Development of 2-Dimensional ESR thermal imaging apparatus and its application to drill core samples collected from a subduction seismogenic zone

我们开发了一种二维电子自旋共振（ESR）成像设备来无损分析断层岩石中的加热事件。二维ESR成像装置除了普通的ESR光谱仪外，还由狭缝腔（狭缝宽度3mmx10mm）、用于100kHz调制场的外部线圈和X-Y平台组成。为了提高二维ESR图像的分辨率，我们对狭缝腔进行了改造，并在狭缝腔上粘贴了一块带有Ф2.6mm针孔的薄黄铜板。因此，分辨率从2~3mm显着提高到0.25mm。我们利用二维ESR成像仪对野岛断层岩进行了一维连续ESR测量和二维ESR成像。一维和二维 ESR 测量的目标 ESR 信号是氧化铁的亚铁磁共振 (FMR) 信号，该信号通过加热产生并增加。结果，我们成功地探测到了古代重复地震中0.25毫米精度的摩擦生热事件。以如此高精度检测摩擦加热事件在世界上尚属首次。此外，我们研究了一种从一维 ESR 连续数据估计摩擦热温度的新方法，并为其开发了一个分析计算机程序。下一步，我们计划对台湾车龙埔断层钻探项目（TCDP）B孔岩心样品进行二维ESR成像，并估算1999年集集地震中的摩擦热温度，因为该钻探项目被推迟，导致我们在科研项目期间无法测量岩心样品的二维ESR图像。另一方面，我们考虑了如何将二维ESR图像转换为二维磁化率图，并通过与标准镍样品（54.56 emu/g）对比，实际制作了磁铁矿、蛇纹岩、辉长岩、野岛断层岩、车笼铺断层岩等天然岩石的二维磁化率图。此外，我们对褐煤和泥岩的氧化铁和镜质体反射率的FMR信号进行了基础研究，将这些指标应用于野岛断层和车笼铺断层钻芯样本的摩擦加热，并分别估算了1995年神户地震和1999年ChiChi地震的摩擦热温度。较少的

We have developed a 2-Dimensional electron spin resonance (ESR) imaging apparatus to nondestructively analyze heating events in fault rocks. The 2-D ESR imaging apparatus is composed of a slit cavity (slit width 3mmx10 mm), an external coil for 100kHz modulation field and an X-Y stage, in addition to an ordinary ESR spectrometer. To improve the resolution of 2-D ESR images, we remodeled the slit cavity and stuck a thin brass plate with a pinhole of Ф 2.6mm on the slit cavity. Consequently, the resolution is considerably improved from 2~3mm to 0.25mm. We have carried out 1-D continuous ESR measurement and 2-D ESR imaging of Nojima fault rocks using the 2-D ESR imaging apparatus. The target ESR signal for the 1-D and 2-D ESR measurements is a ferrimagnetic resonance (FMR) signal of iron oxides, which are generated and increased by heating. As a result, we have succeeded in detecting with precision of 0.25mm frictional heating events during ancient repeated earthquakes. The detection of f … More rictional heating events with such a high precision is the first in the world. Furthermore, we have studied a new method to estimate frictional heat temperature from 1-D ESR continuous data and developed an analytical computer program for it. In the next step, we plan to carry out 2-D ESR imaging of Taiwan Chelungpu Fault Drilling Project (TCDP) Hole B core samples and estimate frictional heat temperature in the 1999 ChiChi Earthquake, because this drilling project was delayed and consequently we could not measure 2-D ESR images of the core samples in the term of our scientific research project. On the other hand, we have considered how to convert a 2-D ESR image into a 2-D magnetic susceptibility map, and actually made 2-D magnetic susceptibility maps of natural rocks such as magnetite ore, serpentinite, gabbro, Nojima fault rocks and Chelungpu fault rocks by comparison with a standard Nickel sample (54.56 emu/g). In addition, we carried out basic studies on FMR signals of iron oxides and vitrinite reflectances of brown coal and mudstone, applied these indicators for frictional heating to Nojima fault and Chelungpu fault drill core samples, and estimated frictional heat temperatures in the 1995 Kobe and 1999 ChiChi Earthquakes, respectively. Less