Using magnetic responses of natural magnetic systems to quantify geohazards.

利用自然磁系统的磁响应来量化地质灾害。

• 批准号: EP/X02878X/1
• 负责人: Adrian Muxworthy
• 金额: $ 2.06万
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FX02878X%2F1
• 关键词: Using; magnetic; responses; natural; systems

We know that geohazards such as earthquakes and volcanic eruptions, give rise to stresses, that generate measurable instantaneous magnetic signals, which can also be recorded by rocks. However, current accepted theories for how rocks respond to stress state that the stresses associated with these geohazards (~100 MPa) are too low to affect the magnetisation. Controlled laboratory experiments also suggest that these 'low' pressures are sufficient to generate magnetic signals. There is a clear mismatch between theory and observation. We have no accurate working model for the effect of stress on the magnetic response of minerals. If we can quantify the link between changes in stress and changes in rock magnetisations, then we can design valuable new tools for easy detection and monitoring of surface stresses. Why have we no working model for the effects of stress on the magnetic signal of minerals? Historically the effects of the induced pressures on the magnetic signal have been thought too small (< 1000 MPa) to alter or reset existing "stable" magnetic recordings (remanent magnetisations) in all but the most extreme impacts where heating also plays a significant role. For example, the impact crater that "killed the dinosaurs" - Chicxulub - is thought to have experienced pressures in excess of 60,000 MPa, i.e., 1 million times higher than a nuclear explosion. However, I show numerically as part of this proposal, that this assumption is incorrect. Using the latest state-of-the-art numerical micromagnetic model, I demonstrate in the case for support clearly that pressures of only ~200 MPa or lower are sufficient to affect "stable" magnetic recordings. Whilst 200 MPa is still a very high pressure, such pressures are very common in seismically active fault zones. It is the aim of this proposal to bridge this gap in understanding of the effect of stress on magnetic minerals, by experimentally verifying the numerical models. I will do this through a combination of three approaches: 1) extending the micromagnetic modelling which are on the nanometric scale, 2) experimental measurements on bulk samples on the centimetre scale, and 3) to the link the first two approaches together using Quantum Diamond Microscopy (QDM) done on the micron scale. With the new understanding, in the future I will apply for funding to quantify the magnetic signature of earthquakes by: (1) Determining the magnitude of stress-induced magnetic fields that might be used in early warning systems.(2) Developing a protocol for magnetically quantifying the palaeo-stress fields of palaeo-earthquakes.It is the QDM imaging which will be done in Utrecht and is key to the success of this research and for which the PI requests travel money as part of this proposal. These visits to Utrecht will be done as part of my sabbatical year. I plan to visit Utrecht University on a monthly basis for a about a week at a time starting in January 2023 for nine months to work on this project.

我们知道，地震和火山喷发等地质灾害会产生压力，产生可测量的瞬时磁信号，这也可以由岩石记录下来。然而，目前公认的岩石对应力的反应理论认为，与这些地质灾害有关的应力(~100兆帕)太低，不会影响磁化作用。受控的实验室实验也表明，这些“低”压力足以产生磁信号。理论和观察之间存在明显的不匹配。对于应力对矿物磁性响应的影响，我们没有准确的工作模型。如果我们能够量化应力变化和岩石磁化变化之间的联系，那么我们就可以设计出有价值的新工具，方便地检测和监测表面应力。为什么我们没有研究应力对矿物磁性信号影响的工作模型？在历史上，感应压力对磁信号的影响一直被认为太小(&lt；1000兆帕)，不能改变或重置现有的“稳定”磁记录(剩余磁化)，但在最极端的影响中，加热也起着重要作用。例如，“杀死恐龙”的陨石坑--希克苏鲁伯--被认为承受了超过60,000兆帕的压力，即比核爆炸高出100万倍。然而，作为这项提议的一部分，我用数字说明了这一假设是不正确的。使用最新的最先进的微磁数值模型，我在支持的情况下清楚地证明，只有~200兆帕或更低的压力足以影响“稳定的”磁记录。虽然200兆帕仍然是一个很高的压力，但这种压力在地震活跃的断裂带中非常常见。这项建议的目的是通过实验验证数值模型来弥合这一差距，以了解应力对磁性矿物的影响。我将通过三种方法的组合来做到这一点：1)扩展纳米尺度上的微磁建模，2)在厘米尺度上对大量样品进行实验测量，以及3)使用微米尺度上的量子钻石显微镜(QDM)将前两种方法联系在一起。有了新的理解，在未来，我将申请资金，通过以下方式量化地震的磁性特征：(1)确定可能用于早期预警系统的应力感应磁场的大小。(2)开发一种对古地震的古应力场进行磁性量化的协议。这是将在乌得勒支完成的QDM成像，是这项研究成功的关键，PI要求旅行资金作为这项提议的一部分。这些对乌得勒支的访问将作为我休假年的一部分。我计划从2023年1月开始每月访问乌得勒支大学，每次大约一周，为期九个月，以完成这个项目。