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Construction of Evaluation System for Earthquake Response of Active Fault by Continuous Measurement of Radon Gas

氡气连续测量活断层地震反应评价体系构建

基本信息

批准号：
09555322
负责人：
KOIKE Katsuaki
金额：
$ 4.16万
依托单位：
Kumamoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09555322/
关键词：
Radon Ionization chamber method Fracture system Active fault Fumarole area Periode Volcanic seismicity Earth tide シンチレーションカウンター法液体シンチレーションカウンター法

项目摘要

In order to measure the radon concentration in soil gas continuously and stably, we have adopted the ionization chamber method and used the equipment, Alpha GUARD (Genitron Inc.), for the measurement By this equipment, the several kinds of data such as ^<222>Rn concentration (Bq/m^3), temperature, atmospheric pressure, humidity, and data quality can be obtained at time interval of 10 minutes. A hot spring area with the active fumaroles, situated in the western side of Mt. Aso and on the NNW-SSE trending fault, was chosen as the study site. The soil gas was inhaled at the rate of 0.5 l/mm from the 1-m depth observation hole. We paid special attention to rem'oving water drops from the inhaled gas and maintaining the temperature and the humidity around the Alpha GUARD almost constant.By analyzing the 24,419 measurement data which have been taken from August 11, 1998, it was clarified that the correlation between the radon concentration and the weather factors such as the temperature, the atmospheric pressure, and the humidity were generally low and the radon concentration changed largely within the range of 0.4*10^5 Bq/m^3 in a day. But the average of radon concentrations in a day shows the temporal change that can be approximated by a smooth curve. This can be considered as trend component.As the result of spectral analysis using the maximum entropy method, the changes of radon concentrations were revealed to contain predominant period of 24 hours and weak period of 12 hours. These periods correspond with those of two major elements in the earth tide. Furthermore, the radon concentrations were found to increase largely on the periods of high volcanic seismicity. It can be concluded that the disturbance of subsurface temperature and pressure resulted from the earthquakes affects the trend of radon concentrations and the earth tide induces the concentration changes with short periods superimposed on the trend.

为了连续、稳定地测量土壤气中的氡浓度，我们采用了电离室法，使用了Alpha GUARD（Genitron Inc.）该装置<222>可在10分钟内获得氡浓度（Bq/m^3）、温度、气压、湿度等多种数据，并可获得数据质量。温泉区，有活跃的火山口，位于山的西侧。研究地点选在阿索和北北西-南东向断层上。从1米深的观察孔以0.5升/毫米的速率吸入土壤气体。通过对1998年8月11日以来的24,419个测量数据的分析，阐明了氡浓度与气温、气压、空气湿度等气象因素的关系，并对氡浓度与大气环境的关系进行了探讨。空气湿度普遍较低，氡浓度日变化较大，在0.4 × 10^5Bq/m^3范围内。但氡浓度的日平均值显示了时间变化，可以用平滑曲线近似。最大熵谱分析结果表明，氡浓度的变化有24 h的优势周期和12 h的弱周期。这些周期与固体潮中两个主要元素的周期相对应。此外，氡浓度增加很大程度上对高火山地震活动的时期。结果表明，地震引起的地下温度和压力的扰动影响了氡浓度的变化趋势，固体潮引起的氡浓度变化具有叠加在趋势上的短周期特征。