Collaborative Research: Origin of High Magnetic Remanence in Fault Pseudotachylites

合作研究：断层拟泰石高剩磁的成因

• 批准号: 0228818
• 负责人: Eric Ferre
• 金额: $ 11.05万
• 依托单位: Southern Illinois University at Carbondale
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-01-01 至 2004-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0228818&HistoricalAwards=false
• 关键词: Collaborative; Research; Origin; Magnetic; Remanence

EAR-0228818FerreFrictional heating during coseismic deformation can lead to the melting of the fault rocks and formation of pseudotachylite if slip is important. The increasingly reported existence of earthquake lightning shows that transient coseismic electric currents of large intensity are associated with large magnitude earthquakes (M 6.0). Such currents are likely to follow pseudotachylite veins because their electric conductivity, being melts, is considerably larger than that of the unmolten rocks. All previous and preliminary results on fault-related pseudotachylites show that they have an anomalously high remanent magnetization. Their remanent magnetic properties are similar to those of lightning struck rocks, which suggests that large electric pulses were involved in the magnetization. This project aims at demonstrating that remanence anomalies in pseudotachylites are generally observed and that coseismic electric currents are responsible for it. The investigators propose to test the hypothesis on three young pseudotachylites from seismically active fault zones (California, Japan and Western Alps) by collecting oriented samples for paleomagnetic studies. Samples collected at various points with respect to the main fault plane will enable us to test the coseismic current hypothesis. The geometry and the characteristics of the magnetizing field will be compared with the Earth's magnetic field at the time of pseudotachylite formation. This will provide an independent second test for the coseismic current hypothesis. A series of experiments will generate artificial pseudotachylites using the friction welding method. The artificial and natural pseudotachylites will be compared to assess the possible causes of anomalous magnetization in natural specimens. The direct study of coseismic currents is made difficult by their transient nature. This problem can be circumvented by using the remanent magnetic record of rocks affected by the electrical phenomenon. This research will open new directions of investigation on coseismic electric currents in fault rocks and should contribute to a better understanding of coseismic electric phenomena--

EAR-0228818Ferre 如果滑移很重要，同震变形过程中的摩擦加热可能会导致断层岩石熔化并形成假速岩。越来越多的关于地震闪电存在的报道表明，大强度瞬态同震电流与大地震（M 6.0）有关。这种电流很可能沿着假速石脉流动，因为它们熔化后的电导率比未熔化岩石的电导率大得多。之前所有关于与断层相关的赝速石的初步结果都表明它们具有异常高的剩磁。它们的剩磁特性与雷击岩石相似，这表明磁化涉及大电脉冲。 该项目旨在证明假速石中的剩磁异常是普遍观察到的，并且同震电流是造成这种现象的原因。研究人员提议通过收集用于古地磁研究的定向样本来检验来自地震活跃断层带（加利福尼亚、日本和西阿尔卑斯山）的三种年轻假速石的假设。在主断层面不同点采集的样本将使我们能够检验同震流假设。磁化场的几何形状和特征将与假速石形成时的地球磁场进行比较。这将为同震流假说提供独立的第二次检验。一系列实验将利用摩擦焊接方法生成人造假速石。将比较人造假速石和天然假速石，以评估自然标本中异常磁化的可能原因。同震电流的瞬态性质使得直接研究变得困难。这个问题可以通过利用受电现象影响的岩石的剩磁记录来解决。 这项研究将为断层岩中同震电流的研究开辟新的方向，并有助于更好地理解同震电流现象——