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

测量意大利中部正常断层地震序列期间的抗震断层滑移

• 批准号: 1723045
• 负责人: Richard Bennett
• 金额: $ 52.32万
• 依托单位: University of Arizona
• 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: 2017-07-15 至 2024-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1723045&HistoricalAwards=false
• 关键词: Measuring; aseismic; fault; slip; during

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.

意大利中部的构造断层系统造成了尤其是破坏性地震 - 例如M6.3 2009 L'Aquila和M6.2 2016 Amatrice Events and Compecial Eartquake序列，可能会持续数月甚至几年。 与意大利中央序列一样，控制地震的空间和时间聚类的过程仅对余震和余震和地震触发的当前模型不完整，这是不完整的。 当前模型的缺点对于意大利中部尤其如此，在那里模型不足地解释了地震序列的空间和时间特征。 断层相互作用和地震聚类的一种提议的机制是，某些断层或部分断层滑动而不会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其他地区的Cascadia俯冲带中提出了这种行为。 对意大利中部中部的微地Quake和断层岩石的研究间接支持了这种缓慢的无性滑动假说，但是在那里很难直接测量缓慢的无性断层滑移，因为需要专门的仪器来检测与此类事件相关的地面运动的较小振幅和慢速的地面运动。 我们的项目将在意大利中部的浅钻孔中部署一个浅孔中的多传感器仪器网络。 我们收集的新数据将为控制地震和断层的机制提供宝贵的新见解，对地震危害评估以及地震和断层物理学的重要意义。 我们部署的钻孔仪器将基于地球物理基础设施的重大投资，以利用来自NSF Earthscope板边界观测站的剩余仪器来研究意大利断层系统。 所得数据集将解决几个一阶问题：（1）在随着时间的推移会稳定或情节地稳定或情节地对地震易于地震负载压力？ （2）ASEOSIC滑动的模式是否与Aseasis抗性断层或附近的微观性模式相关？ （3）ASESIST断层滑动的空间和时间特征是什么，包括滑动幅度，速率，繁殖方向和速率以及事件持续时间？ 这些问题直接取决于我们对断层摩擦和力学以及地震危害的理解。 我们收集的数据将提供一项新兴的国际合作，涉及美国研究人员和专注于使用意大利中部作为天然实验室的无性断层滑移和地震。 我们将培训一名美国研究生的井孔应力表分析方法。 对意大利中部的无性滑移的精致理解将在长期以来就在自然界中的低角度正常断层上滑动的可能性进行辩论。 来自钻孔网络和其他地球物理网络的数据将纳入国外可访问的地球学习（AE）课程中。 AE总部位于意大利的奥尔维托，附近是意大利中部田间现场。 AE是美国大学的学生的顶峰课程，为地质野营提供了令人难以置信的替代方案，旨在通过使所有学生尽可能访问地球科学来提高地球科学家之间的多样性。 AE的学生将为一项主要的国际研究计划做出贡献。 AE计划是独立资助的，每年夏天将无限期地运行，每年约8-12名美国学生，包括残疾学生。该奖项由国际科学与工程办公室授予。