Using magnetic responses of natural magnetic systems to quantify geohazards.

我们知道，地震和火山爆发等地质灾害会产生压力，从而产生可测量的瞬时磁信号，这些信号也可以被岩石记录下来。然而，目前公认的关于岩石如何响应应力的理论表明，与这些地质灾害相关的应力（~100 MPa）太低，不会影响磁化。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。对于应力对矿物磁响应的影响，我们还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，以便于检测和监测地表应力。为什么我们没有一个有效的模型来解释应力对矿物磁信号的影响？从历史上看，感应压力对磁信号的影响被认为太小（< 1000兆帕），无法改变或重置现有的“稳定”磁记录（残余磁化），除了最极端的影响，其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——被认为经历了超过60000兆帕的压力，即比核爆炸高100万倍。然而，作为这个建议的一部分，我用数字表明这个假设是不正确的。使用最先进的数值微磁模型，我在案例中清楚地证明了仅~200 MPa或更低的压力就足以影响“稳定”的磁记录。虽然200mpa仍然是非常高的压力，但这样的压力在地震活跃断裂带中是非常常见的。通过实验验证数值模型，本建议的目的是弥合在理解应力对磁性矿物影响方面的这一差距。我将通过三种方法的结合来做到这一点：1)扩展纳米尺度上的微磁建模，2)厘米尺度上的散装样品的实验测量，以及3)在微米尺度上使用量子金刚石显微镜（QDM）将前两种方法联系在一起。有了新的认识，未来我将申请资金，通过以下方式量化地震的磁特征：(1)确定可能用于预警系统的应力诱发磁场的大小。(2)建立了古地震古应力场的磁量化方案。QDM成像将在乌得勒支完成，这是这项研究成功的关键，PI要求旅费作为该提案的一部分。乌得勒支之旅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，每次约一周，为期9个月，从事这个项目。

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.