We analyzed waveform inversion focal mechanisms of earthquakes that occurred in the last decades in the Calabrian Arc region, the most seismic area of Italy according to historical catalogs and the only where active subduction can be still found along the Nubia-Eurasia convergent margin. We focused our analysis on earthquakes shallower than 40 km and, in order to reduce the effects of very local scale processes, with magnitude 4.0 and larger. Hypocenters of the individual earthquakes with their uncertainties have been compared with location and geometry of the Calabrian Subduction Interface (CSI), reconstructed by previous investigators, with the purpose of associating the individual earthquakes and their focal mechanisms to the shallower part of the Ionian subducting plate (lower plate) or to the Tyrrhenian overriding plate (upper plate). By integrating focal mechanisms available from literature and catalogs with those properly estimated in this study we obtained a dataset of 31 focal mechanism solutions. Considering the focal depth of each earthquake and the CSI depth in the relative epicentral area, only one of the selected earthquakes could not be univocally associated to one of the two domains (lower or upper plate). The other 30 FMs show an evident west-east separation between the western earthquakes of the Tyrrhenian Sea and mainland Calabria occurring in the upper plate domain (17 earthquakes), and the eastern ones of the Calabria Ionian shore and relative offshore occurring in the lower plate domain (13 earthquakes). The focal mechanism distribution highlights clear extension in the Tyrrhenian overriding plate with opening direction trending roughly perpendicular to the Calabrian Arc mountain chain. The situation appears quite more complex in the Ionian lower plate where seismic faulting indicates marked heterogeneity with prevailing compressional features. These results are discussed together with the information available in the literature for the study area concerning historical earthquakes and relative sources, tectonic stress distributions, geodetic crustal velocities and related strain rates. Finally, we comment our findings in the light of recent geodynamic models proposed in the literature for the same area and for the wider central Mediterranean region.

我们分析了卡拉布里亚弧形地区近几十年来发生的地震的波形反演震源机制，卡拉布里亚弧形地区是根据历史记录，在意大利地震多发地区，也是唯一在努比亚-欧亚大陆会聚边缘仍能活跃俯冲的地方。我们将分析的重点放在40公里以下的地震上，以减少局部规模大于4.0级的地震的影响。已将单个地震的震源及其不确定性与以前的研究人员重建的卡拉布布俯冲界面（CSI）的位置和几何形状进行了比较，目的是将单个地震及其震源机制与爱奥尼亚俯冲板块的较浅部分相关（下图）或第勒尼安斯上覆图（上图）。通过将文献和目录中提供的震源机制与本研究中正确估计的震源机制相结合，我们获得了31个震源机制解的数据集。考虑到每次地震的震源深度和相对震中区域的CSI深度，只有选定的地震之一不能与两个区域之一（下板块或上板块）唯一相关。其他30次FM显示在上板块区域发生的第勒尼安海西部地震和卡拉布里亚大陆西部地震之间有明显的东西向分离（17次地震），而下板块发生的卡拉布里亚爱奥尼亚海岸东部和相对海上地震之间则是明显的东西向分离。域（13次地震）。震源机制分布突显出第勒尼安覆岩板块的清晰延伸，其张开方向大致垂直于卡拉布里亚弧山脉。这种情况在爱奥尼亚下部板块中显得更为复杂，那里的地震断层表明明显的非均质性并具有普遍的压缩特征。讨论了这些结果，并结合了文献中有关历史地震和相关震源，构造应力分布，大地壳速度和相关应变率的信息。最后，我们根据文献中针对同一地区以及地中海中部地区提出的最新地球动力学模型，对我们的发现进行评论。这种情况在爱奥尼亚下部板块中显得更为复杂，那里的地震断层表明明显的非均质性并具有普遍的压缩特征。讨论了这些结果，并结合了文献中有关历史地震和相关震源，构造应力分布，大地壳速度和相关应变率的信息。最后，我们根据文献中针对同一地区以及地中海中部地区提出的最新地球动力学模型，对我们的发现进行评论。这种情况在爱奥尼亚下部板块中显得更为复杂，那里的地震断层表明明显的非均质性并具有普遍的压缩特征。讨论了这些结果，并结合了文献中有关历史地震和相关震源，构造应力分布，大地壳速度和相关应变率的信息。最后，我们根据文献中针对同一地区以及地中海中部地区提出的最新地球动力学模型，对我们的发现进行评论。大地壳速度和相关应变率。最后，我们根据文献中针对同一地区以及地中海中部地区提出的最新地球动力学模型，对我们的发现进行评论。大地壳速度和相关应变率。最后，我们根据文献中针对同一地区以及地中海中部地区提出的最新地球动力学模型，对我们的发现进行评论。