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的反应能力，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，本研究校准了断层的几何复杂性如何有效地阻碍地震破裂传播。该项目与中国研究人员密切合作，将中国阿尔金断层（地球上最长的活动走滑断层之一）的断层几何形状和滑动行为的实地观测与数值破裂模拟相结合，以预测沿大陆内主要走滑断层的潜在地震规模范围。这项研究的结果将是评估罕见的、不寻常的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民族充分参与STEM；(2)通过对地震破裂过程的新认识，提高了社会个体的幸福感；(3)通过培养研究生和本科生，培养一支多元化、具有全球竞争力的STEM劳动力队伍；(4)通过与中国科学家的强有力的国际合作和学生的国际研究经验，增加伙伴关系。该项目由构造学计划和NSF国际科学与工程计划支持。该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实地观测与数值破裂模拟相结合，以预测沿阿尔金塔赫断层中部800公里(远远超过有记录的最长大陆走滑地震（420-450公里）的潜在地震规模范围。中央的Altyn Tagh断层被四个抑制的双弯（Aksay, Pingding Shan， Akato Tagh和Sulamu Tagh）划分为几段，每个弯曲都是基于它们的几何形状假设的，可以阻止大多数地震破裂，但不是所有地震破裂。多周期自发动力破裂模型表明，这些地震闸门可能会根据断层几何形状和先前地震继承的应力条件向特定的破裂传播方向打开或关闭。先前的研究表明，动态破裂效应（由破裂前沿的地震波传播引起）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率梯度的地质可测试模式。本项目将把这些断裂模型和地质试验应用于平顶山双约束弯曲，这是一个沿阿尔金塔格断层相对新生的构造。全面的现场活动将收集新的滑动率、滑动次数、断层运动学和结构数据，以约束平顶山抑制双弯曲的多旋回破裂模型。研究人员将开发模型，将阿尔金塔赫断层中心的所有四个主要抑制双弯曲结合起来，并研究这个地质校准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.