Evolution of the physical, geochemical and mechanical properties of the Alpine Fault Zone: A journey through an active plate boundary

高山断层带物理、地球化学和力学特性的演变：穿越活动板块边界的旅程

• 批准号: NE/J022128/1
• 负责人: Damon Teagle
• 金额: $ 45.58万
• 依托单位: University of Southampton
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2012
• 资助国家: 英国
• 起止时间: 2012 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FJ022128%2F1
• 关键词: Evolution; physical; geochemical; mechanical; properties

This proposal is the UK component of a major international campaign, the Deep Fault Drilling Project (DFDP) to drill a series of holes into the Alpine Fault, New Zealand. The overarching aim of the DFDP to understand better the processes that lead to major earthquakes by taking cores and observing a major continental fault during its build up to a large seismic event. The next stage of this project will be to drill and instrument a 1.5 km hole into the Alpine Fault.Earthquakes are major geohazards. Although scientists can predict where on the Earth's surface earthquakes are most likely to occur, principally along plate boundaries, we have only imperfect knowledge. We also don't know when earthquakes will occur. This is well illustrated by recent events on the South Island of NZ. Two earthquakes in Christchurch in Sept 2010 and Feb 2011 caused 181 deaths and £7-10 billion of damage (~10% NZ GDP). Yet Christchurch had previously been considered of relatively low seismic risk. In contrast, the western side of the South Island is defined by the Southern Alps, a major mountain chain (>3700 m) formed along the Australian-Pacific Plate boundary. Until a few million years ago this plate boundary was a strike-slip fault like the San Andreas Fault in California, but subtle changes in plate motion has led to the collision of the Pacific and Australian Plates. This caused uplift of the mountains and due to very high rates of rainfall and erosion, rapid exhumation of rocks that until recently had been deep within the Earth. Although these plates are moving past each other at ~30 mm/y and the uplift rate in the Southern Alps approaches 10 mm/y, there has not been a major earthquake along the Alpine Fault in NZ's, albeit short, written history. However, there is palaeo-seismic evidence that major earthquakes do occur along the Alpine Fault with magnitude ~8 earthquakes occurring every 200-400 years, with the latest event in 1717 AD.Earthquake occur because stresses build-up within the relatively strong brittle upper crust. At greater depths (>15 km) rocks can flow plastically and plates can move past each other without building up dangerous stresses. On some faults, the brittle crust "creeps" in numerous small micro-earthquake events and this inhibits the build up of stress. Unfortunately there are few even micro-earthquake events along the Alpine Fault or surface evidence for deformation, suggesting that the stresses along this plate boundary have been building up since 1717 - if that stress was released in a single earthquake it would result in a horizontal offset across the fault of >8 m!A major hindrance to earthquake research is a lack of fault rock samples from the depths where stresses build up before an earthquake. Fault rocks exposed at the surface tend to be strongly altered. The strength of fault rocks will depend on a number of factors include pressure, temperature and the nature of the materials, but also whether there are geothermal fluids present. The geometry of the Alpine Fault is special in that the fault rocks that were recently deforming at depth within the crust are exposed close to the surface. Also because of rapid uplift and erosion the local geothermal gradients are high and relatively hot rocks are near the surface. This results in a relatively shallow depth (5-8 km) for the transition from brittle to plastic behaviour. This provides a unique opportunity to drill into the fault zone to recover cores of the fault, to undertake tests of the borehole strata, and to install within the borehole instruments to measure temperature, fluid pressures, and seismic activity. Once core samples are recovered we will perform geochemical and microstructural analyses on the fault rocks to understand the conditions at which they were deformed. We will subject them to geomechanical testing to see how changes in their environment affects the strength of the rocks and their ability to accommodate stresses before breaking.

