Our understanding of earthquakes is limited by our knowledge, and our description, of the physics of the Earth. When solving for subsurface fault slip, it is common practice to assume minimum complexity for the Earth's characteristics such as topography, fault geometry and elastic properties. These characteristics are difficult to include in simulations and our knowledge of them is incomplete, leading many to believe that there is minimal advantage to be gained by accounting for these effects. However, 3D structure can be easily included with the newly-developed software package SPECFEM-X, and topography and bathymetry can be measured directly and are well known all over the Earth's surface. Accounting for topography thus seems to be an efficient strategy for incorporating accurate and extensive information into the inverse problem. Here, we explore the impact of topography on static slip estimates, with a particular focus on how topography may impact slip resolution on the fault. We also wonder if the influence of topography can be accounted for by simply using a receiver elevation correction. To this end, we analyze the 2015 M w 7.5 Gorkha, Nepal, and the 2010 M w 8.8 Maule, Chile, earthquakes within a Bayesian framework. The regions affected by these events represent two different types of topography. Chile, which contains both the Peru-Chile trench and the Andes mountains, has a greater elevation range and steeper gradients than Nepal, where the primary topographic feature is the Himalayan mountain range. Additionally, the slip of the continental Nepal event is well constrained, whereas observations are less informative in a subduction context. We show that topography has a non-negligible impact on inferred slip models. Our results suggest that the effect of topography on slip estimates increases with two main factors: poor observational constraints and high elevation gradients. In particular, we find that accounting for topography improves slip resolution where topographic gradients are large and the data is less informative: at depths for the Gorkha event, and near the trench for the Maule event. When topography has a significant impact on slip resolution, which is probably the case of many subduction events, the receiver elevation correction is not sufficient.

中文翻译：

---

地形对地震静滑移估计的影响

我们对地震的理解受限于我们对地球物理学的了解和描述。在求解地下断层滑动时，通常的做法是假设地球特征（例如地形、断层几何形状和弹性特性）的复杂性最小。这些特征很难包含在模拟中，而且我们对它们的了解并不完整，因此许多人认为，考虑到这些影响，所获得的优势微乎其微。然而，新开发的软件包 SPECFEM-X 可以轻松地包含 3D 结构，并且可以直接测量地形和水深测量，并且在整个地球表面都是众所周知的。因此，考虑地形似乎是将准确和广泛的信息纳入逆问题的有效策略。这里，我们探讨了地形对静态滑动估计的影响，特别关注地形如何影响断层上的滑动分辨率。我们还想知道是否可以通过简单地使用接收器高程校正来解释地形的影响。为此，我们在贝叶斯框架内分析了 2015 年 M w 7.5 尼泊尔廓尔喀地震和 2010 M w 8.8 智利 Maule 地震。受这些事件影响的地区代表两种不同类型的地形。智利包含秘鲁-智利海沟和安第斯山脉，与尼泊尔相比，其海拔范围更大，坡度更陡，尼泊尔的主要地形特征是喜马拉雅山脉。此外，尼泊尔大陆事件的滑移受到很好的限制，而在俯冲背景下的观测信息较少。我们表明地形对推断的滑动模型具有不可忽略的影响。我们的结果表明，地形对滑动估计的影响随着两个主要因素而增加：较差的观测约束和高海拔梯度。特别是，我们发现在地形梯度较大且数据信息较少的情况下，考虑地形可以提高滑移分辨率：在廓尔喀事件的深处，以及在莫莱事件的海沟附近。当地形对滑动分辨率有显着影响时（这可能是许多俯冲事件的情况），接收器高程校正是不够的。我们发现，在地形梯度较大且数据信息较少的情况下，考虑地形可以提高滑移分辨率：在 Gorkha 事件的深处，以及在 Maule 事件的海沟附近。当地形对滑动分辨率有显着影响时（这可能是许多俯冲事件的情况），接收器高程校正是不够的。我们发现，在地形梯度较大且数据信息较少的情况下，考虑地形可以提高滑移分辨率：在 Gorkha 事件的深处，以及在 Maule 事件的海沟附近。当地形对滑动分辨率有显着影响时（这可能是许多俯冲事件的情况），接收器高程校正是不够的。