Interplate coupling and transient slip along the subduction interface beneath Oaxaca, Mexico
Interplate coupling and transient slip along the subduction interface beneath Oaxaca, Mexico
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墨西哥瓦哈卡下方俯冲界面的板间耦合和瞬态滑移
DOI：
10.1111/j.1365-246x.2008.03910.x
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发表时间：
2008
影响因子：
2.8
通讯作者：
O. Diaz
中科院分区：
文献类型：
--
作者：
F. Correa;C. Demets;E. Cabral;B. Márquez;O. Diaz
摘要我们描述并模拟了墨西哥俯冲带瓦哈卡段的地表形变测量，以表征该地区的震间应变累积和幕式瞬时滑动，并检验基于地震学的应变沿俯冲界面累积和释放的模型。2001年至2007年在我们密集的31站GPS阵列内测量的变形包括：(1)海沟正常的水平收缩速度从海岸单调下降，(2)沿海快速下沉，在内陆100公里以上的位置逐渐改变为缓慢隆起，以及(3)中断原本稳定的变形的瞬时滑移。对2004年和2006年瞬变台站偏移量的反模拟表明，沿俯冲界面的瞬变滑动发生在2004年和2006年该地区以往大地震的破裂极限之外。在沿海岸线和内陆仅数十公里的距离上，经过这种瞬时滑动影响校正的GPS站点速度差异很大，这意味着在俯冲界面上的锁定程度也发生了类似的空间变化。在1978年7.8级浅层逆冲地震中，沿海岸测得的形变速率在破裂带核心以上达到最大值，一般向外向破裂带边缘递减。用模拟研究区的有限元网格对震间GPS速度场进行有界值的反演模拟表明，1978年浅推覆地震的大部分破裂带完全锁定在板块收敛速度上，但该地区被俯冲界面的弱锁定区域所包围，这可能会减缓或阻止未来地震的传播。从孕震带向下倾斜的更深的瞬变滑动区域的大部分也在瞬变滑动事件之间被完全锁定；然而，由于在2002至2006年间锁定这一更深的过渡带而积累的弹性能量似乎主要或完全由2004年至2006年初的瞬变滑动事件释放。瞬变滑动深部的能量收支基本平衡，这意味着该地区不太可能为未来发源于孕震带的地震贡献大量的弹性能量。我们的结果支持一个模型，在该模型中，地震凹凸区与地震之间的强锁定区域重合。自1978年以来在孕震带重新积累的潜在弹性能量已经足以导致1978年地震的重演。
SUMMARY We describe and model GPS measurements of surface deformation from the Oaxaca segment of the Mexican subduction zone to characterize interseismic strain accumulation and episodic transient slip in this region and test seismologically-based models of strain accumulation and release along subduction interfaces. Deformation measured from 2001 to 2007 within our dense 31-station GPS array has consisted of (1) trench-normal horizontal contraction at rates that decrease monotonically inland from the coast, (2) rapid coastal subsidence that changes gradually to slow uplift at locations more than 100 km inland and (3) periods of transient slip that interrupt the otherwise steady deformation. Inverse modelling of transient station offsets in 2004 and 2006 indicates that transient slip along the subduction interface occurred downdip from the rupture limits of previous large earthquakes in this region in both 2004 and 2006. GPS site velocities that are corrected for the effects of this transient slip vary significantly over distances of only tens of kilometres both along the coastline and inland, implying that similar spatial variations occur in the degree of locking across the subduction interface. Deformation rates measured along the coast reach their maximum above the core of the rupture zone of the 1978 Ms = 7.8 shallow-thrust earthquake and generally decrease outwards towards the edges of the rupture zone. Bounded-value, inverse modelling of the interseismic GPS velocity field with a finite element mesh that simulates the study region indicates that much of the rupture zone of the 1978 shallow-thrust earthquake is fully locked at the plate convergence rate, but that this region is surrounded by weakly locked areas of the subduction interface, which may slow or arrest the propagation of future earthquakes. Much of the deeper region of transient slip, downdip from the seismogenic zone, is also fully locked between the episodes of transient slip; however, the elastic energy that accumulated due to locking of this deeper transitional zone between 2002 and 2006 appears to have been mostly or completed released by the 2004 and early 2006 transient slip events. The approximately balanced energy budget for the deeper zone of transient slip implies that this region is unlikely to contribute significant elastic energy to future earthquakes that originate along the seismogenic zone. Our results support a model in which seismic asperities coincide with regions of strong locking between earthquakes. The potential elastic energy that has re-accumulated since 1978 in the seismogenic zone is already sufficient to cause a repeat of the 1978 earthquake.
影响因子：
5.3
作者：
Ohta, Yusaku;Freymueller, Jeffrey T.;Suito, Hisashi
通讯作者：
Suito, Hisashi