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利用介休台微震仪记录资料,对太原、临汾地区1980—1983年间的小地震(M_L=2.0—3.0)进行了波谱分析,引入修改后的平均断错概念:F′=M_L-logs。其结果:平均断错F′值在1.7—3.0之间。采用公式logM_0=1.7M_L+15.1测定地震矩M_0,其量级在0.3—15.8×10~(19)达因·厘米。并用Δσ=CM_0/s~3/2测定应力降,Δσ在0.004—0.65巴范围,等效位错半经r为400—940米之问,拐角频率f_0在2.3一5.6周范用内,海城大地震后,我们对海城地区M_L=2.5—3.9级的70个小地震进行了波谱分析,测定了震源参数。其结果:大震前F′=2.5—3.9之间,Δσ=0.1—16.6巴范围。大震后F′=2.1一2.8之间,Δσ=0.01—0.5巴范围。太原及临汾地区小地震的平均断错F′和应力降Δσ均低于海城大震前小地震的相应数值。对太原、临汾地区小震群地震进行波谱分析的结果表明:在1983年以前,即1980一1982年期间,平均断错F′值和应力降Δσ略高于1983年间。从1983年开始两地区应力背景有下降的趋势。总述以上结果,太原、临汾地区目前应力背景并不高,在近期看不出有孕育大地震应力背景。
By using the data from the trough-table, the spectral analysis of small earthquakes (M_L = 2.0-3.0) from 1980 to 1983 in Taiyuan and Linfen was carried out. The modified mean-break concept was introduced: F ’= M_L-logs. The result: the average fault F ’value between 1.7-3.0. The seismic moment M_0 is measured by the formula logM_0 = 1.7M_L + 15.1, and its magnitude is 0.3-15.8 × 10 ~ (19) dyne centimeters. And Δσ = CM_0 / s ~ 3/2 measured stress drop, Δσ in the range of 0.004-0.65 bar, the equivalent dislocation half r by 400-940 meters Q, the corner frequency f_0 in 2.3 to 5.6 weeks with the Fan within the sea After the Great Earthquake, we performed spectral analysis of 70 small earthquakes of M_L = 2.5-3.9 in Haicheng area and determined the source parameters. The result: F ’= 2.5-3.9 before the earthquake, Δσ = 0.1-16.6 bar range. After a large earthquake F ’= 2.1 a 2.8, Δσ = 0.01-0.5 bar range. The average fault F ’and stress drop Δσ of small earthquakes in Taiyuan and Linfen are lower than the corresponding values of small earthquakes before Haicheng earthquake. The results of spectral analysis of the small earthquakes in Taiyuan and Linfen show that the mean fault F ’and stress drop Δσ were slightly higher than that of 1983 until 1983, that is, from 1980 to 1982. Since 1983, the stress backgrounds in both regions have been declining. Summarizing the above results, the stress backgrounds in Taiyuan and Linfen are not high at present, and it is not clear in the near future that there is a stress background that gives birth to a large earthquake.