四川芦山MS7.0和汶川MS8.0地震前地电场变化研究

应用四川芦山M_S7.0和汶川M_S8.0震中周围部分地电场观测台站的资料,主要利用地电场波形比较和极化方位变化两种方法,并结合观测台站的工作日志,对两次地震前地电场观测资料进行了分析研究,并得出:芦山M_S7.0和汶川M_S8.0地震前部分台站地电场波形出现变异现象,主要表现为两种形式:日变波形的畸变(如盐源台和泸沽湖台)和相应时段地电场频谱特性出现变化,这些变异基本上出现在震前1~2个月内;利用两次地震前地电场观测的日均值计算了部分观测台站的地电场极化方位,发现在震前地电场的极化方位出现了大幅变化,最大变化幅度达160°,最小变化幅度也有10°;初步研究还发现,两次地震前夕,震中周围部分台站极化方位的正向或反向延长线,相汇集的区域与地震的震中有一定联系;对于研究所得结果,从地震电信号的产生机制和震源特性方面进行了尝试性理论解释.

Study on the geo-electric field variation of Sichuan Lushan MS7.0 and Wenchuan MS8.0 earthquake

Applying the data of geo-electric field observation stations surrounding the epicenter of Sichuan Lushan M_S7.0 and Wenchuan M_S8.0 earthquake, mainly using electric field waveform comparison and polarization orientation changes of two kinds of methods, and combining the observation log of station, we study and analyze the data of the geo-electric field stations before the two earthquakes and conclude that, the anomalous waveform variation before the Lushan M_S7.0 and Wenchuan M_S8.0 earthquake showed mainly two forms: diurnal waveform distortion (such as Yanyuan station and Luguhu station) and the change of geo-electric field frequency spectrum characteristics in the corresponding time, and these variations basically appeared in 1~2 months before the earthquake. Using the daily mean value of geo-electric field observed by part of stations around the epicenter of two earthquakes, we calculated the polarization of geo-electric field before two earthquakes, and found a sharp change in the polarization direction before the earthquake, the largest change was 160°, and minimum change 10°. A preliminary study also found that, before the two earthquakes, the intersection region and the epicenter seems to have some sort of connection, the intersection region formed by polarization orientation forward or reverse extension line; for the results obtained in this study, a tentative theoretical explanation from the generation mechanism of seismic electric signals and the focal mechanism of the two earthquakes.