Deformation across the forearc of the Cascadia subduction zone at Cape Blanco, Oregon
Deformation across the forearc of the Cascadia subduction zone at Cape Blanco, Oregon
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俄勒冈州布兰科角卡斯卡迪亚俯冲带前弧的变形
DOI：
10.1029/1999jb900392
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发表时间：
2000
影响因子：
--
通讯作者：
M. Murray
中科院分区：
文献类型：
--
作者：
J. C. Savage;J. Svarc;W. Prescott;M. Murray
在1992-1999年期间，美国地质调查局测量了从俄勒冈州海岸的布兰科角到纽贝里火山口附近的火山弧（距离变形锋分别为55公里和350公里）延伸到N80°E（板块会聚的近似方向）的大地测量阵列的变形。在距变形锋约150 km的范围内，弧前正与俯冲的胡安·德富卡板块耦合，向弧形方向（N80°E）压缩。观测到的N80°E压缩的位错模型表明，主逆冲带（Juan de Fuca-前弧界面的锁定部分）在下倾方向上约为40 km宽。相对于北美固定的内部，测得的弧前的横向（N10°W）速度分量随着距离变形锋的距离而减小，速率约为0.03 mm yr−1 km−1。这种梯度似乎是前弧板块相对于固定的北美内陆刚性旋转的结果（欧拉矢量为43.4°±0.1°N，120.0°±0.4°W和-1.67 ±0.17 °（m.y.））。-1;引用的不确定度为标准差）。自转速率与古地磁测量的自转速率（−1.0±0.2 °（百万年））相似。-1）15 Ma熔岩流沿着哥伦比亚河向北250 km。后弧似乎并没有参与这种自转，而是以每年3.6毫米的速度向北迁移。这种迁移可能部分是由于我们的参考坐标系与北美内陆的不完美联系造成的。
Over the interval 1992–1999 the U.S. Geological Survey measured the deformation of a geodetic array extending N80°E (approximate direction of plate convergence) from Cape Blanco on the Oregon coast to the volcanic arc near Newberry Crater (55 and 350 km, respectively, from the deformation front). Within about 150 km from the deformation front, the forearc is being compressed arcward (N80°E) by coupling to the subducting Juan de Fuca plate. Dislocation modeling of the observed N80°E compression suggests that the main thrust zone (the locked portion of the Juan de Fuca-forearc interface) is about 40 km wide in the downdip direction. The transverse (N10°W) velocity component of the forearc measured with respect to the fixed interior of North America decreases with distance from the deformation front at a rate of about 0.03 mm yr−1 km−1. That gradient appears to be a consequence of rigid rotation of the forearc block relative to fixed interior North America (Euler vector of 43.4°±0.1°N, 120.0°±0.4°W, and −1.67±0.17 ° (m.y.)−1; quoted uncertainties are standard deviations). The rotation rate is similar to the paleomagnetically measured rotation rate (−1.0±0.2 °(m.y.)−1) of the 15 Ma lava flows along the Columbia River 250 km farther north. The back arc does not appear to participate in this rotation but rather is migrating at a rate of about 3.6 mm yr−1 northward with respect to fixed North America. That migration could be partly an artifact of an imperfect tie of our reference coordinate system to the interior of North America.