Abstract In this study, we measured shear wave splitting (fast direction and delay time) from 5193 crustal earthquakes that occurred in the south Aegean that were recorded by 65 stations of the EGELADOS, GEOFON, and MedNet networks between November 2005-January 2007. We utilized the Multiple Filter Automatic splitting Technique (MFAST) that allows quick processing of thousands of events and obtained a total of 3732 high-quality measurements. In general, the majority of fast directions follows a trend of NNE-SSW or NNW-SSE, while the average delay time was found equal to 0.149 s. Analysis of the percentage of anisotropy with hypocentral depth indicates that the interval between 5-20 km exhibits up to 6% of crustal anisotropy with the majority of values being smaller than 4%. Comparison of the observed fast shear wave directions with the maximum horizontal stress (Shmax) shows that stress-induced anisotropy can explain the fast directions along the forearc (Peloponnese, Kythira strait, eastern Crete, Kasos, Karpathos, Rhodes) and SW Turkey. In the Cyclades most fast directions are significantly different from Shmax. Structural anisotropy is dominant in southern Peloponnese, in some parts of Crete and Karpathos. In Cyclades fast directions at several stations agree well with the stretching lineations along the exhumed metamorphic core complex and some major fault zones. A comparison of fast shear wave directions of crustal anisotropy with those of SKS mantle anisotropy shows good agreement in the forearc (Peloponnese, eastern Crete, Karpathos, Rhodes) as well as SW Turkey and suggests that the crust is deforming in the same direction with the mantle flow. This pattern becomes less clear in the Cyclades where stations near the metamorphic core complex exhibit good agreement, while others exhibit large deviations between the two fast directions and point to a possible decoupling of the two lithospheric units.

中文翻译：

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来自局部地震横波分裂的爱琴海南部地壳各向异性

摘要 在这项研究中，我们测量了 2005 年 11 月至 2007 年 1 月期间发生在爱琴海南部的 5193 次地壳地震的剪切波分裂（快方向和延迟时间），这些地震由 EGELADOS、GEOFON 和 MedNet 网络的 65 个台站记录。利用多重过滤器自动分裂技术 (MFAST)，可以快速处理数千个事件并获得总共 3732 次高质量的测量结果。一般来说，大多数快速方向遵循 NNE-SSW 或 NNW-SSE 的趋势，而平均延迟时间被发现等于 0.149 s。各向异性百分比随震源深度的分析表明，5-20 km 区间的地壳各向异性高达 6%，大部分值小于 4%。将观测到的快横波方向与最大水平应力 (Shmax) 进行比较，表明应力引起的各向异性可以解释沿弧前（伯罗奔尼撒半岛、基提拉海峡、克里特岛东部、卡索斯、卡尔帕索斯岛、罗得岛）和土耳其西南部的快速方向。在 Cyclades 中，大多数快速方向与 Shmax 明显不同。结构各向异性在伯罗奔尼撒半岛南部、克里特岛和卡尔帕索斯岛的一些地区占主导地位。在基克拉泽斯，几个站点的快速方向与沿挖掘出的变质核心复合体和一些主要断层带的拉伸线相吻合。地壳各向异性的快横波方向与 SKS 地幔各向异性的快横波方向的比较表明，在弧前（伯罗奔尼撒半岛、克里特岛东部、卡尔帕索斯岛、Rhodes) 以及 SW 土耳其，并表明地壳正在与地幔流相同的方向变形。这种模式在 Cyclades 中变得不太清楚，其中靠近变质核复合体的站点表现出良好的一致性，而其他站点则在两个快速方向之间表现出很大的偏差，并表明两个岩石圈单元可能脱钩。