Collaborative Research: Evaluating the Rheological Structure of the North Anatolian Fault Zone, Turkey

合作研究：评估土耳其北安纳托利亚断裂带的流变结构

• 批准号: 1629356
• 负责人: Laurent Montesi
• 金额: $ 12.01万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-08-01 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1629356&HistoricalAwards=false
• 关键词: Collaborative; Research; Evaluating; Rheological; Structure; Collaborative; Research; Evaluating; Rheological; Structure

The main objective of this project is to understand how earthquakes occur along major strike-slip faults, such as the San Andreas fault in California. More specifically, the research team will identify which part of the tectonic plates are the strongest and which ones are the weakest, which can feed into better models of the mechanics of strike-slip faults. To do this, the team will study parts of the North Anatolian Fault zone, a strike-slip fault in Turkey with a geometry very similar to the San Andreas and the site of many destructive earthquakes, such as the 1999 Izmit and Dücze earthquakes and the 2011 Van earthquake. There are two unique attributes of the North Anatolian Fault zone that make it particularly useful for understanding the earthquake cycle and the strength of the plate. First, small pieces of the upper mantle (such rocks are known as xenoliths) are brought up in volcanoes along the fault. These rocks allow for direct evaluation of how the Earth?s mantle, which is thought to be the strongest part of a tectonic plate, is deformed in a strike-slip fault. Second, entire blocks of the middle crust, the other candidate for the strongest part of a tectonic plate, have been brought up along the North Anatolian Fault. Thus, in this region, the team can directly test the relative strengths of the different parts of the tectonic plates in a strike-slip setting. The project will advance desired societal outcomes through training of U.S. graduate students and promote international scientific collaboration. This interdisciplinary project will integrate empirical and theoretical approaches to generate new understanding of lithospheric rheology in strike-slip fault systems. The aim of the project is to study the North Anatolian Fault zone, Turkey, by integrating field investigations, microstructural analysis, and geodynamic modeling. The research team will use a series of unique exposures in the Sea of Marmara region of the North Anatolian Fault zone, to better understand the rheological behavior of the upper mantle and middle crust in the same, active strike-slip fault. First, the researchers will study a series of mantle xenoliths exposed in two volcanic centers along the north margin of the fault system. The mechanical properties, and volatile content of the lithospheric mantle at 45 to 80 km below the surface will be characterized from the xenoliths. Second, the team will characterize lateral variations in finite strain, stress, viscosity, and deformation mechanisms of samples from a mid-crustal exposure that was affected by strike-slip deformation in the North Anatolian Fault zone and was subsequently exhumed. Various rheological models that predict different strength variations with depth will be tested by comparing the mid-crustal to the upper mantle strength. Geodynamic modeling will simulate how the different lithospheric layers interact during the seismic cycle in strike-slip systems, testing specifically whether the brittle fault and ductile layers interact to control the stress level throughout the lithosphere. These models will be evaluated against the stress and deformation conditions estimated from xenoliths and mid-crustal exposures, as well as surface velocities before and after the 1999 Izmit and Dücze earthquakes. By comparing the North Anatolian Fault zone with results from other strike-slip fault systems, this project aims at characterizing the strength of strike-slip systems in general. In particular, it will address if strike-slip fault systems have systematically different characteristics than fault zones in other tectonic environments, and whether a lithosphere feedback between brittle and ductile layers controls the mechanical behavior of strike-slip fault zones. The goal of the project is to produce an accurate understanding of the seismic cycle on active strike-slip fault systems, and hence, the work is relevant to seismic hazards in western Turkey and elsewhere.

该项目的主要目的是了解地震是如何沿着重大滑移断层发生的，例如加利福尼亚州的圣安德烈亚斯断层。更具体地说，研究团队将确定构造板的哪一部分是强的，哪些是最弱的，哪些可以进一步发展为更高的走滑断层力学模型。为此，团队将研究北安纳托利亚断层区域的一部分，这是土耳其的一次滑滑断层，几何形状与圣安德烈亚斯和许多破坏性地震的地点非常相似，例如1999年的伊兹米特和dücze地震和2011年的范·地震。北安纳托利亚断层区有两个独特的属性，使其对于理解地震周期和板的强度特别有用。首先，上地幔的小块（这种岩石被称为异种石）在断层沿火山堆积。这些岩石允许直接评估地球的地幔（认为是构造板的强部分）如何在走滑断层中变形。其次，沿着北部的安纳托利亚断层抬起了整个地壳的整个块，是构造板块强的另一个候选者。在这一地区，团队可以直接测试滑滑环境中构造板的不同部位的相对强度。该项目将通过培训美国研究生并促进国际科学合作来提高期望的社会成果。这个跨学科的项目将整合经验和理论方法，以在走滑断层系统中对岩石圈流变学产生新的理解。该项目的目的是通过整合现场调查，微观结构分析和地球动力学建模来研究北安纳托利亚断层区，土耳其。研究小组将在北安纳托利亚断层区的马尔马拉地区使用一系列独特的暴露，以更好地了解上地幔和中地壳的流变行为，同样具有主动滑滑断层。首先，研究人员将研究一系列在断层系统北边缘的两个火山中心中暴露于两个火山中心的地幔异种石。岩石圈地面以下45至80 km的机械性能和挥发性含量将以异种石的特征。其次，该团队将表征有限应变，应力，粘度，粘度和变形机制的横向变化，该样品的中期暴露受到样品的影响，该样品受到北安纳托利亚断层区的行进滑滑变形影响，随后被挖掘出来。通过比较中壳强度，将测试各种预测与深度不同强度变化不同的流变学模型。地球动力学建模将模拟在滑滑系统中的地震周期中不同岩石圈层如何相互作用，从而特别测试了脆性断层和延性层是否相互作用以控制整个岩石圈的应力水平。这些模型将针对从异种石和中期暴露估计的应力和变形条件进行评估，以及1999年Izmit和DüczeEarth Quakes之前和之后的表面速度。通过将北安纳托利亚断层区与其他走滑断层系统的结果进行比较，该项目旨在表征一般而言滑滑系统的强度。特别是，它将解决滑雪断层系统在其他构造环境中具有系统不同的特性，以及在脆性和延性层之间的岩石圈反馈是否控制着滑滑断层区的机械行为。该项目的目的是对主动滑移断层系统上的地震周期进行准确的了解，因此，该工作与土耳其西部和其他地方的地震危害有关。