Three-dimensional velocity models can enable accurate earthquake location, improved seismic hazard assessment, and can enhance our understanding of geodynamic processes. This is particularly true for areas such as the Aegean, where the crust is marked by active volcanoes as well as shear and rift zones, all of which make this region highly heterogeneous. This work describes the application of local earthquake tomography in order to elucidate the crustal structure of the Aegean. We utilized a dataset of 2,135,625 P arrivals and 1,095,515 S arrivals from 178,676 events recorded across 324 stations. Results indicate that the boundary separating the slow V from the fast anomalies at 20–40 km depth is well correlated with the Aegean Moho obtained from receiver functions. A slow V (−5%) zone at depths >30 km along the Hellenic arc is likely associated with basal underplating that forms the base of the crust. On the other hand, fast V and moderate to high V/V (1.77–1.92) in the upper-middle crust may indicate evolving metamorphic core complexes. Steeply dipping clusters of earthquakes could highlight pathways of fluid migration from the base to the middle/upper crust, albeit more detailed seismological studies are needed to confirm this interpretation. The 3D velocity model can be also utilized in order to investigate the amount of melt fraction beneath active volcanoes and the influence of fluids on the rupture zone of large earthquakes. Our results show a melt fraction between 4 and 10% beneath active volcanoes, with the largest volume of melt present beneath Santorini caldera. The ruptures zones of 10 large earthquakes (M ≥ 6.0), show slow V anomalies and moderate to high V/V (> 1.77), suggesting that these events were likely triggered by weakening of their source zones by fluid activity.

中文翻译：

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爱琴海地壳的局部地震层析成像：对活动变形、大地震和弧火山活动的影响


三维速度模型可以实现准确的地震定位，改进地震危险性评估，并可以增强我们对地球动力学过程的理解。对于爱琴海等地区来说尤其如此，那里的地壳以活火山以及剪切带和裂谷带为标志，所有这些都使该地区高度异质。这项工作描述了当地地震层析成像的应用，以阐明爱琴海的地壳结构。我们使用了 324 个站点记录的 178,676 个事件中包含 2,135,625 个 P 到达和 1,095,515 个 S 到达的数据集。结果表明，在 20-40 公里深度处将慢 V 波与快异常区分开的边界与从接收器函数获得的爱琴海莫霍面有很好的相关性。沿希腊弧深度 >30 公里的慢 V (−5%) 区域可能与形成地壳底部的基底底侵作用有关。另一方面，中上地壳中的快 V 和中至高 V/V (1.77-1.92) 可能表明正在演化的变质核杂岩。急剧倾斜的地震群可以突出流体从地壳到中/上地壳的迁移路径，尽管需要更详细的地震学研究来证实这种解释。还可以利用 3D 速度模型来研究活火山下方的熔体部分量以及流体对大地震破裂带的影响。我们的结果显示，活火山下方的熔化分数在 4% 至 10% 之间，其中圣托里尼火山口下方的熔化量最大。 10次​​大地震（M≥6.0）的破裂带显示出慢V异常和中到高V/V（> 1.77），表明这些事件可能是由于流体活动削弱其源区而引发的。