Collaborative Research: Physical properties of the Alpine Fault, New Zealand: Mechanical and hydrological processes in the brittle fault core and surrounding damage zone

合作研究：新西兰阿尔卑斯断层的物理特性：脆性断层核心及周围损伤区的机械和水文过程

• 批准号: 1215856
• 负责人: Demian Saffer
• 金额: $ 31.6万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1215856&HistoricalAwards=false
• 关键词: Collaborative; Research; Physical; properties; Alpine

Scientists have long known that most large, destructive earthquakes are caused by the slow buildup of stress on fault zones at the boundaries between tectonic plates. Friction between the two sides of the fault holds it together and prevents slip while stress accumulates until the point of failure, precipitating the earthquake itself. However, the nature of how and why that failure occurs and grows into a large earthquake remains poorly understood. It is thought to be governed in large part by the materials that make up the fault zone ? the rock that is fractured and broken down by past earthquakes and the water that fills pore spaces in that rock, as well as the tectonic stresses at the depth of earthquakes. To further our understanding of how faults work, an international team of scientists is conducting a 3-stage project to drill into New Zealand?s Alpine Fault, a major fault zone similar to the San Andreas of California, with a history of magnitude 7-8 earthquakes, and future potential for more. Drilling into the Alpine Fault will provide fresh samples from the fault zone unaltered by the negative effects of earth-surface weathering and erosion. The first stage, already drilled to 150 meters depth, obtained core samples across the fault zone and made measurements of the rock properties made by instruments placed down the holes. In the next stage, one or more holes will be drilled to more than 1500 meters depth, and is intended to sample across the fault at earthquake depths. As part of that effort, the University of Wisconsin-Madison and Penn State University partnership will measure a range of properties of these samples, including their strength (friction-based resistance to slip and the capacity to store up strain without breaking), permeability to pore water movement, and the speeds with which they transmit two types of seismic waves (a widely used way to measure rock properties remotely) under realistic conditions. Furthermore, instruments lowered down the drill holes will be used to measure similar and additional properties at a broader scale. Using the results of sample and the drillhole data, the investigators will evaluate competing hypotheses for the strength of fault zones and the conditions therein, helping discover what happens inside faults between earthquakes, and how they may change leading up to future seismic activity. They will also evaluate the nature of groundwater flow (or lack thereof) in and around the fault zone at depth, important for understanding the pressure and temperature conditions during fault activity. This research, when combined with the complementary work by New Zealand-based collaborators and others, will yield a new understanding of how fault zones work and why earthquakes happen in the ways that they do. It will likely also yield new clues to understanding the future earthquake hazard on the Alpine Fault in particular and on major faults in general.

长期以来，科学家们知道，大多数大型破坏性地震是由于构造板之间边界处的断层区域上压力缓慢而引起的。断层两侧之间的摩擦将其融合在一起并防止滑动，而应力会积聚直到失败点，从而促成地震本身。但是，这种失败的发生方式和原因的性质仍然是众所周知的大地震。人们认为它在很大程度上由构成断层区的材料支配？过去的地震和填充岩石中孔隙空间的水以及地震深度处的构造应力。为了进一步了解过失的工作方式，一个国际科学家团队正在进行一个三阶段的项目，以钻入新西兰的高山断层，这是一个与加利福尼亚州圣安德烈亚斯类似的主要断层区，具有7-8个地震史，未来的潜力以及更多的潜力。钻入高山断层将提供新鲜的样品，这些样品不改变地面风化和侵蚀的负面影响。第一阶段已经钻了到150米的深度，在整个断层区域获得了核心样品，并对孔的岩石特性进行了测量。在下一个阶段，将钻一个或多个孔，深度超过1500米，并旨在在地震深度的断层中进行采样。作为这项努力的一部分，威斯康星大学麦迪逊分校和宾夕法尼亚州立大学的合作伙伴关系将衡量这些样品的一系列特性，包括它们的强度（基于摩擦的耐药性和在不破坏孔隙水的情况下储存压力的能力），孔隙水运动的渗透性以及速度的速度以及两种类型的速度（一种广泛使用的地震范围），以衡量岩石属性不足。此外，降低钻孔的仪器将用于在更广泛的规模上测量相似和其他特性。使用样品和钻孔数据的结果，研究人员将评估断层区域及其条件强度的竞争假设，从而帮助发现地震之间的断层内部发生的事情，以及如何改变导致未来地震活动的变化。他们还将在断层区域内和周围评估地下水流的性质（或缺乏其流量），这对于理解断层活动期间的压力和温度条件很重要。这项研究与新西兰的合作者和其他人的补充工作结合在一起，将对故障区域的工作方式以及为何以其方式进行地震进行新的理解。它可能还会产生新的线索，以了解阿尔卑斯断层，尤其是主要断层的未来地震危害。