地震研究

利用云南测震台网波形数据及观测报告,结合构造背景及历史地震活动,从序列活动特征及参数、较大地震的震源机制解及序列精定位等方面分析了2015年3月1日云南沧源M_S5.5地震序列的发震构造及序列分布演化特征。结合震源机制解结果及震区构造,本次地震的发震构造可能为南汀河断裂带(西支)、呈左旋走滑。本次地震的余震活动较弱,序列随时间衰减较快,具有明显的阶段性; 双差重定位结果反映其主体破裂区为北北东向、近似竖直的带状区域,可能为单侧破裂,且后期的余震呈向浅部及外围区域扩散的趋势。

Using waveform data from seismic network of Yunnan province and their corresponding observation report,combined with the tectonic background and historical seismicity,we discussed seismogenic structure and the distribution and temporal evaluation variation of Cangyuan M_S5.5 earthquake sequence in Yunnan on Mar.1,2015 from the activity characteristics and parameters of the sequence,the focal mechanism solutions of larger events as well as the accurate relocation of the sequence etc..Referring to the focal mechanism solutions and the tectonics in epicenter area,we indicated that the seismogenic structure of Cangyuan earthquake is the west branch of Nantinghe Fault which appearred to be a right-lateral strike-slip faulting.It is showed that the seismicity of aftershock sequences remain low,decayed rapidly with time and appeared the obvious phased.The spatial distribution of the sequences which were relocated by the double-difference relocation algorithm showed that the main rupture area was a zonal area of NNEin approximately vertical direction.It seemed to be a unilateral rupture,furthermore,the distribution of the later aftershocks showed the scatter trend to the shallower and outer region of the epicenter.

引言
1 地震活动概况
2 地震序列活动分析
3 较大地震震源机制解分析
4 双差重定位结果分析
5 讨论与结论

图1 2015年3月1日云南沧源MS5.5地震序列震中与云南测震台网的台站分布<br/>Fig.1 Distribution of epicentres of Yunnan Cangyuan MS5.5 earthquake sequence on Mar.1,2015,and the stations of Yunnan seismic network

图1 2015年3月1日云南沧源MS5.5地震序列震中与云南测震台网的台站分布
Fig.1 Distribution of epicentres of Yunnan Cangyuan MS5.5 earthquake sequence on Mar.1,2015,and the stations of Yunnan seismic network

图2 云南沧源MS5.5地震震中附近1°范围历史地震分布<br/>Fig.2 Distribution of historical earthquakes in 1°area of Yunnan Cangyuan MS5.5 earthquake

图2 云南沧源MS5.5地震震中附近1°范围历史地震分布
Fig.2 Distribution of historical earthquakes in 1°area of Yunnan Cangyuan MS5.5 earthquake

表1 沧源地震序列中ML≥3.0地震目录<br/>Tab.1 Catalog of ML≥3.0 earthquakes in Cangyuan earthquake sequence

表1 沧源地震序列中ML≥3.0地震目录
Tab.1 Catalog of ML≥3.0 earthquakes in Cangyuan earthquake sequence

图3 云南沧源MS5.5地震序列M-t图(除MS5.5主震外地震均为ML震级)<br/>Fig.3 M-t diagram of the Yunnan Cangyuan MS5.5 earthquake sequences (the magnitudes of earthquakes are ML except the MS5.5 mainshock)

图3 云南沧源MS5.5地震序列M-t图(除MS5.5主震外地震均为ML震级)
Fig.3 M-t diagram of the Yunnan Cangyuan MS5.5 earthquake sequences (the magnitudes of earthquakes are ML except the MS5.5 mainshock)

图4 云南沧源MS5.5地震序列b值(a)和p值(b)<br/>Fig.4 Cruves of b value(a)and p value(b)of Yunnan Cangyuan MS5.5 earthquake sequence

图4 云南沧源MS5.5地震序列b值(a)和p值(b)
Fig.4 Cruves of b value(a)and p value(b)of Yunnan Cangyuan MS5.5 earthquake sequence

表2 序列中较大地震的震源机制解<br/>Tab.2 Focal mechanism solutions of the events with large magnitude in sequence

表2 序列中较大地震的震源机制解
Tab.2 Focal mechanism solutions of the events with large magnitude in sequence

图5 震源机制解P(a)、T(b)轴方位角玫瑰图<br/>Fig.5 Rose graphs of azimuths of P(a)and T(b)axis in focal mechanisms

图5 震源机制解P(a)、T(b)轴方位角玫瑰图
Fig.5 Rose graphs of azimuths of P(a)and T(b)axis in focal mechanisms

图6 重定位使用的数据:(a)台站及地震序列(左下角框内)分布;(b)Pg、Sg波震相走时<br/>Fig.6 Data used in relocation:(a)the distributions of stations and seismic sequences(the rectangle in left-bottom corner);(b)traveling time curves of Pg and Sg wave

图6 重定位使用的数据:(a)台站及地震序列(左下角框内)分布;(b)Pg、Sg波震相走时
Fig.6 Data used in relocation:(a)the distributions of stations and seismic sequences(the rectangle in left-bottom corner);(b)traveling time curves of Pg and Sg wave

图7 重定位结果及震源机制解在水平面(a)、AA'方向(b)及BB'方向(c)上的投影<br/>Fig.7 The distribution of sequences after relocation and the projection of focal mechanisms on horizontal plane(a),along AA'(b)and BB'(c)directions

图7 重定位结果及震源机制解在水平面(a)、AA'方向(b)及BB'方向(c)上的投影
Fig.7 The distribution of sequences after relocation and the projection of focal mechanisms on horizontal plane(a),along AA'(b)and BB'(c)directions

图8 震源深度随时间的演化<br/>Fig.8 The temporal variations of the focal depth of sequence

图8 震源深度随时间的演化
Fig.8 The temporal variations of the focal depth of sequence

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备注

引言

1 地震活动概况

2 地震序列活动分析

3 较大地震震源机制解分析

4 双差重定位结果分析

5 讨论与结论

期刊信息