Western U.S. upper mantle structure
Western U.S. upper mantle structure
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DOI：
10.1029/93jb01724
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发表时间：
1994-05
影响因子：
--
通讯作者：
E. Humphreys;K. Dueker
中科院分区：
文献类型：
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作者：
E. Humphreys;K. Dueker
上曼德P波速度结构的区域三维反演是从美国西部运行的许多高密度高频区域阵列记录的超声波P波走时残差中创建的。这些反演调整到一个全球（国际地震中心）的参考和合并，以获得美国西部下的上地幔的图像。上地幔的P波速度平均较慢，结构非常不均匀。在分辨率较好的地方，相干上地幔结构的成像深度可达200 km（Juan de Fuca和Gorda板例外，穿透深度更深），与平均速度（在给定深度）的偏差高达± 4%。这些构造的横向分辨率通常很好，尽管实际地震变化的幅度可能大于成像的幅度。成像的地幔结构的长波长部分限定了具有200-500 km波长的相干伸长特征。在太平洋沿岸约1250 km范围内，这些构造的波长约为1250 km，其走向与地表地貌和年轻构造平行。在大陆内部之下，利用额外的地震研究来推断地震数据覆盖率低的地区的平均结构，结构的波长为1500公里，并向东北方向发展。这种东北方向与年轻的构造结构不一致，但与年轻的火山活动一致。
Regional three-dimensional inversions of upper mande P wave velocity structure are created from teleseismic P wave travel time residuals recorded by many of the high-density high-frequency regional arrays operated within the western United States. These inversions are adjusted to a global (International Seismic Centre) reference and merged to obtain an image of the upper mantle beneath western United States. The P wave velocities in the upper mantle are slow on average, and the structure is very heterogeneous. Where resolution is good, coherent upper mantle structures are imaged that extend as deep as ∼200 km (the Juan de Fuca and Gorda slabs, which penetrate to greater depths, are exceptions) and deviate from the average velocity (at a given depth) by as much as ±4%. Lateral resolution of these structures usually is very good, although the magnitude of the actual seismic variations is probably greater than that imaged. The long wavelength part of the imaged mantle structure defines coherent elongate features with wavelengths of 200–500 km. Within ∼250 km of the Pacific Coast, these structures have a wavelength of ∼250 km and trend parallel to the surface physiography and young tectonic structures. Beneath the continental interior, where use is made of additional seismic studies to infer average structure in regions of poor teleseismic data coverage, structures have a wavelength of ∼500 km and trend northeasterly. This northeast orientation is discordant with young tectonic structures but aligns with young volcanic activity.