Fault source models inverted from surface displacement measurements are a common tool to contextualize the seismotectonic significance of earthquakes. However, these models commonly invoke a simplified homogeneous elastic half‐space (flat Earth) description of Earth, which may bias the resulting fault geometries and slip distributions in the presence of spatially varying Earth's elastic structure and topography. Here, we developed both forward and inverse three‐dimensional finite‐element models with planar faults to systematically assess the impacts of topography, crustal elastic structure, and fault geometry on surface deformation and earthquake source inversions, with a focus on the 2015 Gorkha, Nepal earthquake. Our forward models with fixed fault slip confirm the impacts of topography and crustal heterogeneity on surface deformation. These impacts, however, contribute only maximally ∼10% of the total surface displacement, and the fault depth and dip dominantly control the coseismic deformation for the Gorkha case. When using homogeneous half‐space models to invert the synthetic displacement fields generated by forward finite‐element models, we find that ignoring crustal heterogeneity primarily biases inferred dip angle, while ignoring relief primarily biases inferred fault depth. Our inversions based on finite‐element models suggest that topography and crustal heterogeneity introduce negligible bias on recovering the Gorkha line of sight observations. Fault dip angle and depth can systematically trade off with slip area and slip magnitude, regardless of the presence of relief and crustal heterogeneities. Taken together, our findings highlight the importance of fault geometry on inverted fault kinematics with geodetic observations in the central Himalayan arc.

中文翻译：

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地形起伏和地壳异质性对断层几何形状和滑移的同震形变和反演的影响：以2015年喜马拉雅中部弧线的Gorkha地震为例

从地表位移测量反演的断层震源模型是将地震的地震构造意义与背景联系起来的常用工具。但是，这些模型通常会调用简化的地球均质弹性半空间（平坦地球）描述，在存在空间变化的地球弹性结构和地形的情况下，这可能会导致最终的断层几何形状和滑动分布发生偏差。在这里，我们开发了带有平面断层的正向和反向三维有限元模型，以系统地评估地形，地壳弹性结构和断层几何形状对地表变形和地震震源反演的影响，重点是2015年尼泊尔的戈尔卡地震。我们具有固定断层滑动的正向模型证实了地形和地壳非均质性对表面变形的影响。然而，这些影响最多仅占总表面位移的约10％，而断层深度和倾角主要控制了戈尔卡案例的同震变形。当使用齐次半空间模型对由正向有限元模型生成的合成位移场进行反演时，我们发现忽略地壳非均质性首先会推论出倾角，而忽略起伏则主要会推论出断层深度。我们基于有限元模型的反演表明，地形和地壳异质性在恢复戈尔卡视线观测值时引入了可忽略的偏差。断层倾角和深度可以与滑动面积和滑动幅度系统地权衡，而与起伏和地壳非均质性无关。在一起