Upper-mantle structure beneath the southern Bohemian Massif and its surroundings imaged by high-resolution tomography
Upper-mantle structure beneath the southern Bohemian Massif and its surroundings imaged by high-resolution tomography
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高分辨率断层扫描成像的波希米亚地块南部及其周围地区下的上地幔结构
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发表时间：
2013
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通讯作者：
V. Babuška
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作者：
H. Karousová;J. Plomerová;V. Babuška
总结 我们提出了一种新的上地幔速度扰动模型，该模型通过波希米亚地块 (BM) 南部及其周围地区下方的远震层析成像技术检索到 300 公里以内的上地幔。尽管在欧洲的大规模层析成像研究中，地幔下方的上地幔表现为广泛的低速异质性，但我们基于被动实验 BOHEMA III 和 ALPASS 阵列北部的数据进行的区域研究也揭示了~40 km 尺度的速度特征。最明显的低速扰动集中在埃格尔裂谷下方约 200 公里处，而该裂谷下方更深处的速度则显示出相对于地幔地幔整体低速特征的高速扰动。断层扫描图像中主要存在两种显着的高速异质性。最独特和最广泛的一个，位于BM以南，我们与东部阿尔卑斯山根联系在一起。第二个高速异质性可以在地层中部下方 215 公里处的水平切片中追踪到。这些正扰动似乎从地块的西南部较浅的深度转移到了地基的东北部较深的地方。这种非均质性可以反映由于BM与来自东部的布鲁诺维斯图利亚(BV)微板块碰撞以及随后BV向BM的摩尔达努比亚部分下方的逆冲而导致的岩石圈增厚。
S U M M A R Y We present a new velocity-perturbation model of the upper mantle down to 300 km retrieved by teleseismic tomography beneath the southern part of the Bohemian Massif (BM) and its surroundings. Though the upper mantle beneath the BM appears as extensive low-velocity heterogeneity in large-scale tomography studies of Europe, our regional study based on data from passive experiment BOHEMA III and the northern part of the ALPASS array reveals also velocity features at scales of ∼40 km. The most distinct low-velocity perturbations concentrate along the Eger Rift down to ∼200 km, while velocities at greater depths beneath this rift show high-velocity perturbations relative to the overall low-velocity character of the BM mantle. Two significant high-velocity heterogeneities dominate the tomography images. The most distinct and extensive one, located south of the BM, we associate with the eastern Alpine root. The second high-velocity heterogeneity can be traced in horizontal slices down to 215 km beneath the central part of the BM. These positive perturbations seem to shift from the southwestern part of the massif at shallower depths to the northeastern part of the BM at greater depths. The heterogeneity can reflect the lithosphere thickening resulting from the collision of the BM with the Brunovistulian (BV) microplate from the east and the following underthrusting of the BV beneath the Moldanubian part of the BM.