Quantification of Unsteady Fault Slip and Fold Growth, Apennine Front, Italy

意大利亚平宁锋面不稳定断层滑动和褶皱生长的量化

• 批准号: 0809722
• 负责人: David Anastasio
• 金额: $ 30.26万
• 依托单位: Lehigh University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-15 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0809722&HistoricalAwards=false
• 关键词: Quantification; Unsteady; Fault; Slip; Fold

This research group proposes that blind thrust faults in the core of growing anticlines exhibit variable slip at 10,000 to 100,000 year time scales and that this slip is rooted in crustal-scale processes of stress transfer among faults responding to climatically-driven processes at the Earth?s surface. Studies along the mountain front of the northern Apennines, Italy will delineate the slip history of two related, but physically disconnected faults at a approximately 20,000 year resolution over a five million year Pliocene - Recent time span. Because this record of fault slip coincides with the well-known large amplitude oscillations in global climate that contribute to the filling and deformation of the Po foreland, the team further hypothesizes that the 100,000 year, and potentially 40,000 year climatic cycles will be reflected in observed slip rates as faults are differentially lubricated by changing ground water conditions, sea-level and structural emergence, and differentially loading by the redistribution of sediment at the surface. The project will employ cyclostraigraphy of anhysteretic remanent magnetization calibrated to accurate models of Earth's orbital motions, which constitutes a high-resolution metronome with a precision, accuracy and continuity that outperforms modern radioisotope geochronology, magnetostratigraphy, and biostratigraphy and transcends the problems of resolution and length of record that have limited GPS and paleoseismic approaches. Fault slip unsteadiness with a periodicity in line with known climatic cycles at 40,000-100,000 year time spans will prove the hypothesis.Knowledge of fault slip rate variation on a fault with 10,000-100,000 year resolution has important geodynamic, and seismic hazard implications particularly for the case of blind thrust faults that can generate significant earthquakes, such as the 2008 Los Angeles basin earthquakes. Similar kinds of earthquakes resulting from blind thrust faults are well documented for the northern Apennine (Italy) mountain front, home to 4 million residents where deformation rates and seismic hazards remain poorly defined. Here spatial and temporal gaps in earthquake activity are considered as places where damaging earthquakes do not or will not occur. This research suggests that such gaps are simply the result of fault slip unsteadiness and aims to determine a cause for the unsteadiness by studying the geologic record.

该研究小组提出，生长背斜核心的隐伏逆冲断层在1万到10万年的时间尺度上表现出可变的滑动，这种滑动源于地壳尺度的断层之间的应力传递过程，这些过程响应于地球表面气候驱动的过程？S。沿着意大利亚平宁北部山前的研究将描绘出两个相互关联但物理上不相连的断层的滑动历史，分辨率约为2万年，跨越500万年的上新世-最近的时间跨度。由于这种断层滑动的记录与众所周知的全球气候的大幅度振荡相吻合，这种大幅度振荡导致了Po前陆的充填和变形，该团队进一步假设，10万年和潜在的4万年的气候周期将反映在观测到的滑动速率中，因为断层因地下水条件的变化、海平面和构造的出现而受到不同的润滑，并通过地表沉积物的重新分布而受到不同的负载。该项目将采用磁滞剩余磁化的循环直线照相术，并根据地球轨道运动的准确模型进行校准，这构成了一个高分辨率节拍器，其精度、准确度和连续性优于现代放射性同位素地质年代学、磁地层学和生物地层学，并超越了限制全球定位系统和古震方法的分辨率和记录长度问题。断层滑动不稳定性具有与已知气候周期一致的周期性，时间跨度为40,000-100,000年，这将证明这一假设。断层上10,000-10,000年分辨率的断层滑动速率变化的知识具有重要的地球动力学和地震危险性，特别是对于可能产生重大地震的盲目逆冲断层的情况，如2008年洛杉矶盆地地震。由盲目的逆冲断层引起的类似类型的地震在(意大利)亚平宁北部山前得到了很好的记录，那里有400万居民，那里的变形率和地震危险仍然没有得到很好的界定。在这里，地震活动的空间和时间间隔被认为是破坏性地震不发生或不会发生的地方。这项研究认为，这些空区只是断层滑动失稳的结果，目的是通过研究地质记录来确定失稳的原因。