P and S deep velocity structure of the Hellenic area obtained by robust nonlinear inversion of travel times
P and S deep velocity structure of the Hellenic area obtained by robust nonlinear inversion of travel times
复制标题
通过走时鲁棒非线性反演获得希腊地区的 P 和 S 深部速度结构
DOI：
--
复制
发表时间：
1997
期刊：
影响因子：
--
通讯作者：
G. Nolet
中科院分区：
文献类型：
--
作者：
C. Papazachos;G. Nolet
通过对当地事件走时的反演，得到了希腊弧爱琴海俯冲区岩石圈P和S速度结构的新模型。应用的反演技术是非线性的，因为采用了三维射线追踪。同时，为了减小射线密度对计算结果的影响，对最终线性化后的系统进行了适当的预处理。P-S的连贯性受VP/VS比的附加衰减控制。研究主要集中在爱琴海南部地区的希腊俯冲构造。俯冲板块的有趣特征和细节可以在最终的断层图像中辨认出来。在西部，板块较浅的部分以很小的角度倾斜(≃10°)。对于俯冲更深的部分，这一变化约为25°，导致在约70公里深度处有一个突出的扭结，这与伴生的贝尼奥夫带的一般特征一致。板块较小的东部并没有显示出相同的细节，但可以辨认出明显更陡峭的俯冲带。此外，还从速度结构中推断了地壳厚度变化的详细信息，并与现有的折射实验结果进行了很好的关联。最后，这些结果证实了最近关于在阿尔卑斯山带吸积棱柱的浅部(≃10-15公里)存在低速地壳层的说法。
We derived a new model for the P and S velocity structure of the lithosphere in the subduction area of the Hellenic arc and the Aegean Sea from the inversion of travel times of local events. The inversion technique applied is nonlinear, since three-dimensional ray tracing is incorporated. At the same time, an appropriate preconditioning of the final linearized system is used in order to reduce ray density effects on the results. The P-S coherency is controlled by an additional damping of the VP/VS ratio. The study focuses mainly on the structure of the Hellenic subduction in the southern Aegean region. Interesting features and details of the subducted slab can be recognized in the final tomographic images. On the western part, the shallower section of the slab is dipping at a very small angle (≃10°). This changes to approximately 25° for the deeper part of the subduction, resulting in a prominent kink at a depth of about 70 km, which is in accordance with the general characteristics of the associated Benioff zone. The smaller eastern part of the slab is not resolved with the same detail, but a clearly steeper subduction zone can be recognized. Moreover, detailed information about the crustal thickness variations are inferred from the velocity structure and correlate very well with the existing results from refraction experiments. Finally, the results confirm the recent suggestion concerning the existence of a low-velocity crustal layer at shallow depths (≃10–15 km) in the accretionary prism of the Alpine belt.