We apply a geodetic slip inversion technique to analog subduction megathrust earthquakes to demonstrate how limited offshore geodetic coverage affects coseismic slip models. We analyzed two archetypical megathrust earthquakes: trench‐breaking and non‐trench‐breaking earthquakes. Slip inversion models of analog earthquakes show quantitative and qualitative changes as a function of offshore coverage. Shallow slip cannot be resolved if the observation coverage of the offshore segment is <50%. Moreover, the slip pattern of shallow event flips from landward to trenchward skewed as offshore coverage reduces to <40%. The estimated slip for both event types converges to a similar unimodal pattern when there is no offshore coverage. We infer 5‐20% slip overestimation when the observations are above the high slipping zone during trench‐breaking events versus 5‐10% underestimation during non‐trench‐breaking events if observations are land‐limited. The moment magnitude derived for trench‐breaking ruptures might be significantly affected (ΔM w ~ 0.5).

中文翻译：

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关于近海大地测量覆盖与滑动模型不确定性之间的关系：模拟超强地震案例研究

我们将大地滑动反演技术应用于模拟俯冲超逆冲地震，以展示有限的近海大地测量覆盖范围如何影响同震滑动模型。我们分析了两种典型的巨型逆冲地震：破沟地震和非破沟地震。模拟地震的滑动反演模型显示了作为离岸覆盖函数的数量和质量变化。如果近海段的观测覆盖率<50%，则无法解决浅层滑移问题。此外，随着海上覆盖率降低到 <40%，浅层事件的滑动模式从陆地向海沟倾斜。当没有离岸覆盖时，两种事件类型的估计滑移会收敛到类似的单峰模式。当在开沟事件期间观测值高于高滑移带时，我们推断滑移高估了 5-20%，而如果观测值受陆地限制，则在非开沟事件期间则低估了 5-10%。由开沟破裂导出的力矩大小可能会受到显着影响（ΔM w ~ 0.5）。