Collaborative Research: Space-Based Measurements of Crustal Deformation along the Entire Dead Sea Fault System (Eastern Mediterranean)

本研究利用全球定位系统（GPS）测量，首次对整个死海断层系统的近场应变进行了全面的观察。该断层系统是东地中海地球动力学框架的重要组成部分，它将阿拉伯板块和西奈板块分隔开来，并将红海（亚喀巴湾）的原始海洋扩张与阿拉伯-欧亚碰撞（土耳其南部）联系起来。死海左侧断裂系统横跨800多公里，是世界上最大的大陆转换系统之一。在过去的两个世纪里，不同剖面上大地震的平均复发间隔在500到1100年之间，而且大地震（震级大于7级）的地震很少，因此该断层系统是了解沿缓慢移动（小于10毫米/年）转换断层的地震复发与地壳变形之间关系的绝佳场所。到该项目的第四年，大多数GPS站点（测量和新连续）的1西格玛不确定度将小于0.5 mm/年。由此产生的GPS速度场将为死海断层系统的运动学和地球动力学建模提供基础，这将阐明转换构造的基本方面，以及与地中海东部构造有关的更广泛的问题（例如，西奈和阿拉伯板块的内部变形，死海断层-东安纳托利亚断层-塞浦路斯弧三重结的性质，死海断层的年龄和地质演化）。研究的关键问题包括：1)滑移率在变形过程中的变化及其对现有板块构造模式的启示；2)现今滑动速率与地质估计的比较，对死海断裂系统主要部分的起始时间及其与阿拉伯-欧亚大陆碰撞和红海裂陷的关系具有重要意义；3)断层弯曲和台阶处的滑动传递和应变分配（如黎巴嫩约束弯曲和死海盆地）；4)岩石圈流变对应变沿变换分配的影响。死海断裂系统是世界上主要的大陆转换断裂系统之一。除了阐明东地中海地区的地球动力学方面外，对断层系统的重点研究通常可以深入了解沿大陆转换的构造和地球动力学过程。从构造角度看，死海断裂系统与其他转换断裂系统相比相对简单。结构的简单性使得地震周期和地壳变形过程的建模相对简单，这可以产生与更复杂的断层系统相关的基本见解，例如圣安德烈亚斯断层系统。为此，有足够的大地震的历史和古地震记录，以便沿着死海断层系统的大部分地区进行此类研究。本研究利用高精度GPS测量提供了现今地壳形变的关键约束条件。此外，该项目的结果将直接适用于迫切需要提高对可能早该发生大地震的地区地震危险性的了解。区域地震灾害是大马士革、贝鲁特、安曼、阿勒颇和耶路撒冷等附近大城市的担忧。

This study assembles the first, comprehensive view of near-field strain along the entire Dead Sea fault system using Global Positioning System (GPS) measurements. The fault system, a prominent element of the eastern Mediterranean geodynamic framework, bounds the Arabian and Sinai plates and links proto-oceanic spreading in the Red Sea (Gulf of Aqaba) with the Arabian-Eurasian collision (southern Turkey). Spanning more than 800 km, the left-lateral Dead Sea fault system ranks among the large continental transform systems of the world. With mean recurrence intervals between 500 to 1,100 years for large earthquakes on different sections and a paucity of large (magnitude greater than 7) earthquakes during the past two centuries, the fault system is an excellent locale to understand the relationship between earthquake recurrence and crustal deformation along a slow moving (less than 10 mm/yr) transform fault. By the fourth year of this project, most GPS sites (survey and new continuous) will have 1-sigma uncertainties less than 0.5 mm/yr. The resulting GPS velocity field will provide a basis for kinematic and geodynamic modeling of the Dead Sea fault system that will elucidate fundamental aspects of transform tectonics, as well as broader issues pertaining to eastern Mediterranean tectonics (e.g., internal deformation of the Sinai and Arabian plates, nature of the Dead Sea fault-East Anatolian Fault-Cyprus arc triple junction, age and geological evolution of the Dead Sea fault). Key issues addressed by the research include: 1) variation of slip rates along the transform and the implications about existing plate tectonic models for the region; 2) comparison between present-day slip rates with geological estimates with implications for the timing of initiation of the main parts of the Dead Sea fault system and its relationship to the Arabia-Eurasia collision and Red Sea rifting; 3) slip transfer and strain partitioning at fault bends and step-overs (e.g., the Lebanese restraining bend and the Dead Sea Basin); 4) the influence of lithospheric rheology on strain partitioning along a transform.The Dead Sea fault system ranks among the major continental transform fault systems in the world. In addition to elucidating geodynamic aspects of the eastern Mediterranean region, focused studies on the fault system can yield insight into tectonic and geodynamic processes operating along continental transforms, in general. From a structural perspective, the Dead Sea fault system is relatively simple when compared with other transform fault systems. The structural simplicity permits relatively straightforward modeling of the earthquake cycle and crustal deformation processes, which can yield fundamental insight pertinent to more complicated fault systems, such as the San Andreas fault system. To this end, sufficient historical and palaeoseismic records of large earthquakes exist to facilitate such studies along most of the Dead Sea fault system. This study provides the critical constraints on present-day crustal deformation using high-precision GPS measurements. Additionally, results from this project will be directly applicable for an urgently needed improvement in the understanding of the earthquake hazard in a region that is potentially overdue for a large earthquake. Regional earthquake hazard is a concern for nearby megacities including Damascus, Beirut, Amman, Aleppo, and Jerusalem.