Lithospheric structure of the Tornquist Zone resolved by nonlinear P and S teleseismic tomography along the TOR array
Lithospheric structure of the Tornquist Zone resolved by nonlinear P and S teleseismic tomography along the TOR array
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DOI：
10.1016/j.tecto.2005.11.019
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发表时间：
2006-04
期刊：
影响因子：
2.9
通讯作者：
Z. Shomali;R. Roberts;L. Pedersen
中科院分区：
文献类型：
--
作者：
Z. Shomali;R. Roberts;L. Pedersen
TOR项目的主要目的是研究横跨德国北部、丹麦和瑞典南部的索尔根弗里-托恩奎斯特带下的岩石圈-软流圈边界结构。利用TOR台阵记录的51个地震的远震P、S震相的到时相对残差，圈定了研究区的地震过渡带。根据从其他数据得到的三维地壳模型，通过对地壳中走时变化的远震残差进行校正，研究了地壳结构的影响。对S震相进行了反演。然后将计算结果与相应的P波模型进行比较。正如预期的那样，推导出的模型表明，相对古老和寒冷的波罗的海盾比更南边较年轻的岩石圈有更高的深度速度。这些模型显示，当我们从南向北移动时，速度在深度上有两个明显的急剧增加，与我们的参考模型相比是低的。这些边界的位置和锐度表明，所解析的特征至少部分是成分起源的，推测与地幔耗竭有关。发现一条陡峭而陡峭的次地壳边界与瑞典南部边缘大致重合。根据地表地质证据，这低于通常放置波罗的海盾牌边缘的位置(索尔根弗里-托恩奎斯特区)。另一个不太重要的转变或多或少被认为是在易北克阵容之下的。剖面中部(丹麦)下相对较高的d(Vp/vs)比值表明，在重力高支持广泛镁铁质侵入体假说的地区，S速度相对较低。
The main aim of the TOR project is to study the lithospheric–asthenospheric boundary structure under the Sorgenfrei–Tornquist Zone, across northern Germany, Denmark and southern Sweden. Relative arrival-time residuals of teleseismic P and S phases from 51 earthquakes, recorded by 150 seismic stations along the TOR array, were used to delineate the transition zone in the studied area. The effects of crustal structures were investigated by correcting the teleseismic residuals for travel-time variations in the crust based on a 3D crustal model derived from other data. The inversion was carried out for S phases. The results were then compared with the corresponding P-wave models. As expected, the derived models show that the relatively old and cold Baltic Shield has higher velocity at depth than the younger lithosphere farther South. The models show two sharp and distinct increases in depth to velocities which are low compared to our reference model, as we move from South to North. The location and sharpness of these boundaries suggests that the features resolved are, at least partially, compositional in origin, presumably related to mantle depletion. A sharp and steep subcrustal boundary is found roughly coincident with the southern edge of Sweden. This is below where the edge of the Baltic Shield is usually placed, based on surface geological evidence (the Sorgenfrei–Tornquist Zone). Another less significant transition is recognised more or less beneath the Elbe-lineament. Relatively high d(Vp/Vs) ratios under the central part of the profile (Denmark) indicate relatively low S-velocity in an area where a gravity high supports the hypothesis of extensive mafic intrusions.