Earthquake-cycle deformation at subduction zones is not only induced by cyclical faulting processes but also impacted by the Earth structure and rheology. Oversimplifying the first-order Earth structure in models leads to biased estimations of fault kinematics and Earth rheology and hence misinterpretation of subduction-zone dynamics. Here we first use synthetic models to investigate the impacts of an elastic slab on viscoelastic postseismic and interseismic deformation and on determining afterslip, locking distribution, and mantle viscosity. We confirm that the presence of a slab causes anchored viscous flow in the mantle wedge and less extensive viscoelastic deformation in the overriding plate than the depth-dependent layered models without a slab during the interseismic and postseismic phases. By assuming the predicted viscoelastic deformation from the model with a slab as the synthetic true observations, layered models obtain a higher viscosity and more slip on the downdip of the seismogenic zone than the true model during both phases. These biased estimates are found varying with the displacement component, spatial and temporal coverages of the used observations. We then conduct two real-world case studies at the Japan subduction zone and find that the layered model obtains the biased fault kinematics and mantle viscosity that are similar to the synthetic modeling results, indicating that the slab signature may have been observed in the geodetic data. Our findings highlight the importance of including a slab in modeling the earthquake-cycle deformation and thoroughly exploring the sensitivities of surface deformation, especially the verticals, on the deep Earth structures.

中文翻译：

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粘弹性地幔中的弹性板片：对确定震后和震间阶段大逆冲滑移和地幔粘度的影响

俯冲带的地震周期变形不仅是由周期性断层过程引起的，而且还受到地球结构和流变学的影响。在模型中过度简化一阶地球结构会导致对断层运动学和地球流变学的估计有偏差，从而导致对俯冲带动力学的误解。在这里，我们首先使用合成模型来研究弹性板对粘弹性震后和震间变形以及确定后滑、锁定分布和地幔粘度的影响。我们证实，在震间和震后阶段，与没有板的深度相关分层模型相比，板的存在导致地幔楔中的锚定粘性流动和覆盖板中的粘弹性变形较小。通过假设从具有板坯的模型预测的粘弹性变形作为合成真实观测值，分层模型在两个阶段都比真实模型在发震带的下倾获得更高的粘度和更多的滑移。发现这些有偏估计随所用观测的位移分量、空间和时间覆盖范围而变化。然后我们在日本俯冲带进行了两个真实世界案例研究，发现分层模型获得了与合成建模结果相似的偏断断层运动学和地幔粘度，表明在大地测量数据中可能已经观察到板片特征. 我们的研究结果强调了在模拟地震周期变形和彻底探索表面变形的敏感性中包括一块板的重要性，