On the Choice and Implications of Rheologies That Maintain Kinematic and Dynamic Consistency Over the Entire Earthquake Cycle
On the Choice and Implications of Rheologies That Maintain Kinematic and Dynamic Consistency Over the Entire Earthquake Cycle
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DOI：
10.1029/2022jb024683
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发表时间：
2022-01
期刊：
影响因子：
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通讯作者：
Rishav Mallick;Valère Lambert;B. Meade
中科院分区：
文献类型：
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作者：
Rishav Mallick;Valère Lambert;B. Meade
上地幔中的粘弹性过程重新分布了地震产生的应力，并在整个地震周期中调制了地壳形变。对壳幔系统表面这些运动的大地观测提供了限制上地幔流变性的可能性。在地震周期的非地震阶段，粘弹性调制变形的简约表示应该同时解释以下大地测量观测：(A)震后快速变形，(B)地震周期后期的近断层应变局部化。为了了解流变公式如何影响运动学，我们比较了整个地震周期内随时间变化的正演模型对均匀弹性地壳中理想化的垂直走滑断层的预测，该地壳被均匀的粘弹性上地幔覆盖。我们探索了从实验室实验推断的三种不同的流变学：(A)线性Maxwell，(B)线性Burgers，(C)幂定律。线性Burgers模型和幂定律模型在整个地震周期内与快变形和慢变形现象一致，而单层线性Maxwell模型则不符合。线性Burgers模型和幂定律模型的运动学相似性表明，仅靠大地测量观测可能不足以区分它们，但表明一个模型可以有效地替代另一个模型。然而，幂定律流变模型显示了一种与震级非线性相关的震后响应，这可能为一些6.5-7.0级地震附近的有限震后变形观测提供了部分解释。我们讨论了摩擦滑动和粘性蠕变之间的机械耦合在控制大地震后区域应力传递的时间依赖性中的作用，以及这可能如何影响地震危险性和对居住在断层网络附近的社区的风险。
Viscoelastic processes in the upper mantle redistribute seismically generated stresses and modulate crustal deformation throughout the earthquake cycle. Geodetic observations of these motions at the surface of the crust‐mantle system offer the possibility of constraining the rheology of the upper mantle. Parsimonious representations of viscoelastically modulated deformation through the aseismic phase of the earthquake cycle should simultaneously explain geodetic observations of (a) rapid postseismic deformation, (b) late in the earthquake cycle near‐fault strain localization. To understand how rheological formulations affect kinematics, we compare predictions from time‐dependent forward models of deformation over the entire earthquake cycle for an idealized vertical strike‐slip fault in a homogeneous elastic crust underlain by a homogeneous viscoelastic upper‐mantle. We explore three different rheologies as inferred from laboratory experiments: (a) linear Maxwell, (b) linear Burgers, (c) power‐law. The linear Burgers and power‐law rheologies are consistent with fast and slow deformation phenomenology over the entire earthquake cycle, while the single‐layer linear Maxwell model is not. The kinematic similarity of linear Burgers and power‐law models suggests that geodetic observations alone may be insufficient to distinguish between them, but indicate that one may serve as an effective proxy for the other. However, the power‐law rheology model displays a postseismic response that is non‐linearly dependent on earthquake magnitude, which may offer a partial explanation for observations of limited postseismic deformation near some magnitude 6.5–7.0 earthquakes. We discuss the role of mechanical coupling between frictional slip and viscous creep in controlling the time‐dependence of regional stress transfer following large earthquakes and how this may affect the seismic hazard and risk to communities living close to fault networks.