祁连山—河西走廊地区5级以上地震前水氡短临异常特征

在充分整理单台水氡资料的基础上,对发生在祁连山—河西走廊活动断裂系的5级以上地震进行了短临阶段水氡异常的分析研究。内容主要包括:异常出现的频次、持续时间、异常结束到发震的时间、异常的范围等。进而对该地区5级以上地震水氡短临前兆异常的特征作了归纳。

Short-impending Period Anomalous Characteristics of Radon in Ground Water before Earthquakes with M≥5.0 in the Area between Qilian Mountain and the Hexi Corridor

On the basis of analysis of the radon data recorded by single station, the short-impending period anomalies of earthquakes with M≥5. 0 in the area between Qilian Mountain and the Hexi Corridor are statistically analyzed in the paper. These include anomaly frequency, duration, the interval from the ceassion of anomalies to earthquake occurrence, the anomalous area, especially the short-impending earthquake prediction items of precursory anomalies in the studied area. By analyzing 8 typical earthquakes, it is shown that the short-impending characteristics of precursory anomalies of radon in ground water before strong earthquakes in the studied area are as follows: (1)The main shape of the short-impending precursory anomaly of radon is jump-descending variation, and the precursory amplitude values are large. (2)The earliest time of the short-impending anomaly beginning is 3 moths and 20 days, especially 2-40 days before the earthquake. The anomaly process is undulatory, synchronizing and group or coupled. (3)The characters of short-impending precursory field are changed with the earthquake epicenters in the studied area. The main anomaly is near field in 400 km in middle-east segment of Qilian Mountain, which shows that the anomalies are migrated from outer to the focus in 40-390 km; but in west segment of Qilian Mountain, the main anomaly is far field beyond 400 km and the migration is not obvious. And this help to predict the earthquake epicenter.(4)The earthquakes occurred after 15- 80 days when the short-impending anomalies stopped. Some occurred when the anomalies were at turning points or just before stopping, the fewer occurred when the anomalies were changing.