Collaborative Research: Earthquake Gates: Linking Earthquake Rupture Length to the Dynamics of Restraining Double Bends on the Altyn Tagh Fault

断层破裂的长度通常控制着大地震的震级。异常大的、罕见的和意想不到的地震压倒了缓解措施和社会应对能力，导致了一连串的灾难性影响。为了评估这种罕见事件的可能性，这项研究校准了断层的几何复杂性如何有效地阻止地震破裂的传播。该项目与中国研究人员密切合作，将对地球上最长的活动走滑断裂之一中国阿尔金断裂的断层几何和滑动行为的现场观测与数值破裂模拟相结合，以预测陆内走滑断裂沿线的潜在地震大小范围。这项研究的结果将是评估罕见、异常重大事件的可能性的一种手段。该项目将通过以下方式促进预期的社会成果：(1)妇女和代表性不足的少数群体充分参与STEM；(2)通过对地震破裂过程的新认识，改善社会个人的福祉；(3)通过培训研究生和本科生，发展一支具有全球竞争力的多样化的STEM劳动力队伍；以及(4)通过与中国科学家的强有力的国际合作，以及通过为学生提供国际研究经验，增加伙伴关系。该项目由构造计划和NSF的国际科学与工程计划支持。研究项目将开发和应用技术，将断层几何、运动学和滑动行为的现场观测与数值破裂模拟相结合，以预测阿尔金断裂中部的潜在地震范围，其长度(800公里)远远超过有记录以来最长的大陆走滑地震(420-450公里)。阿尔金断裂带中部由四个限制性双弯(Aksay、平顶山、Akato Tagh和Sulamu Tagh)分成多个分段，根据它们的几何形状，每个断裂带都被假设为阻止大多数但不是所有地震破裂。多周期自发动态破裂模型表明，这些地震门可能对破裂传播的特定方向开放或关闭，这取决于断层几何形状和从先前地震继承的应力条件。以往的研究表明，动态破裂效应(来自破裂前沿的地震波传播)和震间应力松弛(断层外变形)都有助于形成沿走向地震滑动和累积滑动速率梯度的地质可测试模式。该项目将把这些破裂模型和地质试验应用于平顶山双重约束弯曲，它似乎是阿尔金断裂沿线的一个相对年轻的构造。一场彻底的野外活动将收集新的滑动速率、每事件滑动、断层运动学和构造数据，以约束平顶山约束双弯的多旋回破裂模式。将开发连接阿尔金断裂中部所有四个主要约束双弯的模型，并将研究这个经过地质校准的模型系统的整体行为，以确定罕见的、异常长的地震破裂的可能性。

The length of a fault rupture generally controls the magnitude of a large earthquake. Unusually large, rare, and unexpected earthquakes overwhelm mitigation measures and the societal capacity to respond, leading to a cascade of disastrous effects. In order to assess the potential for such rare events, this study calibrates how effectively geometrical complexities of a fault impede earthquake rupture propagation. The project, carried out in close collaboration with Chinese researchers, integrates field observations of fault geometry and slip behavior of the Altyn Tagh fault in China, one of the longest active strike-slip faults on Earth, with numerical rupture simulations to predict the range of potential earthquake sizes along a major intracontinental strike-slip fault. The outcome of this research will be a means to assess the likelihood of rare, unusually large events. The project will advance desired societal outcomes through: (1) full participation of women and underrepresented minorities in STEM; (2) improved well-being of individuals in society through a new understanding of earthquake rupture processes; (3) development of a diverse, globally competitive STEM workforce through training of graduate and undergraduate students; and (4) increased partnerships through a strong international collaboration with Chinese scientists and international research experiences for students. The project is supported by the Tectonics Program and NSF's International Science and Engineering program.The research project will develop and apply techniques to integrate field observations of fault geometry, kinematics, and slip behavior with numerical rupture simulations to predict the range of potential earthquake sizes along the central Altyn Tagh fault over a length (800 km) that well exceeds the longest recorded continental strike-slip earthquake (420-450 km). The central Altyn Tagh fault fault is divided into segments by four restraining double bends (Aksay, Pingding Shan, Akato Tagh, and Sulamu Tagh) that are each hypothesized, based on their geometry, to stop most, but not all earthquake ruptures. Multi-cycle spontaneous dynamic rupture models show that these earthquake gates may be open or closed to a particular direction of rupture propagation depending upon fault geometry and stress conditions inherited from prior earthquakes. Prior research showed that dynamic rupture effects (resulting from seismic wave propagation from the rupture front) and interseismic stress relaxation (off-fault deformation) both contribute to geologically testable patterns of along-strike earthquake slip and cumulative slip-rate gradients. This project will apply these rupture models and geologic tests to the Pingding Shan double restraining bend, which appears to be a relatively nascent structure along the Altyn Tagh fault. A thorough field campaign will collect new slip rate, slip-per-event, fault kinematic, and structural data to constrain a multi-cycle rupture model for the Pingding Shan restraining double bend. Models will be developed that couple all four of the major restraining double bends of the central Altyn Tagh fault, and the ensemble behavior of this geologically-calibrated model system will be investigated to determine the likelihood of rare, exceptionally long earthquake ruptures.