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

基本信息

批准号：
NE/J024449/1
负责人：
Daniel Faulkner
金额：
$ 68.61万
依托单位：
University of Liverpool
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%2FJ024449%2F1
关键词：
Evolution physical geochemical mechanical properties

项目摘要

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% of 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 >8m!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，深层故障钻探项目（DFDP）的英国组成部分，旨在将一系列孔钻入新西兰高山断层。 DFDP的总体目的是更好地了解通过核心并观察到大地震期间的主要连续断层，从而更好地理解导致重大地震的过程。该项目的下一个阶段将是在高山断层中钻和仪器一个1.5公里的孔。地震是主要的地球岩。尽管科学家可以预测地球上最有可能发生的地震发生在哪里，主要是沿板边界发生的，但我们只知道。我们也不知道何时发生地震。最近在新西兰南岛的事件很好地说明了这一点。 2010年9月和2011年2月在基督城举行的两次地震造成了181人死亡，造成了7-100亿英镑的损失（占NZ GDP的10％）。然而，基督城以前被认为具有相对较低的地震风险。相比之下，南岛的西侧是由南阿尔卑斯山（Southern Alps）定义的，南阿尔卑斯山（Southern Alps）是沿澳大利亚太平洋板块边界形成的主要山脉（> 3700 m）。直到几百万年前，这个板块边界一直是加利福尼亚州的圣安德烈亚斯断层等滑滑断层，但板盘运动的细微变化导致了太平洋和澳大利亚板块的碰撞。这引起了山脉的振奋，并且由于降雨和侵蚀的速率很高，直到最近才深入地球深处的岩石爆发。尽管这些盘子以〜30毫米/y的速度互相移动，而南方南方人的升高速度接近10毫米/y，但在新西兰的阿尔卑斯山断层沿线并没有发生重大地震，尽管简短，书面历史。然而，有古老的证据表明，每200 - 400年发生每200 - 400年发生一次沿高山断层发生重大地震，而1717年发生的最新事件发生了earthquake。在更大的深度（> 15公里）的情况下，岩石可以塑料流动，板可以彼此移动而不会产生危险的压力。在某些断层上，在许多小的微观事件中脆弱的地壳“蠕变”，这会抑制压力的积累。不幸的是，沿高山断层或表面变形的表面证据，甚至几乎没有微地夸克事件，这表明自1717年以来，该板界的压力一直在增加 - 如果在一次地震中释放了压力，它将导致水平偏移跨越> 8m> 8m的断层！地震研究的主要障碍物缺乏岩石的压力，即在地球上造成了一定的压力。表面暴露的断层岩石往往会发生强烈改变。断层岩石的强度将取决于许多因素，包括压力，温度和材料的性质，以及是否存在地热流体。高山断层的几何形状是特殊的，因为最近在外壳内深度变形的断层岩石靠近表面。同样，由于迅速的升高和侵蚀，局部地热梯度很高，相对较热的岩石在地面附近。从脆性行为到塑料行为，这导致相对浅深（5-8 km）。这提供了一个独特的机会，可以钻入断层区以恢复断层的核心，进行钻孔地层的测试，并安装在钻孔仪器中，以测量温度，流体压力和地震活动。恢复核心样品后，我们将对断层岩石进行地球化学和微结构分析，以了解它们变形的条件。我们将对它们进行地质力学测试，以了解其环境的变化如何影响岩石的强度及其在破裂之前适应压力的能力。

项目成果

期刊论文数量（10）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

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
通讯作者：
C. Boulton;C. Boulton;N. Barth;D. Moore;D. Lockner;John Townend;D. Faulkner

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