Development of Exploration System for Three-Dimensional Temperature Distribution Using Resistivity

我们研究了一种通过浅层和深层的电阻率分布来估计地热场三维温度分布的勘探系统。用电法和大地电磁(MT)法获得了电阻率数据。Mt.Mt.位于九州中部的阿索是一座典型的活火山，被选为研究地点。主要研究结果如下：(1)结合氡运动数值模拟和氡原子数的计算方法，可以从氡浓度的空间分布中估算出断层的宽度、倾角和倾角。断层上具有热液输导作用的断层上的氡浓度由于火山地震的活动而显示出较大的时间变化。(2)我们建立了结合卫星图像提取的线性构造d…来估计和解释裂缝方向的方法。更多重要的高程模型数据和数字地质图。这些方法可用于推断影响热液流动路径的裂隙分布模式。(3)将神经网络和地质统计学相结合的新方法应用于地热调查测井地下温度分布的估计。尽管样本数据量有限，但内插结果揭示了热液流体的高温带和对流模式。(4)电法勘探表明，在近期活动的断层上，近地表的电阻率有下降的趋势。大地电磁法测得的断层深部电阻率分布不均匀，大裂隙带的电阻率特别低。由于TE模和TM模之间的电阻率分布有很大的不同，因此Mt。通过对MT法测得的电阻率与有限元估算的温度的检验，发现了温度越高的部分电阻率越高的一般关系。此外，热液流体放电区下的电阻率比相同温度下的其他区域要低。较少

We examined an exploration system for estimating a three-dimensional temperature distribution in geothermal field through resistivity distribution in the shallow and deep depths. The resistivity data were obtained by electrical exploration and Magneto-Telluric (MT) method. Mt. Aso, which is a typical active volcano and situated in central Kyushu, was chosen as the study site. The main results are summarized as follows.(1) Fault shape concerning width, dip direction, and dip angle can be estimated from spatial distribution of radon concentrations through combination of a numerical simulation for the movement of radon and the calculation method of number of radon atoms. The radon concentrations on a fault, which has a role of conduit for hydrothermal fluids, show large temporal changes attributable to the activity of volcanic earthquakes.(2) We have constructed the estimation and interpretation methods of fracture orientation through a combination of satellite-image derived lineaments, d … More igital elevation model data, and digital geologic map. These methods can be used to infer distribution pattern of fractures that have effect on flow path of hydrothermal fluids.(3) A new method using neural network and geostatistics was applied to estimate distribution of subsurface temperatures from geothermal investigation loggings. In spite of the restricted quantity of sample data, the interpolation results revealed high temperature zones and convection patterns of hydrothermal fluids.(4) Electrical exploration clarified that the resistivity near the ground surface tends to decrease upon a fault which moved recently. The resistivity distribution in the deep depths of a fault, which is obtained by MT method, is not homogeneous, and the resistivity in largely fractured zones is specially low. Because the resistivity distributions between TE mode and TM mode are quite different, the resistivity of Mt. Aso is thought to have strong anisotropic behavior.(5) A general relation that the portion with higher temperature has higher resistivity was found through the examination of the resistivity obtained by MT method and the temperature estimated by a finite element method. Furthermore, the resistivity under the discharge zone of hydrothermal fluids was found to be lower than the other areas with the same temperature. Less