岷县漳县6.6级地震前天水花牛水氡异常可靠性研究

Reliability Study on Water Radon Concentration Anomaly of Huaniu Spring in Tianshui before Minxian-Zhangxian M_s6.6 Earthquake

2013年岷县漳县6.6级地震前甘肃天水花牛的水氡出现了与汶川8.0级地震极为相似的异常变化并在震前已被重点跟踪。为了对花牛水氡2013年出现的异常与岷县漳县地震的关系给出合理的判断,本文分析了花牛水氡正常的趋势背景和年变化形态,给出了正常背景和异常变化的判别指标;分析了花牛水氡的主要影响因素,认为气温是花牛水氡出现年变的主要因素,日降雨量达到一定量级才能引起水氡的短暂变化;着重从水氡泖j值的可靠性、影响因素的不一致性、多学科前兆变化的协调性、异常的重现性、异常与岷县地震的时空相关性等方面对2013年4月以来的异常进行了详细的分析和论证。研究结果可以判定,2013年4月以来天水花牛水氡出现的异常作为岷县漳县6.6级地震的异常是可信并可靠的。

Since April 2013,the water radon concentration of Huaniu Spring has shown abnormal changes that are very similar to the precursory anomaly of the Wenchuan MS8.0 earthquake.From the beginning,it was tracked as important anomaly.Although this change began three months prior to the Minxian-Zhangxian MS6.6 earthquake,we could not conclude that it was a precursor to this earthquake it.Further research is needed to determine a reasonable relationship between the anomaly of water radon concentration and the Minxian-Zhangxian MS6.6 earthquake.In the present study,we analyze the tendency of annual changes in radon concentration of Huaniu Spring,Tianshui,China,which began in April 2013 and terminated after the Minxian-Zhangxian MS6.6 earthquake.The results show a decline tendency with a fixed rate.The annual change is high in summer and low in winter,and the radon concentration is higher than that recorded during the corresponding period of the previous year.In addition,we analyze the main factors that influence the radon concentration,and we determine that the annual change is caused by atmospheric temperature.Abnormal changes in radon concentration occur when the rainfall reaches a particular value; however,the duration is short.Analysis of the reliability of the radon concentration anomaly indicates that although the result is shown to be dependable,it is not consistent with the influencing factors.Moreover,we analyze the relationship of the radon concentration in Huaniu Spring and the earth resistivity and water temperature in Tianshui.The results show that their anomalies began at the same time; however,their change directions differed.The water temperature and earth resistivity showed high anomalies,and the radon concentration anomaly was low.We also analyze the reproducibility of the radon concentration anomaly.The anomaly characteristics of the radon concentration beginning in April 2013 were very similar to the precursory anomaly of the Wenchuan MS8.0 earthquake.Finally,we examine the temporal and spatial relationship between the radon concentration anomaly and the Minxian-Zhangxian earthquake.We conclude that the radon concentration anomaly of Huaniu Spring beginning in April 2013 is a credible and reliable precursory anomaly of the Minxian-Zhangxian MS6.6 earthquake.