The evolution of deformation mechanisms, physical conditions and physical properties in the seismogenic Alpine Fault zone: a pilot study

地壳中大型断层的运动由断层岩石的物理性质控制：这些物质形成于断层运动带内。地震发生在地壳顶部10-20公里处(称为地震孕育区)。地震孕育带中的断层岩(脆性断层岩)是由许多小颗粒组成的物质形成的过程，这些小颗粒相互滚动和滑动，流体在这些过程中起着重要的控制作用。了解脆性断层岩石的物理学对于了解断裂在数百万年时间尺度上的长期运动以及理解大地震的成核、破裂和停止都是至关重要的。新西兰阿尔卑斯断裂带是一条主要的板块边界断裂，每隔200-400年就会发生一次大地震。断层运动涉及到很大一部分右行走滑--当一个人站在断层的一侧时，另一侧向右移动(以每年约35毫米的速度移动，以数十万年的平均速度移动)。它还包括反向运动，使东侧向上滑动，并以每年约10毫米的速度滑过西侧。南岛西海岸的降雨量非常大，抬升的物质被迅速侵蚀，因此断层在数万到数百万年的时间里的作用是将物质从深处带到地球表面。从10公里到地表的物质需要一百万年的时间。阿尔卑斯断裂带的独特之处在于，地表的断裂岩来自断裂带的所有深度，相当于今天的活动断裂正在产生的断裂岩。我们可以在地表采集5公里深形成的脆性断层岩样本，我们可以使用地球物理学(地球遥感)来找出在5公里深的活动断层中今天存在的条件，在那里形成了等价的断层岩。没有其他地方我们可以做到这一点。在这项提议中，我们的目标是从阿尔卑斯断裂带收集第一个完整的脆性断层岩段，并利用这些断层岩更好地了解孕震带中的过程物理。脆性断层岩常被河流砾石覆盖，地表没有露出完整的断面。因此，为了收集样本，我们计划钻透大约150米的岩石，并从钻孔中收集岩芯。岩心样本将在实验室进行分析，以便我们了解它们的物理性质，并更好地模拟它们在地震时间尺度和更长时间尺度上的行为。该项目将涉及重大的国际研究合作，并为国际大陆钻探方案支持的更雄心勃勃的深部钻探和相关科学方案提供垫脚石。最终目标是将阿尔卑斯山断裂带作为一个天然的实验室，以了解孕震带岩石变形的物理和地震破裂的物理。

The movement of large faults in the Earth's crust is controlled by the physical properties of the fault rocks: these are materials formed within the zone of fault movement. Earthquakes are generated in the top 10-20 km of the earth's crust (known as the seismogenic zone). The fault rocks in the seismogenic zone (brittle fault rocks) are formed by processes that produce material made up of lots of small particles that roll-around and slide past each other, with fluids playing an important role in controlling these processes. Understanding the physics of brittle fault rocks is crucial to understanding both the long-term movement of faults, on a time scale of millions of years, and to understanding the nucleation, rupture and cessation of large earthquakes. The Alpine Fault zone of New Zealand is a major plate-boundary fault that produces great earthquakes every 200-400 years. The fault movement involves a large component of dextral strike-slip - when one stands on one side of the fault the other side moves to the right (at about 35mm per year averaged over hundreds of thousands of years). It also involves reverse movement, so that the east side is sliding upwards and over the west side, at about 10 mm per year. There is a very-high rainfall on the west coast of the South Island and the uplifted material is eroded quickly so that the action of the fault over tens of thousands to millions of years is to bring materials from depth up to the Earth's surface. Materials from 10km get to the surface in a million years. What is unique about the Alpine Fault zone is that fault rocks at the surface have come from all depths in the fault zone and that equivalent fault rocks are being generated by the active fault today. We can sample brittle fault rocks at the surface that were formed at 5km depth and we can use geophysics (remote sensing into the Earth) to find out about what conditions exist today in the active fault at 5km depth, where equivalent fault rocks are being created. There is nowhere else where we can do this. In this proposal we aim to collect the first complete section of brittle fault rocks from the Alpine Fault zone and to use these to better understand the physics of processes in the seismogenic zone. The brittle fault rocks are often covered by river gravels and no complete section is exposed at the surface. So to collect the samples we plan to drill through about 150m of rock and collect cores from the drill hole. The core samples will be analysed in the laboratory so that we know their physical properties and can model better their behaviour on earthquake timescales and longer timescales. This project will involve significant international research collaboration and provides a stepping stone towards a more ambitious programme of deeper drilling and allied science supported by International Continental Drilling Programme. The ultimate goal is use the Alpine Fault Zone as a natural laboratory to understand the physics of rock deformation in the seismogenic zone and the physics of earthquake rupture.