Measuring aseismic fault slip during a normal faulting earthquake sequence in central Italy

意大利中部的构造断层系统是造成显著破坏性地震的原因-例如M6.3 2009拉奎拉和M6.2 2016阿马特里斯事件-以及可能持续数月甚至数年的复杂地震序列。 控制地震的空间和时间聚集的过程，如在中央意大利序列的情况下，目前只是知之甚少，目前的余震和地震触发模型是不完整的。 目前的模型的缺点是真实的意大利中部，在那里的模型不足以解释地震序列的空间和时间特征。 断层相互作用和地震集群的一种建议机制是，一些断层或断层的部分滑动而不产生地面震动地震波。 在圣安德烈亚斯断层、北安纳托利亚断层和卡斯卡迪亚俯冲带的部分地区，以及世界各地的其他地方，都有人提出过这种行为。 对意大利中部的微地震和断层岩的研究间接支持了这种慢地震滑动假说，但在那里很难直接测量慢地震断层滑动，因为需要专门的仪器来检测与这种事件有关的小振幅和慢速度的地面运动。 我们的项目将部署一个网络的多传感器仪器在浅钻孔能够检测小信号与缓慢的地震断层滑动在意大利中部。 我们收集的新数据将为控制地震和断层的机制提供有价值的新见解，对地震灾害评估以及地震和断层的物理学具有重要意义。 我们部署的钻孔仪器将建立在对地球物理基础设施的重大外国投资的基础上，以利用NSF EarthScope板块边界观测站的剩余仪器来研究东半球意大利断层系统。 由此产生的数据集将解决几个一阶问题：（1）地震断层加载应力在地震倾向的断层上是稳定的还是间歇性的？(2)地震滑动模式与地震断层上或附近的微震活动模式是否相关？(3)地震断层滑动的空间和时间特征，包括滑动幅度、速率、传播方向和速率，以及事件持续时间是什么？ 这些问题直接关系到我们对断层摩擦力、断层力学和地震灾害的理解。 我们收集的数据将为一个新兴的国际合作提供信息，该合作涉及美国研究人员和学生，他们专注于使用意大利中部作为天然实验室的地震断层滑动和地震。 我们将培训一名美国研究生钻孔应变仪分析方法。 对意大利中部地区地震滑动的精确认识将对长期存在的关于自然界中低角度正断层滑动可能性的争论产生影响。 来自钻孔网络和其他地球物理网络的数据将被纳入可解释的国外地球研究（AE）课程。 AE总部位于意大利的奥维多，靠近我们的意大利现场中心。 AE是美国大学学生的一门顶级课程，为地质学野外营地提供了一个残疾人无障碍的替代方案，旨在通过使所有学生尽可能接近地球科学来增加地球科学家之间的多样性。AE的学生将为一个主要的国际研究项目做出贡献。 AE计划是独立资助的，每年夏天将无限期运行，每年为大约8-12名美国学生提供服务，包括残疾学生。该奖项由国际科学与工程办公室共同资助。

The tectonic fault system in central Italy is responsible for notably destructive earthquakes -such as the M6.3 2009 L'Aquila and M6.2 2016 Amatrice events- and complex earthquake sequences that may last for several months or even years. The processes that control the spatial and temporal clustering of earthquakes, as in the case of the central Italy sequences, are currently only poorly understood and current models for aftershocks and earthquake triggering are incomplete. The shortcomings of current models are particularly true for central Italy, where the models inadequately explain the spatial and temporal characteristics of earthquake sequences. One proposed mechanism for fault interaction and earthquake clustering is that some faults or portions of faults slip without producing ground shaking seismic waves. Such behavior has been suggested on portions of the San Andreas fault, the North Anatolia fault, and the Cascadia subduction zone among other locations around the world. Studies of micro-earthquakes and fault rocks in central Italy indirectly support this slow aseismic slip hypothesis, but direct measurement of slow aseismic fault slip has been difficult obtain there, because specialized instrumentation is required to detect the small amplitude and slow speeds of ground motions associated with such events. Our project will deploy a network of multi-sensor instruments in shallow boreholes capable of detecting the small signals associated with slow aseismic fault slip in central Italy. The new data that we collect will provide valuable new insights into the mechanisms that control earthquakes and faulting, with important implications for earthquake hazards assessment and the physics of earthquakes and faulting. The borehole instruments that we deploy will build on significant foreign investments in geophysical infrastructure to study aseismic Italy fault systems, taking advantage of surplus instrumentation from the NSF EarthScope Plate Boundary Observatory. The resulting data sets will address several first order questions: (1) Do aseismic faults load stress on earthquake prone faults steadily or episodically through time? (2) Does the pattern of aseismic slip correlate with the pattern of micro-seismicity on or near aseismic faults? (3) What are the spatial and temporal characteristics of aseismic fault slip, including slip magnitudes, rates, propagation directions and rates, and event durations? These questions bear directly on our understanding of fault friction and mechanics, and earthquake hazards. The data we collect will feed a burgeoning international collaboration involving US researchers and students focused on aseismic fault slip and earthquakes using central Italy as a natural laboratory. We will train a US graduate student in borehole strainmeter analysis methods. Refined understanding of aseismic slip in central Italy will bear on a long-standing debate regarding the possibility of slip on low angle normal faults in nature. Data from the borehole network and other geophysical networks will be incorporated into the Accessible Earth Study Abroad (AE) curriculum. AE is based in Orvieto, Italy, near our field central Italian field site. AE is a capstone course for students at US universities that provides a disability-accessible alternative to geology field camp and aims to increase diversity among geoscientists by making geoscience as accessible as possible to all students. Students of AE will contribute to a major international research program. The AE Program is funded independently and will run every summer indefinitely, serving approximately 8-12 US students each year, including students with disabilities. This award is cofunded by the Office of International Science and Engineering.