嘉峪关气氡浓度异常与2021年玛多MS7.4地震关系分析

嘉峪关气氡浓度在多年上升的背景下,于2017年出现了转折异常变化,但祁连山地震带内一直没有发生与异常幅度和持续时间相匹配的地震,直到2021年5月22日,在距离嘉峪关气氡测点570 km的玛多发生M_S7.4地震。为了判断嘉峪关气氡浓度异常与玛多地震的关系,结合震例,从异常信度、震前异常特征、震后异常变化及地质构造背景等方面对其进行深入分析。结果发现:嘉峪关气氡浓度的异常特征与地震所处的构造有关,发生在祁连山地震带内的地震,气氡浓度异常表现为1年或半年尺度的年畸变,发生在该地震带以外远距离的地震,气氡浓度异常表现为多年的趋势性变化;玛多地震发生后,嘉峪关气氡浓度下降速率减缓之后转折,呈恢复状态;嘉峪关气氡测点与玛多地震都位于青藏高原东北部,具有相同的动力背景且在构造上具有关联性。综合分析认为嘉峪关气氡多年趋势异常与玛多M_S7.4地震有关,研究对建立可靠的异常指标体系、提高地震预测水平具有重要意义。

Relationship between abnormal gas radon concentration inJiayuguan and Maduo MS7.4 earthquake of 2021

Under the background of rising gas radon concentration in Jiayuguan for many years, an unprecedented change occurred in 2017. However, no earthquake matching the amplitude and duration of the anomaly has occurred in the Qilian Mountains seismic belt. On May 22, 2021, an M_S7.4 earthquake occurred in Maduo, which is 570 km away from the radon measuring point in Jiayuguan. An in-depth analysis of the anomaly reliability, anomaly characteristics before the earthquake, anomaly change after the earthquake, and geological structure background was conducted in this study to determine the relationship between the radon concentration anomaly of gas in the Jiayuguan and Maduo earthquakes. Results show that the anomalous characteristics of the gas radon concentration in Jiayuguan are related to the structure where the earthquake occurred. The anomaly of gas radon concentration shows an annual distortion of 1 year or 6 months for earthquakes that occur along the Qilian Mountains seismic zone. By contrast, the anomaly demonstrates a long-term change in the propensity for earthquakes that occur far away from the Qilian Mountains seismic zone. The decreasing rate of radon concentration in Jiayuguan slowed down and then turned to a recovery state after the Maduo earthquake. The measuring points for gas radon concentration in the Jiayuguan and Maduo earthquakes are both located in the northeastern part of the Tibetan Plateau with the same dynamic background and structural correlation. The comprehensive analysis shows that the tendency anomaly of gas radon in Jiayuguan may be related to the Maduo M_S7.4 earthquake. This study is of considerable importance in establishing a reliable anomaly index system and improving earthquake prediction.