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

地壳中大断层的运动是由断层岩石的物理性质控制的：这些岩石是在断层运动带内形成的物质。地震发生在地壳顶部10-20公里处（称为发震带）。发震带的断层岩（脆性断层岩）是由大量小颗粒相互滚动和滑动形成的，流体在控制这些过程中起着重要作用。了解脆性断层岩石的物理性质，对于理解断层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、破裂和停止至关重要。新西兰的高山断裂带是一个主要的板块边界断层，每200-400年产生一次大地震。断层运动包含了很大一部分的右走滑——当一个人站在断层的一边时，另一边就会向右移动（数十万年来平均每年约35毫米）。它还涉及反向运动，因此东侧向上滑动并超过西侧，每年约10毫米。南岛西海岸的降雨量非常大，抬升的物质被迅速侵蚀，因此断层的作用在数万到数百万年的时间里将物质从深处带到地球表面。10公里外的物质需要100万年才能到达地表。阿尔卑斯断裂带的独特之处在于，表面的断层岩来自断裂带的各个深处，而今天的活动断层也在产生相同的断层岩。我们可以对地表5公里深处形成的脆性断层岩石进行取样，我们可以使用地球物理（遥感到地球）来找出5公里深处活动断层中目前存在的条件，在那里等效的断层岩石正在形成。我们没有其他地方可以这样做。在这一建议中，我们的目标是收集来自阿尔卑斯断裂带的第一个完整的脆性断层岩石剖面，并利用这些岩石更好地了解孕震带的物理过程。脆性断层岩常被河卵石覆盖，地表未露出完整剖面。因此，为了收集样本，我们计划钻穿大约150米的岩石并从钻孔中收集岩心。这些岩心样本将在实验室里进行分析，这样我们就能知道它们的物理性质，并且可以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。该项目将涉及重要的国际研究合作，并为国际大陆钻探计划支持的更雄心勃勃的深层钻探和相关科学计划提供踏脚石。最终目的是利用高寒断裂带作为一个自然实验室，了解发震区岩石变形的物理规律和地震破裂的物理规律。

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.