A regional shear-wave velocity model in the central Vøring Basin, N. Norway, using three-component Ocean Bottom Seismographs
A regional shear-wave velocity model in the central Vøring Basin, N. Norway, using three-component Ocean Bottom Seismographs
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DOI：
10.1016/s0040-1951(98)00093-6
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发表时间：
1998-08
期刊：
影响因子：
2.9
通讯作者：
P. Digranes;R. Mjelde;S. Kodaira;H. Shimamura;T. Kanazawa;H. Shiobara;E. Berg
中科院分区：
文献类型：
--
作者：
P. Digranes;R. Mjelde;S. Kodaira;H. Shimamura;T. Kanazawa;H. Shiobara;E. Berg
区域海底地震仪（OBS）数据集在Vøring盆地的中部和北方获得，N。挪威，1992年。沿沿着7个区域剖面布设了30个三分量OBS，利用已建立的P波模型，利用二维射线追踪模拟了水平分量上记录的剪切波。在浅部（1- 4km深度），沿沿着NW-SE和NE-SW向剖面的平均Vp/Vs比值分别为2.1-2.2和2.3-2.5。在这个区间相对较高的平均Vp/Vs比值可能与最上层的松散沉积物有关。Vp/Vs比的方位角变化与快速方向NW-SE，表明在这个间隔的剪切波各向异性为5-10%，与观测进一步北在罗弗敦地区。在5-10 km深度范围内，沉积物中的高速岩床侵入体由P波模拟绘制。这些高速侵入体作为有效的转换接口，证实了剪切波建模。在4-6 km深度处，Vp/Vs比值区域性地降低到1.7-1.8，这可能与白垩纪中期的富砂沉积有关。剪切波清晰地映射了上地壳，推断的Vp/Vs比为1.75，证实了Vøring盆地的地壳是大陆起源的。下地壳Vp/Vs比值（1.8-1.85）的增加表明其组成发生了变化，这可能是由大陆地壳和岩浆底侵作用的“混合”造成的。
A regional Ocean Bottom Seismometer (OBS) dataset was acquired in the central and northern part of the Vøring Basin, N. Norway, in 1992. Thirty three-component OBSs were deployed along seven regional profiles, and the shear waves recorded on the horizontal components have been modelled by use of 2-D ray-tracing utilizing an established P-wave model. In the shallow sediments (1–4 km depth) mean Vp/Vsratios of 2.1–2.2 and 2.3–2.5 are inferred along the NW–SE- and NE–SW-trending profiles, respectively. The relatively high mean Vp/Vsratios in this interval are probably related to unconsolidated sediments in the uppermost layers. The azimuthal variation in the Vp/Vsratios with the fast direction NW–SE, indicates a shear-wave anisotropy of 5–10% in this interval, consistent with observations further north in the Lofoten area. In the 5–10 km depth interval high-velocity sill intrusions in the sediments are mapped by the P-wave modelling. These high-velocity intrusions act as efficient conversion interfaces, confirmed by the shear-wave modelling. A regional decrease in the Vp/Vsratios to 1.7–1.8 are observed at 4–6 km depth, possibly related to sand-rich sediments in the middle Cretaceous. The upper crust is clearly mapped by the shear waves, and the inferred Vp/Vsratio of 1.75 confirms that the crust in the Vøring Basin is of continental origin. An increase of the Vp/Vsratio (1.8–1.85) in the lower crust indicates a change in its composition, possibly explained by a `mixing' of continental crust and magmatic underplating.