Rheologic variations in the Earth's crust (like elastic plate thickness [EPT] or crustal rigidity) modulate the rate at which seismic moment accumulates for potentially hazardous faults of the San Andreas Fault System (SAFS). To quantify rates of seismic moment accumulation, Global Navigation Satellite Systems, and Interferometric Synthetic Aperture Radar data were used to constrain surface deformation rates of a four‐dimensional viscoelastic deformation model that incorporates rheological variations spanning a 900 km section of the SAFS. Lateral variations in EPT, estimated from surface heat flow and seismic depth to the lithosphere‐asthenosphere boundary, were converted to lateral variations in rigidity and then used to solve for seismic moment accumulation rates on 32 fault segments. We find a cluster of elevated seismic moment rates (11–20 × 10¹⁵ Nm year⁻¹ km⁻¹) along the main SAFS trace spanning the historical M_w 7.9 1857 Fort Tejon earthquake rupture length; present‐day seismic moment magnitude on these segments ranges from M_w 7.2–7.6. We also find that the average plate thickness in the Salton Trough is reduced to only 60% of the regional average, which results in a ∼60% decrease in moment accumulation rate along the Imperial fault. Likewise, a 30% increase of average plate thickness results in at least a ∼30% increase in moment rate and even larger increases are identified in regions of complex plate heterogeneity. These results emphasize the importance of considering rheological variations when estimating seismic hazard, suggesting that meaningful changes in seismic moment accumulation are revealed when considering spatial variations in crustal rheology.

中文翻译：

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San Andreas断层系统横向地壳变化的地震矩累积响应

地壳的流变学变化（如弹性板厚度[EPT]或地壳刚度）可调节圣安德烈亚斯断层系统（SAFS）潜在危险断层的地震矩累积速率。为了量化地震矩的累积速率，全球导航卫星系统和干涉合成孔径雷达数据被用来约束一个二维粘弹性变形模型的表面变形速率，该模型包含了跨越SAFS 900 km区域的流变变化。从表面热流和地震深度到岩石圈-软流圈边界的估算，EPT的横向变化被转换为刚度的横向变化，然后用于求解32个断层段的地震矩累积率。¹⁵  Nm的一年^-1公里^-1）沿主要粮食系统跟踪跨越的历史中号_W¯¯ 7.9 1857年堡特洪地震破裂长度; 这些段上的当前地震矩震级范围为M _w7.2–7.6。我们还发现，索尔顿海槽中的平均板厚仅减小到了区域平均值的60％，这导致沿帝国断层的弯矩累积率降低了约60％。同样，平均板厚增加30％会使弯矩率至少增加约30％，并且在复杂板异质性区域中甚至可以发现更大的增加。这些结果强调了在估计地震危险时考虑流变变化的重要性，表明当考虑地壳流变的空间变化时，揭示了地震矩累积的有意义的变化。