A New Look at the Seismic Velocity Structure of the Oceanic Crust (Paper 80R0584)
A New Look at the Seismic Velocity Structure of the Oceanic Crust (Paper 80R0584)
复制标题
对洋壳地震速度结构的新认识（论文 80R0584）
DOI：
10.1029/rg018i003p00627
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发表时间：
1980
影响因子：
5.2
通讯作者：
J. Orcutt
中科院分区：
文献类型：
--
作者：
P. Spudich;J. Orcutt
在过去的十年里，由于地震实验设计、仪器和分析技术的进步，一幅海洋地壳的新图景出现了。在这张新图片中，第2层是一个速度随深度迅速增加的区域。虽然有证据表明在第2层中有更精细的结构，但这种结构的确切性质仍然没有得到很好的解决。第3层在垂直方向上比第2层均匀得多，垂直速度梯度平缓，在νp和ν中偶有低速带。虽然在几个地点已经观察到高速基底地壳层的普遍存在，但这是一个疑问。据观察，地壳-地幔过渡的厚度在不同地点之间的变化在0到2公里之间，即使在平坦、不复杂的地点，也可以在几公里的尺度上找到横向非均质性的地震证据。地壳的地震图像与蛇绿岩复合体岩石的地震速度很好地一致，并且与在高压下多孔、水饱和岩石的地震速度的理论预期行为一致。综述了利用合成地震记录模拟技术获得的速度结果，并介绍了适合海洋工作的合成技术的类型。
Within the last decade a new picture of the oceanic crust has emerged from advances in seismic experimental design, instrumentation, and analysis techniques. In this new picture, layer 2 is a region in which velocity increases rapidly with depth. While there is evidence of finer structure within layer 2, the exact nature of this structure is still poorly resolved. Layer 3 is much more homogeneous vertically than layer 2 and appears to have gentle vertical velocity gradients and occasional low-velocity zones in νp and νs. Although it has been observed at several sites, the widespread existence of a high-velocity basal crustal layer is in doubt. The thickness of the crust-mantle transition has been observed to vary between 0 and 2 km from site to site, and even at flat lying, uncomplicated sites, seismic evidence for lateral heterogeneities on a scale of a few kilometers can be found. This seismic picture of the crust is in good agreement with the seismic velocities of rocks from ophiolite complexes and is consistent with the theoretically expected behavior of seismic velocities in porous, water-saturated rocks at elevated pressures. A review of velocity results obtained from use of synthetic seismogram modeling techniques is given, and the types of synthetic techniques suitable for marine work are described.