地震研究

利用鲁甸MS6.5地震震区及其周边的5个台站所记录的2013年1月至2015年12月三分量地震背景噪声数据,在不同频带内计算自相关格林函数,通过30天滑动叠加获得当前格林函数,对整个研究时段格林函数长时间叠加得到参考格林函数。进一步对当前格林函数和参考格林函数分别采用移动窗互谱、伸缩技术计算各台站相对波速变化,利用计算结果研究鲁甸地震前后波速变化特征。结果表明:移动窗互谱法与伸缩法测量得到的相对波速变化趋势较为一致; 0.2～0.5 Hz频带范围内测量的相对波速变化对介质的敏感深度约为4 km,具有较强的年变趋势,鲁甸地震及永善地震发生后各台站呈现出较显著的同震波速变化,表现为明显的波速下降,其中ZAT台(昭通)、YAJ台(盐津)波速下降最大,达0.06%。整个研究时段波速变化呈现出“扰动-地震-降低-恢复抬升-地震-降低-恢复-扰动”的总体特征。0.5～1 Hz频带测量结果,未观测到明显的同震波速变化,但可见一定的季节性变化特征。

Firstly,using three component seismic background noise data recorded by 5 seismic stations located around the Ludian MS6.5 earthquake area from Jan.2013 to Dec.2015,we calculated autocorrelation Green function in different frequency.Secondly,we obtained the “Current Green function” by the stacking of autocorrelation Green function by sliding window with 30 days as window and 1 day as step and the “Referent Green function” by the stacking of autocorrelation Green function in the whole study time.Finally,based on “current Green function” and “referent Green function”,we calculated the relative wave velocity variation of each station by Moving Window Cross Spectrum(MWCS)and Stretching technology to analyze the relative variation characteristics of wave velocity before and after the Ludian MS6.5 earthquake.The results show that the variation of relative wave velocity by two methods was consistent well.The sensitive depth of the measured relative wave velocity in 0.2～0.5 Hz to the medium is about 4 km,and the wave velocity have a strong annual variation trend.After the Ludian earthquake and the Yongshan earthquake,the coseismic wave velocity variation of stations is significant,which showed as a significant decrease,and the wave velocity of Zhaotong(ZAT)and Yanjin(YAJ)Stations decreased reached 0.06%.The wave velocity variation in the whole study period shows the overall characteristics of “disturbance-earthquake-decrease-recovery and uplift-earthquake-decrease-recovery-disturbance”.We didn't observe obvious wave velocity changes,however,some seasonal variation characteristics are shown in the frequency of 0.5～1 Hz measuring results.

引言
1 数据选取和研究方法
2 计算结果
3 讨论
4 结论

图1 台站分布及鲁甸地震震中位置<br/>Fig.1 Distribution of seismic stations and the epicenter of the Ludian earthquake

图1 台站分布及鲁甸地震震中位置
Fig.1 Distribution of seismic stations and the epicenter of the Ludian earthquake

图2 QIJ台垂直分量(Z)30天滑动平均自相关格林函数(a)及参考格林函数(b)(0.2～0.5 Hz)<br/>Fig.2 Vertical component of 30-day's moving averaged autocorrelation functions(a)and referent green function(b)of the station QIJ(0.2～0.5 Hz)

图2 QIJ台垂直分量(Z)30天滑动平均自相关格林函数(a)及参考格林函数(b)(0.2～0.5 Hz)
Fig.2 Vertical component of 30-day's moving averaged autocorrelation functions(a)and referent green function(b)of the station QIJ(0.2～0.5 Hz)

图3 QIJ台单分量BHZ(a)、BHE(b)、BHN(c)与三分量叠加平均(d)相对波速变化结果(0.2～0.5Hz)<br/>Fig.3 Relative velocity variations with time for BHZ(a),BHE(b),BHN(c)compooent of seismic station QIJ,average results of three components stacking(d)(0.2～0.5Hz)

图3 QIJ台单分量BHZ(a)、BHE(b)、BHN(c)与三分量叠加平均(d)相对波速变化结果(0.2～0.5Hz)
Fig.3 Relative velocity variations with time for BHZ(a),BHE(b),BHN(c)compooent of seismic station QIJ,average results of three components stacking(d)(0.2～0.5Hz)

