Generation and Destruction of Lithosphere in the Ligurian Sea

利古里亚海岩石圈的生成与破坏

• 批准号: 365287383
• 负责人: Dr. Dietrich Lange
• 金额: --
• 依托单位: GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/365287383?language=en
• 关键词: Generation; Destruction; Lithosphere; Ligurian; Sea

The convergence of the Africa and the Eurasia plates and the recent evolution of the western Mediterranean-Alpine area has built a puzzle of basins (such as the Ligurian Sea) and ranges. The Ligurian sea is a key location due to its complex geodynamic setting characterized by pronounced variations in crustal nature and thickness. The deep structure is characterized by the transition from the western Alpine orogen to the Apennine system and change in subduction polarity. Beneath the Ligurian Sea the Alpine front subducts to the East while beneath the Apennine eastward subduction and subduction rollback advancing to the NW occurs. In particular for larger depths (>20 km) no seismological imaging using OBS data was carried out and the knowledge of the deep structure in the Ligurian sea is mostly inferred from land data observations or from very large-scale tomography studies. In order to image the lithospheric structure we propose to use the data from 33 broadband Ocean Bottom Seismometer (OBS) stations from the LOBSTER deployment in the Ligurian Sea and adjacent landstations. The OBS stations form the marine component of the AlpArray installed within the framework of the SPP 4D-MB and will be installed in May/June 2017 in the Ligurian sea for a period of ~11 months. We propose seismological ambient noise cross correlation techniques in order to estimate empirical Green functions between the receivers. The extracted group velocities of the Rayleigh waves will be complemented with Rayleigh wave phase velocity dispersion curves from distant earthquakes in order to enhance the quality of the dataset for the inversion of a 3D shear velocity model. The shear wave velocity model will be used to discriminate between previously hypothesed nature of the basin center such as serpentinized, typical oceanic crust or underplated material. In particular, the geometry of the oceanic crust in the basin is of special interest in relation with the major geodynamic events that shaped it.The current seismicity rate is in the Ligurian Sea is modest with magnitude 4-4.5 events with an approximate period of 2-3 years. Despite the moderate seismicity level destructive earthquakes occurred in the region in historical times such as the Imperia earthquake 1897 in the centre of the basin (Mw 6.3-7.5) with at least 600 casualties. The LOBSTER OBS network will allow for the first time precise determination of seismic moment release with homogenous resolution down to small magnitude events (Ml 1-2) resulting in the identification of active faults and their seismogenic depths involved in current basin opening. Current locations and properties of active faults are poorly known and a thorough analysis of the local seismicity will enlighten the shallow geology and possibly the stress regime (from focal mechanisms) in the Ligurian basin.

非洲板块和欧亚板块的会聚以及西地中海-阿尔卑斯地区的近期演化，形成了一个盆地（如利古里亚海）和山脉的拼图。利古里亚海是一个关键地点，因为其复杂的地球动力学背景，其特点是地壳性质和厚度变化明显。深部构造特征为西阿尔卑斯造山带向亚平宁系的过渡和俯冲极性的变化。在利古里亚海之下，阿尔卑斯锋面向东俯冲，而在亚平宁海之下，则发生向东俯冲和向西北推进的俯冲回滚。特别是对于较大深度（>20公里），没有使用光学基片扫描数据进行地震成像，对利古里亚海深层结构的了解主要是从陆地数据观测或超大规模层析成像研究中推断出来的。为了成像的岩石圈结构，我们建议使用的数据从33个宽带海底地震仪（OBS）站部署在利古里亚海和邻近的陆地站。OBS站构成了安装在SPP 4D-MB框架内的AlpArray的海洋组件，将于2017年5月/6月在利古里亚海安装，为期约11个月。我们提出了地震环境噪声互相关技术，以估计经验绿色函数之间的接收器。提取的Rayleigh波群速度将与远震Rayleigh波相速度频散曲线进行补充，以提高三维剪切速度模型反演数据集的质量。剪切波速度模型将用于区分盆地中心的先前假设性质，如蛇纹石化、典型的洋壳或底侵物质。特别是，海盆洋壳的几何形状与形成它的主要地球动力学事件的关系特别令人感兴趣。目前的地震活动率是在利古里亚海是适度的4- 4. 5级的事件，大约周期为2-3年。尽管地震活动水平中等，但历史上该地区发生过破坏性地震，如1897年盆地中心的因佩里亚地震（Mw6.3 -7.5），造成至少600人伤亡。LOBSTER OBS网络将允许首次精确确定地震矩释放，具有均匀分辨率，低至小震级事件（Ml 1-2），从而识别活动断层及其与当前盆地开放有关的孕震深度。活动断层的当前位置和性质知之甚少，对当地地震活动性的深入分析将启发利古里亚盆地的浅层地质和可能的应力状态（来自震源机制）。