Earthquake clustering can be promoted by local, regional, and remote triggering. The interaction between faults by static and dynamic stress transfer has received much attention. However, the role of quasi-static stress interaction mediated by viscoelastic flow is still poorly understood. Here, we investigate whether the tight synchronization of moment-magnitude 6 earthquakes every about 6 years on distant asperities in the Gofar-Discovery fault system of the East Pacific Rise may be caused by mechanical coupling within the lithosphere-asthenosphere system. We build a three-dimensional numerical model of seismic cycles in the framework of rate- and state-dependent friction with a brittle layer overlaying a viscoelastic mantle with nonlinear rheology to simulate earthquake cycles on separate asperities. The brittle section of the West Gofar fault consists of two frictionally unstable 20 km-long by 5 km-wide asperities separated by a velocity-strengthening barrier, consistent with seismic observations, allowing stress transfer by afterslip and viscoelastic relaxation. We find that viscoelastic stress transfer can promote the synchronization of earthquakes. Even if the asperities are separated by as far as 30 km, synchronization is still possible for a viscosity of the underlying mantle of 10¹⁷ Pa s, which can be attained by dislocation creep or transient creep during the postseismic period. Considering the similarities in tectonic and structural settings, viscoelastic stress transfer and earthquake synchronization may also occur at 15’20 (Mid-Atlantic Ridge), George V (Southeast Indian Ridge), Menard and Heezen transform fault (Pacific-Antarctic Ridge).

中文翻译：

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粘弹性应力对大洋转换断层地震周期同步的贡献

地震聚类可以通过本地、区域和远程触发来促进。断层间通过静态和动态应力传递的相互作用受到了广泛关注。然而，由粘弹性流动介导的准静态应力相互作用的作用仍然知之甚少。在这里，我们研究了东太平洋海隆 Gofar-Discovery 断层系统中每 6 年左右的 6 级矩震级地震在遥远的凹凸体上的紧密同步是否可能是由岩石圈-软流圈系统内的机械耦合引起的。我们在速率和状态相关摩擦的框架内建立了地震循环的三维数值模型，其中脆性层覆盖具有非线性流变学的粘弹性地幔，以模拟不同粗糙体上的地震循环。West Gofar 断层的脆性部分由两个摩擦不稳定的 20 公里长 x 5 公里宽的凹凸体组成，由速度强化屏障隔开，这与地震观测一致，允许通过后滑和粘弹性松弛进行应力传递。我们发现粘弹性应力传递可以促进地震的同步。即使凹凸体相距 30 公里，对于 10 的下伏地幔粘度仍然可以同步¹⁷  Pa s，可通过震后位错蠕变或瞬态蠕变达到。考虑到构造和构造设置的相似性，粘弹性应力传递和地震同步也可能发生在 15'20（大西洋中脊）、乔治五世（东南印度洋脊）、梅纳德和希岑转换断层（太平洋-南极海脊）。