Buoyancy anomalies within Earth’s mantle create large convective currents that are thought to control the evolution of the lithosphere. While tectonic plate motions provide evidence for this relation, the mechanism by which mantle processes influence near-surface tectonics remains elusive. Here, we present an azimuthal anisotropy model for the Pacific Northwest crust that strongly correlates with high-velocity structures in the underlying mantle but shows no association with the regional mantle flow field. We suggest that the crustal anisotropy is decoupled from horizontal basal tractions and, instead, created by upper mantle vertical loading, which generates pressure gradients that drive channelized flow in the mid-lower crust. We then demonstrate the interplay between mantle heterogeneities and lithosphere dynamics by predicting the viscous crustal flow that is driven by local buoyancy sources within the upper mantle. Our findings reveal how mantle vertical load distribution can actively control crustal deformation on a scale of several hundred kilometers.

地幔内的浮力异常会产生巨大的对流，人们认为这些对流控制着岩石圈的演化。虽然构造板块运动为这种关系提供了证据，但地幔过程影响近地表构造的机制仍然难以捉摸。在这里，我们提出了太平洋西北地壳的方位各向异性模型，该模型与下伏地幔中的高速结构密切相关，但与区域地幔流场没有关联。我们认为，地壳各向异性与水平基底牵引力脱钩，而是由上地幔垂直载荷产生，产生驱动中下地壳通道化流的压力梯度。然后，我们通过预测上地幔内局部浮力源驱动的粘性地壳流来证明地幔异质性和岩石圈动力学之间的相互作用。我们的研究结果揭示了地幔垂直载荷分布如何主动控制数百公里范围内的地壳变形。