Spatio-temporal variations of slip on active norma faults in central and southern mainland Greece

希腊大陆中部和南部活动诺玛断层滑动的时空变化

• 批准号: 2547089
• 金额: --
• 依托单位: Birkbeck, University of London
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2547089
• 关键词: Spatio; temporal; variations; slip; active

Understanding how earthquakes occur in space and time has been a complex problem. Two key problems in earthquake forecasting are unpredictable earthquake recurrence times and unpredictable size of earthquakes. The lack of understanding of these issues have resulted in destructive consequences when earthquakes do occur. The problems may remain unsolvable but we can start to improve the understanding of seismic hazard by investigating several factors, such as, fault location, geometry, kinematics, multi-millennia slip-rate histories and strain-rate of fault arrays. The factors are important and should be considered in assessing seismic hazard as they address the following. (a) Fault geometry may relate to rupture kinematics associated with earthquakes. Analysis of the fault geometry and kinematics may help describe the style of ruptures and potentially explain how earthquakes migrate. (b) multi-millennia slip-rate histories analyse time periods long enough to identify multiple earthquakes on faults and identify patterns; clustering and quiescence. (c) Strain-rates of fault arrays reveal how the total combined earthquakes or strain over the multi-millennia timescale is distributed across regions.Greece is a perfect natural laboratory for studying these factors as the country contains a complex network of active faults. The combination of large structures in the form of the Hellenic trench subduction zone and the North Anatolian strike-slip fault have resulted in early stage rifting processes which have produced several differently orientated normal fault arrays. These normal faults frequently show activity in the form of earthquakes which are felt as the crust stretches with destructive earthquakes (Ms ~ 6.0 or greater) occurring approximately once a decade.The overall aim of the PhD project is to investigate different spatial scales from single faults to entire fault arrays whilst incorporating temporal aspects to help reveal the importance of millennia-scale earthquake clustering and quiescence. This will be undertaken by assessing the factors mentioned above; fault location; geometry; kinematics; multi-millennia slip-rate histories; and strain-rate of fault arrays. Generally, the project will include analysis of a specific example of a historic earthquake sequence and the production of a suite of strain-rate maps for multiple fault arrays. (Part 1) Initially, a local spatial investigation of two faults, which have ruptured during a historic earthquake sequence, will be undertaken to analyse the role that fault geometry may have on controlling the rupture style. (Part 2) An accompanying temporal study will be undertaken in the form of 36Cl cosmogenic nuclide-derived fault slip histories of the two faults which will be compared in an attempt to understand how or if the proximal faults relate in terms of their slip histories. (Part 3) The strain-rate mapping will be a temporal and spatial investigation at the scales of entire fault arrays with the aim of displaying the regional distributions of Holocene earthquake activity. The Holocene strain-rates will also be compared to published historical strain-rates to show that seismic hazard varies spatially on different time scales.Studying the temporal and spatial activity of faults will have an important impact on improving seismic hazard analysis and refining earthquake forecasting. Greece is a suitable location for studying faulting due to the complex tectonic setting and frequent earthquake activity. Greek faults have been studied, however, more extensive field data are required in order to help constrain the factors (fault location, geometry, kinematics, multi-millenia slip-rate histories and strain-rate of fault arrays) in central mainland Greece and therefore, improve the understanding of tectonic processes and seismic hazard.

了解地震是如何在空间和时间上发生的一直是一个复杂的问题。地震预报的两个关键问题是地震复发时间的不可预测和地震规模的不可预测。由于对这些问题缺乏了解，当地震发生时就会造成破坏性的后果。这些问题可能仍然无法解决，但我们可以通过研究几个因素，如断层位置、几何形状、运动学、断层阵列的几千年滑动率历史和应变率，开始提高对地震危害的理解。这些因素很重要，在评估地震危险时应予以考虑，因为它们涉及以下内容。(a)断层几何形状可能与与地震有关的破裂运动学有关。对断层几何形状和运动学的分析可能有助于描述断裂的类型，并可能解释地震是如何迁移的。(b)几千年的滑动率历史分析足够长的时间周期，以确定断层上的多次地震和确定模式；群集和静止。(c)断层阵列的应变率揭示了几千年时间尺度上总的地震或应变是如何分布在各地区的。希腊是研究这些因素的完美天然实验室，因为该国拥有复杂的活动断层网络。以希腊海沟俯冲带和北安那托利亚走滑断层形式出现的大型构造的组合导致了早期的裂陷作用，并产生了几个不同方位的正断层阵列。这些正断层经常以地震的形式表现出活动，当地壳伸展时，人们会感觉到破坏性地震（Ms ~ 6.0或更大）大约每十年发生一次。博士项目的总体目标是研究从单个断层到整个断层阵列的不同空间尺度，同时结合时间方面来帮助揭示千年尺度地震聚集和静止的重要性。这将通过评估上述因素来进行；故障定位;几何;运动学;几千年的滑动率历史；以及故障阵列的应变率。一般来说，该项目将包括分析一个历史地震序列的具体例子，并为多个断层阵列制作一套应变率图。（第一部分）首先，将对在历史地震序列中破裂的两条断层进行局部空间调查，以分析断层几何形状在控制破裂方式方面可能发挥的作用。（第二部分）将以36Cl宇宙核素衍生的两条断层滑动历史的形式进行伴随的时间研究，并将其进行比较，以试图了解近端断层在滑动历史方面如何或是否相关。（第三部分）应变率制图将是在整个断层阵列尺度上的时空调查，目的是显示全新世地震活动的区域分布。全新世应变率还将与已公布的历史应变率进行比较，以显示地震危险性在不同时间尺度上的空间变化。研究断层的时空活动性对提高地震危险性分析和改进地震预报具有重要意义。希腊由于其复杂的构造环境和频繁的地震活动，是研究断裂的合适地点。希腊断层已经被研究过，然而，为了帮助约束希腊中部大陆的因素（断层位置、几何形状、运动学、数千年滑动率历史和断层阵列的应变率），从而提高对构造过程和地震危险性的理解，还需要更广泛的现场数据。