该提案是一项重大国际运动“深断层钻探项目”(DFDP) 的英国组成部分，该项目旨在在新西兰阿尔卑斯断层上钻一系列孔。DFDP 的总体目标是更好地了解导致大地震的过程。该项目的下一阶段将在阿尔卑斯断层上钻一个 1.5 公里长的孔并用仪器测量。尽管科学家可以预测地球表面最有可能发生地震的地方（主要是板块边界），但我们也不知道地震何时会发生，南方最近发生的事件就很好地说明了这一点。新西兰岛屿。2010 年 9 月和 2011 年 2 月在基督城发生的两次地震造成 181 人死亡，造成 7 至 100 亿英镑的损失（约占新西兰 GDP 的 10%）。相比之下，南岛的西侧被认为是相对较低的地震风险，这是一条沿着澳大利亚-太平洋板块边界形成的主要山脉（> 3700 米）。边界是像加利福尼亚州圣安德烈亚斯断层一样的走滑断层，但板块运动的微妙变化导致了太平洋板块和澳大利亚板块的碰撞，这导致了山脉的隆起，并且由于降雨和侵蚀的速度非常快，快速挖掘尽管这些板块以大约 30 毫米/年的速度相互移动，南阿尔卑斯山的抬升率接近 10 毫米/年，但阿尔卑斯山沿线还没有发生大地震。新西兰的断层历史虽然短暂，但有古地震证据表明，沿阿尔卑斯断层确实发生过大地震，每 200-400 年就会发生一次 8 级地震，最近的一次地震发生在 200-400 年。公元 1717 年。地震的发生是因为在较深的地方（>15 公里），相对坚固的脆性上地壳内积聚了应力，岩石可以塑性流动，并且板块可以相互移动，而不会在某些断层上积聚危险的应力。不幸的是，沿着阿尔卑斯断层的微地震事件或地表变形证据很少，这表明许多小型微地震事件中都存在“蠕变”，这抑制了应力的积累。自 1717 年以来，沿该板块边界的应力一直在累积 - 如果该应力在单次地震中释放，将导致断层上的水平偏移 > 8 m！地震研究的一个主要障碍是缺乏断层岩地震前暴露在地表的断层岩石的应力往往会发生强烈变化，断层岩石的强度取决于许多因素，包括压力、温度和材料的性质，还取决于是否发生变化。存在地热流体。阿尔卑斯断层的几何形状很特殊，因为最近在地壳深处变形的断层岩石暴露在靠近地表的地方，而且由于快速的抬升和侵蚀，局部地温梯度很高，并且相对较热的岩石位于地表附近。这导致从脆性行为到塑性行为的转变的深度相对较浅（5-8公里），这提供了钻探断层带以恢复断层岩心、进行钻孔地层测试和进行钻探的独特机会。安装在钻孔内一旦采集到岩心样本，我们将对断层岩石进行地球化学和微观结构分析，以了解它们变形的条件。我们将对它们进行地质力学测试，以了解断层岩石的变形情况。它们所处的环境会影响岩石的强度及其在破裂前承受应力的能力。

项目成果

Frictional properties and 3-D stress analysis of the southern Alpine Fault, New Zealand

• DOI: 10.1016/j.jsg.2018.06.003
• 发表时间: 2018-09
• 期刊: Journal of Structural Geology
• 影响因子: 3.1
• 作者: C. Boulton;C. Boulton;N. Barth;D. Moore;D. Lockner;John Townend;D. Faulkner

Penetration of Meteoric Fluids to the Seismogenic Zone of the Alpine Fault, New Zealand

大气流体渗透到新西兰高山断层的地震带

• 作者: Catriona Menzies (Author)

Geochemical and microstructural evidence for interseismic changes in fault zone permeability and strength, A lpine F ault, N ew Z ealand

新西兰阿尔卑斯断层断层带渗透性和强度震间变化的地球化学和微观结构证据

• DOI: 10.1002/2016gc006588
• 发表时间: 2017
• 期刊: Geochemistry, Geophysics, Geosystems
• 作者: Boulton C

The Significance of Heat Transport by Shallow Fluid Flow at an Active Plate Boundary: The Southern Alps, New Zealand

活动板块边界处浅层流体流动的热传输意义：新西兰南阿尔卑斯山

• DOI: 10.1029/2018gl078692
• 发表时间: 2018
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Coussens J

Fluid Flux in Fractured Rock of the Alpine Fault Hanging-Wall Determined from Temperature Logs in the DFDP-2B Borehole, New Zealand

根据新西兰 DFDP-2B 钻孔温度测井确定高山断层上盘裂隙岩中的流体通量

• DOI: 10.1029/2017gc007317
• 发表时间: 2018
• 期刊: Geochemistry, Geophysics, Geosystems
• 作者: Janku-Capova L