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

我们研制了一台二维电子自旋共振(ESR)成像仪，用于非破坏性地分析断层岩中的加热事件。该二维ESR成像装置除普通的ESR光谱仪外，还包括一个狭缝腔(狭缝宽度3 mm×10 mm)、一个用于100 kHz调制场的外线圈和一个X-Y工作台。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个针孔为Ф2.6 mm的薄黄铜板。分辨率由原来的2~3 mm提高到0.25 mm。利用二维ESR成像仪对野岛断裂岩进行了一维连续ESR测量和二维ESR成像。一维和二维ESR测量的目标ESR信号是铁氧化物的铁磁共振(FMR)信号，铁氧化物是通过加热产生和增加的。因此，我们成功地探测到了古代重复地震中0.25毫米的摩擦加热事件。F-…的检测如此高精度的更剧烈的供暖事件在世界上是第一次。此外，我们还研究了一种由一维ESR连续数据估算摩擦热温度的新方法，并编制了相应的分析计算程序。下一步，我们计划对台湾车伦堡断层钻探计划(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，因为这项钻探工程被推迟了，因此我们无法在科研项目期间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，并实际绘制了磁铁矿、蛇纹岩、辉长岩、诺吉马断裂岩和车龙堡断裂岩等天然岩石的二维磁化率图，并与标准镍样品(54.56emu/g)进行了对比。此外，我们对褐煤和泥岩的铁氧化物铁磁共振信号和镜质组反射率进行了基础研究，并将这些摩擦加热指标应用于野岛断裂和车龙铺断裂钻芯样品，分别估算了1995年神户地震和1999年集集地震的摩擦热温度。较少

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