2014年鲁甸M_S6.5地震前后介质波速变化特征分析
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摘要
本文利用研究区内13个地震台站2014年1月至12月的连续波形数据,采用背景噪声互相关方法,提取了2014年8月3日鲁甸M_S6.5地震的同震波速变化。结果表明,鲁甸地震对介质波速的影响具有明显的空间差异性,较大幅度的同震波速变化主要集中于则木河断裂—小江断裂及莲峰断裂区域。其中,莲峰断裂SW段和则木河断裂NW段区域的波速出现了较为明显的同震降低,则木河断裂和小江断裂交界处则出现了明显的波速升高。通过对比研究区内介质波速的同震变化与鲁甸地震对周边主要活动断裂应力积累的影响后发现,波速变化与应力变化在空间分布上具有较高的一致性,且两者的变化幅度也成正相关关系。由此可以看出,鲁甸地震造成的应力变化可能是地下介质波速变化的主要原因。采用相同的方法对2014年4月5日永善MS5.1地震研究后发现,永善地震后鲁甸地震震源区及其附近区域波速明显升高。
In this paper,we extracted seismic velocity changes associated with the 2014 Ludian M_S6. 5 earthquake from ambient noise cross-correlation by using continuous seismic data recorded by 13 seismic stations in the research area. Base on temporal changes of seismic velocity of each seismic station pair,we got the spatial distribution of seismic velocity changes,and found that it has significant regional variation. The great changes are mainly distributed on the zones of Zemuhe fault,Xiaojiang fault and Lianfeng fault. There is a sudden post-seismic velocity drop for the region of the southwest segment of the Lianfeng fault and the northwest segment of the Zemuhe fault,and there is a sudden post-seismic velocity increase for the junctional zone of Zemuhe fault and Xiaojiang fault. We found that post-seismic velocity change and stress change have high consistency in the spatial distribution by comparing the stress accumulation of the main active faults around the Ludian earthquake. And there was a positive correlation between co-seismic velocity change and co-seismic stress change. Therefore,stress change associated with the Ludian earthquake may be the main reason of seismic velocity change. We extracted the co-seismic velocity changes associated with the M_S5. 1 Yongshan earthquake of April 5,2014 by the same method.The result showed that seismic velocity increased in the source area of the Ludian earthquake after the Yongshan earthquake.
In this paper,we extracted seismic velocity changes associated with the 2014 Ludian M_S6. 5 earthquake from ambient noise cross-correlation by using continuous seismic data recorded by 13 seismic stations in the research area. Base on temporal changes of seismic velocity of each seismic station pair,we got the spatial distribution of seismic velocity changes,and found that it has significant regional variation. The great changes are mainly distributed on the zones of Zemuhe fault,Xiaojiang fault and Lianfeng fault. There is a sudden post-seismic velocity drop for the region of the southwest segment of the Lianfeng fault and the northwest segment of the Zemuhe fault,and there is a sudden post-seismic velocity increase for the junctional zone of Zemuhe fault and Xiaojiang fault. We found that post-seismic velocity change and stress change have high consistency in the spatial distribution by comparing the stress accumulation of the main active faults around the Ludian earthquake. And there was a positive correlation between co-seismic velocity change and co-seismic stress change. Therefore,stress change associated with the Ludian earthquake may be the main reason of seismic velocity change. We extracted the co-seismic velocity changes associated with the M_S5. 1 Yongshan earthquake of April 5,2014 by the same method.The result showed that seismic velocity increased in the source area of the Ludian earthquake after the Yongshan earthquake.
引文
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[10]Stehly L,Froment B,Campillo M,et al.Monitoring seismic wave velocity changes associated with the MW7.9 Wenchuan earthquake:Increasing the temporal resolution using curvelet filters[J].Geophysical Journal International,2015,201:1 939-1 949.
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[13]Derode A,Larose E,Tanter M,et al.Recovering the Green’s function from field-field correlation in an open scattering medium[J].Acoustical Society of America,2003,113:2 973-2 976.
[14]Campillo M,Paul A.Long-range correlations in the diffuse seismic coda[J].Science,2003,299(5606):547-549.
[15]Shapiro N M,Campillo M.Emergence of broadband Rayleigh waves from correlations of the ambient seismic noise[J].Geophysical Research Letters,2004,31:L07614.
[16]Brenguier F,Campillo M,Hadziioannou C,et al.Postseismic relaxation along the San Andreas fault at Parkfield from continuous seismological observations[J].Science,2009,321:1 478-1 481.
[17]Sens-Schnfelder C,Wegler U.Passive image interferometry and seasonal variations of seismic velocities at Merapi Volcano,Indonesia[J].Geophysical Research Letters,2006,33:L21302.
[18]Wegler U,Sens-Schnfelder C.Fault zone monitoring with passive image interferometry[J].Geophysical Journal International,2007,168:1 029-1 033.
