Permanent deformation caused by subduction earthquakes in northern Chile
Permanent deformation caused by subduction earthquakes in northern Chile
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DOI：
10.1038/ngeo1789
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发表时间：
2013-06-01
影响因子：
18.3
通讯作者：
Rech, J. A.
中科院分区：
文献类型：
--
作者：
Baker, A.;Allmendinger, R. W.;Rech, J. A.
地震伴随着同震和震后的反弹：断层两侧的地壳块体弹回到它们最初的、未变形的构造。全球定位系统等空间大地测量数据充分记录了这种反弹。因此，所有地震引起的地壳变形都被认为是非永久性的，并被模拟为弹性或粘弹性过程。然而，在这里，我们表明，智利北方7级以上的地震导致地壳永久变形。我们确定毫米到米级的张力裂缝在阿塔卡马沙漠的地壳，并使用宇宙成因核素的日期裂缝形成的时间。这些裂缝是由过去80万至100万年间发生的2,000至9,000次板块边界地震形成的。我们表明，高达10%的水平变形产生的地震，记录的全球定位系统数据和以前假设是可恢复的，是永久性的。我们的数据集提供了南美板块浅地壳永久应变的记录。虽然地壳深部的变形可能主要是弹性的，我们的结论是，地震周期的建模也应该包括一个重要的塑性成分。
Earthquakes are accompanied by coseismic and post-seismic rebound: blocks of crust on either side of the fault spring back to their initial, undeformed configuration. This rebound is well documented by space geodetic data, such as the Global Positioning System. Thus, all earthquake-induced deformation of the crust is considered non-permanent and is modelled as an elastic or visco-elastic process. Here, however, we show that earthquakes larger than magnitude 7 in northern Chile caused the crust to deform permanently. We identify millimetre-to metre-scale tension cracks in the crust of the Atacama Desert and use cosmogenic nuclides to date the timing of crack formation. The cracks were formed by between 2,000 and 9,000 individual plate-boundary earthquakes that occurred in the past 0.8-1 million years. We show that up to 10% of the horizontal deformation generated during the earthquakes, recorded by Global Positioning System data and previously assumed to be recoverable, is permanent. Our data set provides a record of permanent strain in the shallow crust of the South American Plate. Although deformation of the deep crust may be predominantly elastic, we conclude that modelling of the earthquake cycle should also include a significant plastic component.