Mapping crustal stress and strain in southwest British Columbia
Mapping crustal stress and strain in southwest British Columbia
复制标题
绘制不列颠哥伦比亚省西南部的地壳应力和应变图
DOI：
10.1029/2010jb008003
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发表时间：
2011
影响因子：
--
通讯作者：
S. Mazzotti
中科院分区：
文献类型：
--
作者：
N. Balfour;N. Balfour;J. Cassidy;J. Cassidy;S. Dosso;S. Mazzotti;S. Mazzotti
[1]本文利用震源机制数据的贝叶斯反演结果，并与GPS短期应变率进行比较，研究了不列颠哥伦比亚省西南部卡斯卡迪亚俯冲带弧前的应力方向和应力来源。该地区的俯冲边缘包括从华盛顿州的N-S向到不列颠哥伦比亚省的NW-SE向的方向变化。计算了1,000多个北美地壳地震的震源机制，以确定断裂的主要类型，并反演了∼600，以估计主应力方向和应力比。我们的结果表明，最大水平压应力方向随距离海沟的距离而变化，从沿海岸近似边缘正常到距海岸内陆约100-150公里。将应力方向与GPS数据进行比较，我们将边缘-法向应力方向与俯冲相关的应变率联系起来，这是由于北美板块和胡安德富卡板块之间的界面锁定，就在温哥华岛以西。北美洲板块边缘平行的最大水平压应力与俄勒冈地块的北推有关，在俯冲分量去除后，在残余应变率的水平缩短方向上也可以观察到这一点。
[1] This paper investigates the orientation and sources of stress in the forearc of the Cascadia subduction zone in southwest British Columbia, using Bayesian inversion results from focal mechanism data and comparing results with GPS derived short-term strain rates. The subduction margin in this region includes a change in orientation from N-S in Washington State to NW-SE in British Columbia. Over 1000 focal mechanisms from North American crustal earthquakes have been calculated to identify the dominant style of faulting, and ∼600 were inverted to estimate the principal stress orientations and the stress ratio. Our results indicate the maximum horizontal compressive stress orientation changes with distance to the trench, from approximately margin-normal along the coast to approximately margin-parallel 100–150 km inland from the coast. Comparing stress orientations with GPS data, we relate the margin-normal stress direction to subduction-related strain rates due to the locked interface between the North American and Juan de Fuca plates just west of Vancouver Island. Further from the margin the plates are coupled less strongly, and the margin-parallel maximum horizontal compressive stress in the North American Plate relates to the northward push of the Oregon Block, which is also observed in the horizontal shortening direction of the residual strain rates, after the subduction component is removed.