Regional centroid moment tensors for earthquakes in the 2016 South Alboran seismic crisis

Data files and modelling results of regional centroid moment tensors obtained for earthquakes in the 2016 South Alboran seismic crisis, and presented in the article "Earthquake crisis reveals the development of an embryonic continental fault system”, by Eulàlia Gràcia et al. Large continental faults extend for thousands of kilometres to form boundaries between rigid tectonic blocks. These faults are often associated with prominent topographic features, and they can produce large earthquakes. Here we present first evidence of such a major tectonic structure in its initial growing stage, the Al-Idrissi Fault System (AIFS), in the Alboran Sea. Until now, this fault system had always been described as a complex diffuse boundary between Eurasia and Nubia plates. However, combining newly acquired high-resolution bathymetric and seismic reflection data, together with seismological analyses of the 2016 Mw 6.4 earthquake offshore Morocco – the largest event ever recorded in the area – we unveil a 3D geometry for the AIFS, which definitively correspond to a crustal-scale boundary. We report evidence of left-lateral strike-slip displacement, characterize fault segmentation and demonstrate that the AIFS is the source of the 2016 events. The occurrence of the Mw 6.4 earthquake together with historical and instrumental events supports that the AIFS is currently growing through propagation and linkage of its segments. Thus, the AIFS provides a unique model for inception and growth of a young continental fault system.

本数据集包含2016年南阿尔沃兰地震危机中地震的区域矩心矩张量（centroid moment tensor）数据文件与建模结果，相关研究成果发表于Eulàlia Gràcia等人的论文《地震危机揭示大陆断裂系统雏形的发育》（"Earthquake crisis reveals the development of an embryonic continental fault system"）。大型大陆断裂可延伸数千公里，构成刚性构造块体间的边界。此类断裂通常伴随显著地形特征，并可引发强震。本文首次报道了阿尔沃兰海（Alboran Sea）中处于初始发育阶段的大型构造结构——阿尔-伊德里斯断裂系统（Al-Idrissi Fault System, AIFS）的实证证据。此前，该断裂系统一直被视作欧亚板块与努比亚板块之间复杂的弥散型边界。本研究结合新获取的高分辨率水深测量与地震反射数据，以及对摩洛哥近海2016年Mw6.4级地震（该区域有仪器记录以来的最大地震事件）的地震学分析，揭示了阿尔-伊德里斯断裂系统的三维几何形态，证实其属于地壳尺度的构造边界。我们报道了左旋走滑位移的相关证据，刻画了断层分段特征，并证实阿尔-伊德里斯断裂系统正是2016年地震事件的震源。此次Mw6.4级地震的发生，结合历史地震与仪器记录地震事件的佐证，表明阿尔-伊德里斯断裂系统目前正通过各分段的扩展与连接持续发育。因此，该断裂系统为年轻大陆断裂系统的起始与演化提供了独一无二的研究模型。