汶川地震前电离层VTEC的异常响应

Anomalous response of ionospheric VTEC before the Wenchuan earthquake

2008年5月12日我国四川省汶川县发生了8.0级大地震,基于中国地壳运动观测网络(CMONOC)的GPS观测数据,解算得到了震中上空附近的电离层VTEC;以VTEC的滑动均值为背景参考值,以2倍均方差作为误差限值,对临震一个月的VTEC资料进行了处理分析.结果显示,在震前多次出现VTEC的异常扰动,其中4月29日、5月6—7日为异常减少,5月9日为异常增加,而且电离层VTEC的异常驼峰有向磁赤道漂移的趋势.由于距离发震时刻较近,排除其它因素后可能源于此次地震引起的电离层效应.

An earthquake of Ms8.0 struck Wenchuan county of Sichuan province on 12 May 2008. In this paper, on the basis of the GPS observation data obtained from the reference stations of Crustal Movement Observational Network of China, the continuous 30-day VTEC （vertical total electron content） value over the epicenter is computed and then the abnormal signals are identified with 2-multiple standard deviation of 10-day VTEC value as limit range. The result shows that there are the ionospheric anomalies prior to the earthquake onset：the apparent anomalous reduction of VTEC occurred on 29 April and during 6th-7th of May, while the VTEC value abnormally increased on 9 May. It has also been shown that the anomalous crest of the VTEC moved towards equator. Due to the time is close to the moment of the Wenchuan earthquake occurrence, we may conclude that the ionospheric anomalies do exist and are possibly related to the earthquake, excluding other possible factors.