The 2011 Tohoku-oki earthquake produced the most well-recorded postseismic deformation of any megathrust earthquake in the world. Over the last decade, researchers have used a dense and widespread geodetic network of more than 1300 Global Navigation Satellite System (GNSS) stations inland, as well as the about 50 stations on the seafloor, to investigate the various deformation sources responsible for the observed crustal deformation. One of the contributing mechanisms to this crustal deformation is the stress relaxation of the viscoelastic mantle beneath the Japanese arc. As evident in experimental rock physics and geophysical observations, ambient mantle conditions and related rheology are expected to be heterogeneous in space. However, the contribution of such rheological heterogeneities to the postseismic deformation is still poorly understood. Here, we piece together several rheological heterogeneities inferred from the decade-long postseismic deformation of the 2011 Tohoku-oki earthquake. We reviewed more than twenty postseismic models to understand how viscoelastic earth can influence the postseismic surface deformation observed after the Tohoku-oki earthquake. Besides, we employed several synthetic models to tease out the contribution of individual rheological heterogeneities such as depth-dependent rheology of mantle wedge, oceanic asthenosphere, and low-viscosity zone beneath the volcanic front. We demonstrate that the vertical postseismic observation is the key to unravel rheological complexity beneath northeastern Japan. The broader vertical deformation pattern reveals the major viscosity contrast between backarc and forearc, and small-scale subsidence detects the presence of low-viscosity bodies related to arc magmatism. In short, this review paper provides a vista of three-dimensional heterogeneous rheology of viscoelastic earth. These rheological heterogeneities may play a crucial role in bridging the gap between our understanding of different phase of subduction zone earthquake cycle.

2011 年的 Tohoku-oki 地震产生了世界上所有巨型地震中记录最完好的震后变形。在过去十年中，研究人员利用由 1300 多个内陆全球导航卫星系统 (GNSS) 站以及海底约 50 个站组成的密集而广泛的大地测量网络，调查造成所观测到的地壳的各种变形源形变。这种地壳变形的促成机制之一是日本弧下粘弹性地幔的应力松弛。正如实验岩石物理学和地球物理观测所证明的那样，环境地幔条件和相关的流变学预计在空间中是不均匀的。然而，人们对这种流变学非均质性对震后变形的影响知之甚少。在这里，我们拼凑了从 2011 年 Tohoku-oki 地震长达十年的震后变形中推断出的几种流变学异质性。我们回顾了 20 多个震后模型，以了解粘弹性地球如何影响东北冲地震后观测到的震后地表变形。此外，我们采用了几种合成模型来梳理出个别流变学非均质性的贡献，例如地幔楔、海洋软流圈和火山前缘下方的低粘度带的深度流变学。我们证明垂直震后观测是揭示日本东北部地下流变学复杂性的关键。更广泛的垂直变形模式揭示了弧后和弧前之间的主要粘度对比，小规模沉降检测到与弧形岩浆作用有关的低粘度体的存在。简而言之，这篇评论文章提供了粘弹性土的三维非均匀流变学的前景。这些流变学的不均匀性可能在弥合我们对俯冲带地震周期不同阶段的理解之间的差距方面发挥关键作用。