[19]Brenguier F,Shapiro N M,Campillo M,et al.2008.Towards forecasting volcanic eruptions using seismic noise[J].Nature Geoscience,1:126-130.
[20]刘志坤,黄金莉.利用背景噪声互相关研究汶川地震震源区地震波速度变化[J].地球物理学报,2010,53(04):853-863.
[21]Chen J H,Froment B,Liu Q Y,et al.Distribution of seismic wave speed changes associated with the 12May 2008 MW7.9 Wenchuan earthquake[J].Geophysical Research Letters,2010,37:L18302.
[22]Brenguier F,Clarke D,Aoki Y,et al.Monitoring volcanoes using seismic noise correlations[J].Comptes Rendus Geoscience,2011,343:633-638.
[23]Froment B,Campillo M,Chen J H,et al.Deformation at depth associated with the May 12,2008 MW7.9 Wenchuan earthquake from seismic ambient noise monitoring[J].Geophysical Research Letters,2013,40:78-82.
[24]Brenguier F,Campillo M,Takeda T,et al.Mapping pressurized volcanic fluids from induced crustal seismic velocity drops[J].Science,2014,345:80-82.
[25]Sawazaki K,Kimura H,Shiomi K,et al.Depth-dependence of seismic velocity change associated with the2011 Tohoku earthquake,Japan,revealed from repeating earthquake analysis and finite-difference wave propagation simulation[J].Geophysical Journal International,2015,201:741-763.
[26]Lecocq T,Caudron C,Brenguier F.2014.MSNoise,a python package for monitoring seismic velocity changes using ambient seismic noise[J].Geophysical Research Letters,85(3):715-726.
[27]Bensen G D,Ritzwoller M H,Barmin M P,et al.Processing seismic ambient noise data to obtain reliable broad-band surface wave dispersion measurements[J].Geophysical Journal International,2007,169:1 239-1 260.
[28]Stehly L,Campillo M,Shapiro N M.A study of the seismic noise from its long-range correlation properties[J].Journal of Geophysical Research,2006,111:B10303.
[29]Froment B,Campillo M,Roux P,et al.Estimation of the effect of nonisotropically distributed energy on the apparent arrival time in correlations[M].Geophysics,2010,75(5):SA85-SA93.
[30]Ratdomopurbo A,Poupinet G.Monitoring a temporal change of seismic velocity in a volcano:Application to the 1992 eruption of Mt.Merapi(Indonesia)[J].Geophysical Research Letters,1995,22(7):775-778.
[31]Clarke D,Zaccarelli L,Shapiro N M,et.al.Assessment of resolution and accuracy of the Moving Window Cross Spectral technique for monitoring crustal temporal variations using ambient seismic noise[J].Geophysical Journal International.2011,186:867-882.
[32]Liu Z K,Huang J L,Li J J.Comparison of four techniques for estimating temporal change of seismic velocity with passive image interferometry[J].Earthquake Science,2010,23:511-518.
[33]赵盼盼,陈九辉,刘启元,等.汶川地震区地壳速度相对变化的环境噪声自相关研究[J].地球物理学报,2012,55(1):137-145.
[34]付芮,单斌,熊熊,等.2014年云南鲁甸地震同震库仑应力对余震分布及周边断层的影响[J].地震地质,2015,37(4):1084-1095.
[2]刘成利,郑勇,熊熊,等.利用区域宽频带数据反演鲁甸Ms6.5地震震源破裂过程[J].地球物理学报,2014,57(9):3028-3037.
[3]徐锡伟,闻学泽,郑荣章,等.川滇地区活动块体最新构造变动样式及其动力来源[J].中国科学:D辑,2003,33(B04):151-162.
[4]Xu Z J,Song X D.Temporal changes of surface wave velocity associated with major Sumatra earthquakes from ambient noise correlation[J].PNAS,2009,106(34):14 207-14 212.
[5]Poupinet G,Ellsworth W L,Frechet J.Monitoring velocity variation in the crust using earthquake doublets:An application to Calaveras fault,California[J].Journal of Geophysical Research,1984,89(B7):5 719-5 731.
[6]Ratdomopurbo A,Poupinet G.Monitoring a temporal changes of seismic velocity in a colcano:Application to the 1992 eruption of Mt.Merapi(Indoesia)[J].Geophysical Research Letters,1995,22(7):775-778.
[7]Peng Z,Ben-Zion Y.Temporal changes of shallow seismic velocity around the Karadere-Duzce branch of the North Anatolian Fault and strong ground motion[J].Pure and Applied Geophysics,2006,163:567-600.
[8]Nishimura T,Uchida N,Sato H,et al.Temporal changes of the crustal structure associated with the M6.1 earthquake on September 3,1998 and the volcanic activity of mount Iwate,Japan[J].Geophysical Research Letters,2000,27(2):269-272.
[9]Niu F L,Silver P G,Daley T M,et al.Preseismic velocity changes observed from active source monitoring at the Parkfield SAFOD drill site[J].Nature,2008,454:204-244.
