Observations of ∼7 years of postseismic deformation following the 2012 M _w 7.8 Haida Gwaii and 2013 M _w 7.5 Craig earthquakes in western British Columbia and southeastern Alaska provides insight into the regional rheologic structure and seismological hazards. A stress‐driven afterslip‐only model cannot alone explain rates or spatial patterns of the far field and later stage postseismic deformation measured by Global Positioning System (GPS). We thus develop an integrated model that fits the observations by combining afterslip on the deeper extension of the faults and distributed viscous flow in the asthenosphere. The best‐fit integrated model has a 60‐km thick lithosphere overlying a Burgers body asthenosphere with a Maxwell viscosity of 2 × 10¹⁹ Pa s (0.8–3 × 10¹⁹ Pa s at 95% confidence), with a Kelvin viscosity assumed equal to 10% of that value. These values are in good agreement with rheological models derived from glacial isostatic adjustment data. The early, near‐field postseismic deformation from both events is dominated by their corresponding afterslip, however, throughout the Craig postseismic period, the dominant mechanism in the far field is viscoelastic relaxation. For the intermediate region between the two earthquakes, both events contribute to the observed postseismic displacements. Because there was no obvious afterslip following the Haida Gwaii event or known large historical earthquakes on the southernmost part of the QCF, this region continues to have great potential to suffer a large earthquake in the future.

中文翻译：

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2012年海达瓜7.8级地震和2013年克雷格7.5级地震引起的震后变形及其对区域流变结构的影响

继2012年~7震后变形观测中号 _W¯¯ 7.8夏洛特皇后群岛和2013年中号 _{w ^}西部不列颠哥伦比亚省的7.5克雷格地震和阿拉斯加东南部提供洞察区域流变结构和地震灾害。应力驱动的仅滑后模型不能单独解释由全球定位系统（GPS）测量的远场和后期地震后变形的速率或空间模式。因此，我们通过结合断层深处的后滑动和软流圈中的粘性流分布，开发了一个适合观测的综合模型。最佳拟合集成模型的岩石圈上有一个60 km厚的岩石圈，其麦克斯韦粘度为2×10 ¹⁹ Pa s（ 在95％置信度下为0.8–3×10 ¹⁹ Pa s），开尔文粘度假定等于该值的10％。这些值与从冰川等静压调整数据得出的流变模型非常吻合。这两个事件的早期，近场后震变形主要由其相应的后滑引起，但是，在整个克雷格地震后时期，远场的主导机制是粘弹性松弛。对于两次地震之间的中间区域，这两个事件均导致观测到的地震后位移。由于在海达瓜事件或QCF最南端的已知大历史地震之后没有出现明显的余波，因此该地区未来仍有很大的潜力遭受大地震。