A unified three-dimensional model of the lithospheric structure at the subduction corner in southeast Alaska: Summary results from STEEP
A unified three-dimensional model of the lithospheric structure at the subduction corner in southeast Alaska: Summary results from STEEP
复制标题
DOI：
10.1130/ges01488.1
复制
发表时间：
2019-04
期刊：
影响因子：
2.5
通讯作者：
G. Pavlis;M. Bauer;J. Elliott;P. Koons;T. Pavlis;N. Ruppert;K. Ward;L. Worthington
中科院分区：
文献类型：
--
作者：
G. Pavlis;M. Bauer;J. Elliott;P. Koons;T. Pavlis;N. Ruppert;K. Ward;L. Worthington
我们合并从圣埃利亚斯侵蚀/构造项目（STEEP），其他研究和地震活动性数据的结构结果，建立一个全面的，三维模型的岩石圈的俯冲角在阿拉斯加南部。该模型由三个表面定义：（1）俯冲岩石圈表面的顶部，（2）莫霍面，（3）俯冲岩石圈表面的底部。我们使用雅库特微板块南端作为锚来模拟俯冲岩石圈的东部边缘。使用该锚的运动学重建表明，现代费尔韦瑟断层可能继承了6-10 Ma期间的边缘运动。建立了圣埃利亚斯山附近地壳形变的四维运动学模型。我们称这个模型为middlebuster模型，因为它的几何形状类似于同名的双面犁。犁的西侧是阿留申巨型逆冲断层的东部界限，该逆冲断层是由1979年圣埃利亚斯地震的STEEP地震结果和滑动模型的约束条件结合而成的。东侧是根据1899年雅库特湾地震序列的地质测绘和滑动模型推断的。犁的顶部靠近苏厄德冰川，以前的研究表明那里的挖掘率接近世界纪录。GPS速度矢量显示在圣伊莱亚斯山的结合处有一个大的旋转。在构造结以西，从GPS数据反演推断出的断层位于从地震成像推断出的巨型逆冲断层之上。这一证据和其他证据表明，在雅库塔特微板块缝合线附近的地区，存在一个韧性地壳楔，它部分地将俯冲地幔岩石圈从上地壳中分离出来。
We merge structural results from the ST. Elias Erosion/tectonics Project (STEEP), other studies, and seismicity data to build a comprehensive, three-dimensional model of the lithosphere of the subduction corner in southern Alaska. The model is defined by three surfaces: (1) a top of the subducting lithosphere surface, (2) Moho surfaces, and (3) a base of subducting lithosphere surface. We model the eastern edge of the subducting lithosphere using the southern tip of the Yakutat microplate as an anchor. Kinematic reconstructions using that anchor suggest the modern Fairweather fault is likely inherited from motion of the margin in the 6–10 Ma period. We constructed a 4D kinematic model of crustal deformation in the vicinity of Mount St. Elias. We call this model the middlebuster model because the geometry is similar to a two-sided plow with that name. The west side of the plow is the eastern limit of the Aleutian megathrust constructed from the union of constraints from STEEP seismic results and slip models of the 1979 St. Elias earthquake. The east side is inferred from geologic mapping and slip models of the 1899 Yakutat Bay earthquake sequence. The top of the plow is near the Seward Glacier, where previous studies showed near world-record exhumation rates. GPS velocity vectors show a large rotation across the syntaxis at Mount St. Elias. West of the syntaxis, faults inferred from inversion of the GPS data are above the megathrust inferred from seismic imaging. That and other evidence suggest the presence of a wedge of ductile crust that partially decouples the subducting mantle lithosphere from the upper crust in the area near the suture with the Yakutat microplate.