[10]Stehly L,Froment B,Campillo M,et al.Monitoring seismic wave velocity changes associated with the MW7.9 Wenchuan earthquake:Increasing the temporal resolution using curvelet filters[J].Geophysical Journal International,2015,201:1 939-1 949.
[11]Weaver R L,Lobkis O I.Ultrasonics without a source:Thermal fluctuation correlation at MHz frequencies[J].Physical Review Letters,2001a,87.
[12]Weaver R L,Lobkis O I.On the emergence of the Green’s function in the correlations of a diffuse field[J].2001b,Acoustical Society of America,110:3011-3017.
[13]Derode A,Larose E,Tanter M,et al.Recovering the Green’s function from field-field correlation in an open scattering medium[J].Acoustical Society of America,2003,113:2 973-2 976.
[14]Campillo M,Paul A.Long-range correlations in the diffuse seismic coda[J].Science,2003,299(5606):547-549.
[15]Shapiro N M,Campillo M.Emergence of broadband Rayleigh waves from correlations of the ambient seismic noise[J].Geophysical Research Letters,2004,31:L07614.
[16]Brenguier F,Campillo M,Hadziioannou C,et al.Postseismic relaxation along the San Andreas fault at Parkfield from continuous seismological observations[J].Science,2009,321:1 478-1 481.
[17]Sens-Schnfelder C,Wegler U.Passive image interferometry and seasonal variations of seismic velocities at Merapi Volcano,Indonesia[J].Geophysical Research Letters,2006,33:L21302.
[18]Wegler U,Sens-Schnfelder C.Fault zone monitoring with passive image interferometry[J].Geophysical Journal International,2007,168:1 029-1 033.
[19]Brenguier F,Shapiro N M,Campillo M,et al.2008.Towards forecasting volcanic eruptions using seismic noise[J].Nature Geoscience,1:126-130.
[20]刘志坤,黄金莉.利用背景噪声互相关研究汶川地震震源区地震波速度变化[J].地球物理学报,2010,53(04):853-863.
[21]Chen J H,Froment B,Liu Q Y,et al.Distribution of seismic wave speed changes associated with the 12May 2008 MW7.9 Wenchuan earthquake[J].Geophysical Research Letters,2010,37:L18302.
[22]Brenguier F,Clarke D,Aoki Y,et al.Monitoring volcanoes using seismic noise correlations[J].Comptes Rendus Geoscience,2011,343:633-638.
[23]Froment B,Campillo M,Chen J H,et al.Deformation at depth associated with the May 12,2008 MW7.9 Wenchuan earthquake from seismic ambient noise monitoring[J].Geophysical Research Letters,2013,40:78-82.
[24]Brenguier F,Campillo M,Takeda T,et al.Mapping pressurized volcanic fluids from induced crustal seismic velocity drops[J].Science,2014,345:80-82.
[25]Sawazaki K,Kimura H,Shiomi K,et al.Depth-dependence of seismic velocity change associated with the2011 Tohoku earthquake,Japan,revealed from repeating earthquake analysis and finite-difference wave propagation simulation[J].Geophysical Journal International,2015,201:741-763.
[26]Lecocq T,Caudron C,Brenguier F.2014.MSNoise,a python package for monitoring seismic velocity changes using ambient seismic noise[J].Geophysical Research Letters,85(3):715-726.
[27]Bensen G D,Ritzwoller M H,Barmin M P,et al.Processing seismic ambient noise data to obtain reliable broad-band surface wave dispersion measurements[J].Geophysical Journal International,2007,169:1 239-1 260.
[28]Stehly L,Campillo M,Shapiro N M.A study of the seismic noise from its long-range correlation properties[J].Journal of Geophysical Research,2006,111:B10303.
[29]Froment B,Campillo M,Roux P,et al.Estimation of the effect of nonisotropically distributed energy on the apparent arrival time in correlations[M].Geophysics,2010,75(5):SA85-SA93.
[30]Ratdomopurbo A,Poupinet G.Monitoring a temporal change of seismic velocity in a volcano:Application to the 1992 eruption of Mt.Merapi(Indonesia)[J].Geophysical Research Letters,1995,22(7):775-778.
[31]Clarke D,Zaccarelli L,Shapiro N M,et.al.Assessment of resolution and accuracy of the Moving Window Cross Spectral technique for monitoring crustal temporal variations using ambient seismic noise[J].Geophysical Journal International.2011,186:867-882.
[32]Liu Z K,Huang J L,Li J J.Comparison of four techniques for estimating temporal change of seismic velocity with passive image interferometry[J].Earthquake Science,2010,23:511-518.
[33]赵盼盼,陈九辉,刘启元,等.汶川地震区地壳速度相对变化的环境噪声自相关研究[J].地球物理学报,2012,55(1):137-145.
[34]付芮,单斌,熊熊,等.2014年云南鲁甸地震同震库仑应力对余震分布及周边断层的影响[J].地震地质,2015,37(4):1084-1095.