图4 ZAT台单分量BHZ(a)、BHE(b)、BHN(c)与三分量叠加平均(d)相对波速变化结果(0.2～0.5Hz)<br/>Fig.4 Relative velocity variations with time for BHZ(a),BHE(b),BHN(c)componet of seismic station ZAT,average results of three componets stacking(d)(0.2～0.5Hz)

图4 ZAT台单分量BHZ(a)、BHE(b)、BHN(c)与三分量叠加平均(d)相对波速变化结果(0.2～0.5Hz)
Fig.4 Relative velocity variations with time for BHZ(a),BHE(b),BHN(c)componet of seismic station ZAT,average results of three componets stacking(d)(0.2～0.5Hz)

图5 QIJ(a)、ZAT(b)、YAJ(c)、XUW(d)、DOC(e)台三分量叠加相对波速变化结果(0.2～0.5Hz)<br/>Fig.5 Relative velocity variations with time for QIJ(a),ZAT(b),YAJ(c),XUW(d)and DOC(e)seismic stations(0.2～0.5Hz)

图5 QIJ(a)、ZAT(b)、YAJ(c)、XUW(d)、DOC(e)台三分量叠加相对波速变化结果(0.2～0.5Hz)
Fig.5 Relative velocity variations with time for QIJ(a),ZAT(b),YAJ(c),XUW(d)and DOC(e)seismic stations(0.2～0.5Hz)

图6 QIJ(a-1、b-1)、ZAT(a-2、b-2)、YAJ(a-3、b-3)、XUW(a-4、b-4)、DOC(a-5、b-5)台相对波速变化年变(a)及去除年变后波速变化(b)(0.2～0.5Hz)<br/>Fig.6 Annual variation of relative velocity(a)and velocity variations after removing annual variation(b) for different seismic stations of QIJ(a-1,b-1),ZAT(a-2,b-2),YAJ(a-3,b-3),XUW(a-4,b-4),DOC(a-5,b-5); 0.2～0.5Hz)

图6 QIJ(a-1、b-1)、ZAT(a-2、b-2)、YAJ(a-3、b-3)、XUW(a-4、b-4)、DOC(a-5、b-5)台相对波速变化年变(a)及去除年变后波速变化(b)(0.2～0.5Hz)
Fig.6 Annual variation of relative velocity(a)and velocity variations after removing annual variation(b) for different seismic stations of QIJ(a-1,b-1),ZAT(a-2,b-2),YAJ(a-3,b-3),XUW(a-4,b-4),DOC(a-5,b-5); 0.2～0.5Hz)

图7 区内QIJ(a)、YAJ(b)、DOC(c)台三分量叠加平均相对波速变化(0.5～1Hz)<br/>Fig.7 Relative velocity variations with time of average value of three components stacking for QIJ(a),YAJ(b)and DOC(c)stations(0.5～1Hz)

图7 区内QIJ(a)、YAJ(b)、DOC(c)台三分量叠加平均相对波速变化(0.5～1Hz)
Fig.7 Relative velocity variations with time of average value of three components stacking for QIJ(a),YAJ(b)and DOC(c)stations(0.5～1Hz)

图8 研究区内各台站QIJ(a-1、b-1)、ZAT(a-2、b-2)、YAJ(a-3、b-3)、XUW(a-4、b-4)、DOC(a-5、b-5)相对波速变化年变(a)及去除年变后波速变化(0.1～0.2Hz)(b)<br/>Fig.8 Annual variation of relative velocity(a)and velocity variations after removing annual variation(0.1～0.2Hz)(b)for different seismic stations of QIJ(a-1,b-1),ZAT(a-2,b-2),YAJ(a-3,b-3),XUW(a-4,b-4),DOC(a-5,b-5)

图8 研究区内各台站QIJ(a-1、b-1)、ZAT(a-2、b-2)、YAJ(a-3、b-3)、XUW(a-4、b-4)、DOC(a-5、b-5)相对波速变化年变(a)及去除年变后波速变化(0.1～0.2Hz)(b)
Fig.8 Annual variation of relative velocity(a)and velocity variations after removing annual variation(0.1～0.2Hz)(b)for different seismic stations of QIJ(a-1,b-1),ZAT(a-2,b-2),YAJ(a-3,b-3),XUW(a-4,b-4),DOC(a-5,b-5)

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备注

引言

1 数据选取和研究方法

2 计算结果

3 讨论

4 结论

期刊信息