Rapid tremor reversals in Cascadia generated by a weakened plate interface
Rapid tremor reversals in Cascadia generated by a weakened plate interface
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DOI：
10.1038/ngeo1157
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发表时间：
2011-06-01
影响因子：
18.3
通讯作者：
Creager, Kenneth C.
中科院分区：
文献类型：
--
作者：
Houston, Heidi;Delbridge, Brent G.;Creager, Kenneth C.
在俯冲带沿板块界面的缓慢滑动沿着可以在一个称为幕式震颤和滑动的准周期过程中产生微弱的地震震颤。这一过程与常规地震破裂的特征不同，可以释放在深部板块界面上积聚的应力。在这里，我们分析了2004年至2009年在北方华盛顿的卡斯卡迪亚俯冲带的五个最大的幕式地震和滑动事件的时空演变。我们发现，这些事件是相似的，但不是完全相同的，因为它们在不同的位置启动，并沿着沿着板块界面以不同的平均速度传播，每天7至12公里。我们的分析表明，地震可以迅速迁移回来，远离地震和滑动正在推进的区域，通过过去三天刚刚破裂的板块界面部分。这些快速的震颤反向传播数十公里的速度比相对缓慢，稳定的间歇性震颤和滑动的速度快20至40倍。我们的观察结果表明，一旦板块界面被削弱的初始推进幕式震颤和滑动，它允许应力更容易地诱导滑动或流体压力波迁移回来更快，产生快速的震颤逆转。
Slow slip along the plate interface at subduction zones can generate weak seismic tremor in a quasi-periodic process called episodic tremor and slip. This process differs in character from regular earthquake rupture and can release stresses that build up on the deep plate interface. Here we analyse the spatial and temporal evolution of the five largest episodic tremor and slip events between 2004 and 2009 in northern Washington on the Cascadia subduction zone. We find that the events are similar, but not identical because they initiate in different locations and propagate along the plate interface at different average speeds of 7 to 12 km per day. Our analysis reveals that tremor can migrate rapidly back, away from the region where tremor and slip are advancing, through parts of the plate interface that have just ruptured in the past three days. These rapid tremor reversals propagate backwards for tens of kilometres at speeds that are 20 to 40 times faster than the relatively slow, steady advance of episodic tremor and slip. Our observations suggest that once the plate interface is weakened by the initial advance of episodic tremor and slip, it allows stresses to induce slip more easily or fluid pressure waves to migrate back more rapidly, generating rapid tremor reversals.