地震研究

对2011年3月10日云南盈江5.8级地震序列作跟踪分析,提出了适合该地震序列趋势判断的部分方法。在该序列M≥4.8地震的几个子序列中,前震h值均小于1,较准确地判定了地震趋势; 在前震和余震序列中b值没有出现前震序列低余震序列高的现象,因而用b值对该序列的判断是失败的; 大盈江断裂上距离不远在类型相同的地震第1天的衰减方式有相似之处,可以为快速判定地震类型提供依据; 本次5.8级地震是大盈江断裂在北北东向的主压应力作用下产生左旋走滑错动的结果,该序列3.6级以上地震的震源机制解显示主震发生后小震P、T轴出现了快速变化,从而为地震类型的判定提供了参考依据; 主震发生后余震震中分布出现了北西向的共轭条带分布,这可能意示着主震发生后在原震源区发生更大地震的可能性较小。

We tried the h-value and b-value to trace the M_S5.8 Yingjiang earthquake sequence and found that:(1)h-value after the Yingjiang M_S4.8 earthquake on January 2 was 0.6,and the one after the M_S4.8 earthquake on February 1 was 0.8. Both were less than 1. So we concluded that the two earthquakes were foreshocks and there would be a larger earthquake. The M_S5.8 earthquake occurring on Mar.10 proved our judgment right.(2)b-value after the M_S4.8 Yingjiang earthquake on January 2 was 0.77,and the one after the M_S4.8 earthquake on February 1 was 0.82,according to these two high b-values we concluded that there would be no larger earthquakes anymore and we failed. Comparing the M_S5.1 Yingjiang earthquake sequence on Mar.21,2008 with the M_S5.8 earthquake sequence on Mar.10,we found that the earthquakes occurred closely on the Dayingjiang Fault showed the same characters of energy attenuation in the first day of the main shock. This regularity is helpful for the fast determination of the earthquake pattern. The M_S5.8 earthquake resulted from the left-lateral,strike-slip faulting of the Dayingjiang Fault. Calculating the focal mechanisms of thirteen M≥3.6 events of the sequence,we found that P-axis and T-axis greatly changed. This regularity is also helpful for pattern determination. The epicenters of the aftershocks distributed conjugately in North-West direction,which means that the probability of another larger earthquake in the source region was small.

引言
1 盈江地震序列基本情况和衰减特征分析
2 震源机制和地震精定位
4 认识和讨论

表1 2011年3月10日盈江5.8级地震序列M≥4.5地震参数<br/>Tab.1 Catalog of M≥4.5 events in Yingjiang MS5.8 sequence of Mar.10,2011

表1 2011年3月10日盈江5.8级地震序列M≥4.5地震参数
Tab.1 Catalog of M≥4.5 events in Yingjiang MS5.8 sequence of Mar.10,2011

图1 盈江5.8级地震序列ML≥2地震M-t图(a)和ML≥3地震时间间隔曲线图(b)<br/>Fig.1 Diagram of M-t(ML≥2 earthquakes)(a)and dt-t(ML≥3 earthquakes)(b)in Yingjiang MS5.8 sequence

图1 盈江5.8级地震序列ML≥2地震M-t图(a)和ML≥3地震时间间隔曲线图(b)
Fig.1 Diagram of M-t(ML≥2 earthquakes)(a)and dt-t(ML≥3 earthquakes)(b)in Yingjiang MS5.8 sequence

图2 盈江ML≥1地震震中分布图(空心圆圈表示2008年3月21日盈江5.1级地震序列; 实心圆圈表示2011年3月10日盈江5.8级地震序列)<br/>Fig.2 Epicenter distribution with ML≥1 of the Yingjiang MS5.8 sequence (hollow circles stand for MS5.1 sequence on Mar. 21,2011,solid circles stand for MS5.8 sequence on Mar. 10,2011)

图2 盈江ML≥1地震震中分布图(空心圆圈表示2008年3月21日盈江5.1级地震序列; 实心圆圈表示2011年3月10日盈江5.8级地震序列)
Fig.2 Epicenter distribution with ML≥1 of the Yingjiang MS5.8 sequence (hollow circles stand for MS5.1 sequence on Mar. 21,2011,solid circles stand for MS5.8 sequence on Mar. 10,2011)

图3 盈江地震序列M-t图(a)2008-03-21盈江5.1级地震;(b)2011-01-01～2011-01-02盈江4.6、4.8级地震;(c)2011-02-01盈江4.8级地震;(d)2011-03-10盈江5.8级地震<br/>Fig.3 Diagram of M-t of Yingjiang sequence (a)MS5.1 sequence on Mar. 21,2008;(b)M4.6,4.8 sequence on Jan. 1-2,2011;(b)M4.8 sequence on Feb. 1,2011;(d)MS5.8 sequence on Mar. 10,2011

图3 盈江地震序列M-t图(a)2008-03-21盈江5.1级地震;(b)2011-01-01～2011-01-02盈江4.6、4.8级地震;(c)2011-02-01盈江4.8级地震;(d)2011-03-10盈江5.8级地震
Fig.3 Diagram of M-t of Yingjiang sequence (a)MS5.1 sequence on Mar. 21,2008;(b)M4.6,4.8 sequence on Jan. 1-2,2011;(b)M4.8 sequence on Feb. 1,2011;(d)MS5.8 sequence on Mar. 10,2011

表2 2011年盈江5.8级地震震源机制解对比表<br/>Tab.2 Acomparison among different institude or author

表2 2011年盈江5.8级地震震源机制解对比表
Tab.2 Acomparison among different institude or author

图4 盈江序列M≥3.6 地震震源机制解示意图<br/>Fig.4 Focal mechanism solutions of M≥3.6 events of Yingjiang sequence

图4 盈江序列M≥3.6 地震震源机制解示意图
Fig.4 Focal mechanism solutions of M≥3.6 events of Yingjiang sequence

图5 P轴和T轴时间进程曲线<br/>Fig.5 Curve of P-axis and T-axis

图5 P轴和T轴时间进程曲线
Fig.5 Curve of P-axis and T-axis

表3 盈江地区水平层状地壳速度模型<br/>Tab.3 Horizontal layered crustal velocity model in Yingjiang area

表3 盈江地区水平层状地壳速度模型
Tab.3 Horizontal layered crustal velocity model in Yingjiang area

图6 盈江地震序列精确定位结果示意图<br/>Fig.6 Epicenter distribution after accurate relocation

图6 盈江地震序列精确定位结果示意图
Fig.6 Epicenter distribution after accurate relocation

图7 2011年1月1日～3月9日盈江地震序列震中分布图<br/>Fig.7 Epicenter distribution of earthquakes from Jan.1 to Mar.9,2011 after accurate relocation

图7 2011年1月1日～3月9日盈江地震序列震中分布图
Fig.7 Epicenter distribution of earthquakes from Jan.1 to Mar.9,2011 after accurate relocation

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备注

引言

1 盈江地震序列基本情况和衰减特征分析

2 震源机制和地震精定位

4 认识和讨论

期刊信息