摘要
利用中法合作的天祝电测台从 1 994年 1 0月至 1 997年 6月每分钟的观测资料 ,使用常规分析方法、分数维方法、垂直极化方向投影法和MT定点测深二维反演方法处理后 ,发现在 1 995年 7月 2 2日永登 5.8级地震 (Δ=84km)和 1 996年 6月 1日天祝 5.4级地震 (Δ =65km)前 ,4种方法、5种参数不同程度地显现出短临异常 ,并表现出较好的协调性 .其中分数维异常和主轴视电阻率异常显示了明显的方向性 .地电场异常对与台站同处一条断裂带上天祝地震的孕震过程反映更敏感 .还从 4个方面讨论了异常的可靠性 ,并提出了产生异常的可能机理 .认为永登 5.8级地震前大地电场异常由主要是震源处的电磁辐射以及台站下方 7km左右介质电性变化共同产生 ;而天祝地震前异常主要由台站下方 5～ 3 0km范围内沿断裂走向的岩石电阻率变化所致 .
After processing the data of geoelectric field and geomagnetic component from Tianzhu sino France coorperate station in Oct.1994 to Jun.1997,with methods of mean value analysis,fractional dimension,vertical polarization direction projection and two dimension inversion of fixed set MT, it is found out that the 5 parameters in the 4 methods take on short impending anormalies in different extent before Yongdeng M S 5.8 earthquake (Δ=84 km) on July 22,1995 and Tianzhu M S 5.4 earthquake (Δ=65 km) on June 1,1996.All these anormalies show good coordination,and the fractional dimension and principal axis apparent resistivity anormalies show clear orientation.The anormalies of geoelectric field is more sensitive to the earthquake preparation process of Tianzhou event which took place on the same fault with the station.The anormaly reliability is discussed from 4 points and the anormaly possible mechanism is given. It is suggested that the geoelectric anormaly before Yongdeng M S5.8 earthquake is produced mainly by the focus electromagnetic radiation,comline with electric property variation of medium under the station at depth of 7 km,while before Tianzhu M S5.4 earthquake mainly by the resistivity variation of rock along the fault strike at depth of 5～30 km under the station .
出处
《西北地震学报》
CSCD
北大核心
2002年第1期56-64,共9页
Northwestern Seismological Journal
基金
中国地震局兰州地震研究所论著编号 :LC2 0 0 2 0 13
