The major physiographic “smooth plains” units on Mercury are dominantly composed of volcanic deposits that have been deformed by horizontal compressive stresses. An open issue is whether these features formed by stresses induced by global contraction, bending stresses due to volcanic loading, or some combination of both. In this study, we model the surface expression of 12 shortening structures within several smooth plains units across Mercury to determine the geometries of the underlying faults. We implement an elastic dislocation model, using both listric and planar fault geometries, to place estimates on the depth of faulting for each feature. We show that a majority of smooth plains shortening structures penetrate the lithosphere to depths greater than 15 km. Thrust faults of this scale have not previously been recognized within the planet's smooth plains units and require a large horizontal stresses to form, which is best explained if this stress arises from global contraction. Further, our results suggest that the observed relief and length contrast between features in the smooth plains units and older intercrater plains units can be explained by interior layering of, and/or a shallower brittle‐ductile transition underlying, the smooth plains units.

中文翻译：

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汞光滑平原内的断裂构造和压缩构造特征成因

水星上主要的自然“光滑平原”单元主要由火山沉积物组成，这些火山沉积物已因水平压缩应力而变形。一个开放的问题是这些特征是由整体收缩引起的应力，由于火山载荷引起的弯曲应力还是两者的某种组合形成的。在这项研究中，我们对横跨水星的几个平滑平原单元内的12个缩短结构的表面表达进行建模，以确定潜在断层的几何形状。我们使用弹塑性断层和平面断层的几何形状来实现弹性错位模型，以便对每个特征的断层深度进行估算。我们表明，大多数光滑的平原缩短结构穿透岩石圈的深度大于15 km。这种规模的逆冲断层以前尚未在行星的内部被发现。是光滑的平原单元，需要较大的水平应力才能形成，如果这种应力是由整体收缩引起的，则可以最好地解释。此外，我们的结果表明，可以用光滑平原单元的内部分层和/或下面的较浅脆性-延性转变来解释光滑平原单元和较早的火山口平原单元中的特征之间观察到的浮雕和长度对比。