuity surfaces. Through the investigation, we recognized the necessity of developing the raid and efficient method of synthesizing waveforms in a 3-D velocity structure including velocity discontinuities, and then developed a raid waveform synthetic method based on improved Gaussian Beam method (GBM). We applied this method to the waveforms observed in the Kii peninsula, southwest Japan, where the Philippine Sea plate is subducting with a complex 3-D configuration. We synthesized radial, transverse and vertical RFs, and compared them with the observed ones to investigate the structure of the top and the oceanic Moho of the descending Philippine Sea slab. As results, we confirmed the phases appeared in the observed radial and transverse RFs are the P to S wave converted (Ps) phases at the inclined seismic velocity discontinuities, and the phases in the vertical RFs are the P waves reflected at the surface and the inclined velocity discontinuities (PpdP).Further, we investigated the top, the oceanic Moth and the bottom of the subducting Pacific slab by employing the RFs produced from Hi-net tiltmeters. Especially in the central Japan region where the station density is high, the analyses using bath the radial and transverse RFs revealed that dehydrated water is transported. into the mantle transition zone.The ; low velocity zone revealed by RF analyses indicates the existence of the layer of dehydrated water. Finally, we executed 2-D simulation of earthquake cycle on a fluid-infiltrated plate interface based on a rate and state dependent friction, and investigated the relation between the fecal depth and the pore pressure distribution at depths.