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、罕见和意想不到的地震压倒了减灾措施和社会应对能力，导致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止地震破裂传播。该项目是与中国研究人员密切合作开展的，将对中国阿尔金断层（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察与数值破裂模拟相结合，以预测沿主要陆内走滑断层沿着的潜在地震规模范围。这项研究的结果将成为评估罕见、异常大事件发生可能性的一种手段。该项目将通过以下方式推进预期的社会成果：（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理解，改善社会中个人的福祉;（3）通过培训研究生和本科生，发展多元化的、具有全球竞争力的STEM劳动力;以及（4）通过与中国科学家的强有力的国际合作和为学生提供国际研究经验来加强伙伴关系。该项目得到了构造学计划和美国国家科学基金会国际科学与工程计划的支持。该研究项目将开发和应用技术，将断层几何学，运动学，和滑动行为与数值破裂模拟，以预测潜在的地震规模的范围沿着中央阿尔金断层超过长度（800公里），远远超过最长的记录大陆走向-滑动地震（420-450 km）。中央阿尔金断层被分为四个限制性的双弯段（阿克赛，平顶山，Akato Tagh和Sulamu Tagh），每个都假设，基于它们的几何形状，阻止大多数，但不是所有的地震破裂。多周期自发动态破裂模型表明，这些地震门可能是打开或关闭的破裂传播的特定方向取决于断层的几何形状和应力条件继承自以前的地震。先前的研究表明，动态破裂效应（由地震波从破裂前传播）和地震间应力松弛（断层外变形）都有助于地质测试模式的沿走向地震滑动和累积滑动率梯度。该项目将把这些破裂模型和地质测试应用于平顶山双约束弯曲，该弯曲似乎是阿尔金断裂沿着相对新生的构造。一个彻底的现场活动将收集新的滑动速率，每事件滑动，断层运动学和结构数据，以约束平顶山约束双弯曲的多周期破裂模型。将开发耦合中央阿尔金断层的所有四个主要约束双弯的模型，并将研究该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.