The Role of Slow Slip Events in the Cascadia Subduction Zone Earthquake Cycle
The Role of Slow Slip Events in the Cascadia Subduction Zone Earthquake Cycle
复制标题
慢滑移事件在卡斯卡迪亚俯冲带地震周期中的作用
DOI：
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发表时间：
2022
期刊：
影响因子：
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通讯作者：
J. Loveless
中科院分区：
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作者：
Juliette P. Saux;Elias G. Molitors Bergman;E. L. Evans;J. Loveless
在30-50 km深度的卡斯卡迪亚俯冲带界面上检测到的慢滑动事件（SSE）意味着累积应变的释放。然而，在卡斯卡迪亚的震间变形研究通常发现耦合上30公里的接口，这是公认的定义孕震区。使用净震间速度（包括SSE效应）和限制耦合到浅界面的耦合估计可能会低估深度>30 km处的滑动亏损累积。在这里，我们检测反转GPS运动的迹象SSE，然后使用SSE位移估计从2007年到2021年的累积慢滑。我们计算纯地震间的速度，纠正SSE位移，并用它们来约束弹性块模型，估计俯冲界面上的滑动赤字下降到50公里。通过独立评估滑动亏损和缓慢滑动，我们研究了SSE对地震间应变积累的影响，以及SSE间滑动亏损和缓慢滑动对前弧垂直变形的影响。我们发现，中度到高度耦合延伸到40公里的深度，而浅耦合是与以前的估计的孕震区，更深的区域的滑动赤字下面的奥林匹克半岛可能会部分（61%）缓解抗震SSE。地表隆起的模式表明，几十年来深部耦合的完全缓解可能是通过随时间变化的地震滑动速率来实现的。
Slow slip events (SSEs) detected on the Cascadia Subduction Zone interface at 30–50 km depth imply a release of accumulated strain. However, studies of interseismic deformation in Cascadia typically find coupling on the upper 30 km of the interface, which is generally accepted as defining the seismogenic zone. Estimates of coupling using net interseismic velocities (including SSE effects) and restricting coupling to the shallow interface may underestimate slip deficit accumulation at depths >30 km. Here, we detect reversals in GPS motion as indications of SSEs, then use SSE displacements to estimate cumulative slow slip from 2007 to 2021. We calculate pure interseismic velocities, correcting for SSE displacements, and use them to constrain an elastic block model, estimating slip deficit on the subduction interface down to 50 km. By evaluating slip deficit and slow slip independently, we examine SSEs’ effect on interseismic strain accumulation, and the effect of inter‐SSE slip deficit and slow slip on vertical deformation of the forearc. We find that moderate to high coupling extends to 40 km depth, and while shallow coupling is consistent with previous estimates of the seismogenic zone, a deeper region of slip deficit beneath the Olympic Peninsula may be partially (61%) relieved aseismically by SSEs. Patterns of surface uplift suggest that complete relief of deep coupling over multiple decades may be accomplished by time‐varying rates of aseismic slip.