Seismic imaging of the interplate boundary and deformation within the overriding Aegean lithosphere at the Hellenic subduction zone west of Crete (Greece)

世界上大部分的大地震都发生在俯冲带，或称“巨型逆冲断层”。这些事件对人口稠密的沿海地区构成重大的地震和海啸危险。该项目的重点是东地中海的希腊俯冲带，这是欧洲地震最活跃的地区。这个俯冲带呈现出一个明显的悖论，即目前的大逆冲断层似乎是弱耦合的，在最大震级为~6的事件中破裂，但这个系统在历史上能够产生M8海啸地震，例如公元365年克里特岛西部南部的M8.3事件，这是欧洲有史以来报道的最大事件。 这个项目将有助于解决这个矛盾，通过提高我们的知识的几何形状和性质的板块界面和其他故障在希腊俯冲带。更好地限制这个俯冲带的深层结构对于评估人口稠密的地中海沿海地区的危害至关重要。对希腊俯冲带的研究也将有益于对其他俯冲带的研究，如美国卡斯卡迪亚和阿拉斯加边缘。 该项目涉及与法国和希腊科学家的强有力的国际合作，资金支持对希腊俯冲带火山弧进行多通道地震调查。获取这些数据利用了一个独特的机会，以成像的俯冲带的孕震部分。这些数据将通过R/V Marcus Langseth的深穿透反射地震能力沿着克里特岛以西220公里长的剖面采集，穿过AD 365地震的推断破裂区。这些数据将提供关于板块边界总体几何形状的重要缺失信息，包括沿板块边界沿着俯冲的沉积物厚度、板间粗糙度和与其他地方观察到的板间性质变化有关的可能下倾变化，从而大大提高对这一地区俯冲动力学和过程的了解。这些数据将与该项目的法国合作伙伴在2012年获得的同地海底地震仪广角反射-折射数据一起进行分析和解释。地震活动性研究表明覆盖板块中存在一个或多个活动特征，最近一些作者提出，过去的大地震可能发生在展布断层上，而不是发生在主板块边界上。地震反射剖面图将反映上覆板块的特征及其与巨型逆冲断层的关系，并使我们能够区分活动断层和以往构造事件的遗迹构造。这些特征的几何形状将对这些特征的海啸潜在性提供重要的限制。除了国际合作外，更广泛的影响包括支持一位早期职业女性科学家，并通过首次测试新的R/V Marcus Langseth长偏移拖缆来加强研究基础设施。

Most of the world's great earthquakes occur at subduction zones, or "megathrusts". These events pose significant earthquake and tsunami hazards to densely populated coastal areas. This project focuses on the Hellenic subduction zone in Eastern Mediterranean, which is the most seismically active region in Europe. This subduction zone presents an apparent paradox in that the megathrust appears to be weakly coupled at present, rupturing in events with maximum magnitudes of ~6, but this system has been capable of producing M8 tsunamigenic earthquakes in historical time such, as the 365 AD M 8.3 events south of western Crete which is the largest event ever reported in Europe. This project will help resolve this paradox by improving our knowledge of the geometry and properties of the plate interface and other faults in the Hellenic subduction zone. Better constraints on the deep architecture of this subduction zone are essential for assessing hazards for the densely populated Mediterranean coastal regions. The study of the Hellenic subduction zone will also benefit studies of other subduction zones, such as the US Cascadia and Alaska margins. This project involves a strong international collaboration with French and Greek scientists.Funding supports a multichannel seismic survey of the volcanic arc of the Hellenic subduction zone. Acquiring these data takes advantage of a unique opportunity to image the seismogenic part of this subduction zone. The data will be acquired with the deep penetration reflection seismic capabilities of the R/V Marcus Langseth along a 220-km-long profile west of Crete, across the inferred rupture area of the AD 365 earthquake. These data will provide important missing information on the overall geometry of the plate boundary including the thickness of sediment subducting along the plate boundary, interplate roughness and possible downdip variations related to changes in the properties of the interplate, as have been observed elsewhere, allowing a much-improved understanding of the subduction dynamics and processes in this area. The data will be analyzed and interpreted together with co-located ocean bottom seismometer wide-angle reflection-refraction data acquired in 2012 by French partners of this project. Seismicity studies indicate one or more active features in the overriding plate, and some authors recently suggested that past great earthquakes might have occurred on a splay fault rather than on the main plate boundary. The seismic reflection profile will image features in the overriding plate and their relationship to the megathrust and will allow us to distinguish between active faults and relic structures from previous tectonic events. The geometry of these features will provide important constraints on the tsunamigenic potential of these features. In addition to international collaborations, broader impacts include support of an early career female scientist and enhancement of research infrastructure through the first test of the new R/V Marcus Langseth long-offset streamer.