超导重力仪检测2011年日本东北M_w9.0级地震前的重力扰动信号
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摘要
对大地震前的扰动现象的研究有助于认识地震孕育的动力学过程,震前重力扰动已成为关注的热点之一.对大地震前的扰动现象的研究有助于认识地震孕育的动力学过程,震前重力扰动已成为关注的热点之一.为检验日本Mw9.0级地震是否存在震前扰动现象,本研究利用全球超导重力仪记录到的地震前后7天内20组秒采样数据进行分析.经潮汐、大气改正等处理去除仪器的漂移及残余潮汐效应,得到非潮汐重力变化曲线.结果表明大部分振幅大于30×10-8 m.s-2的曲线反映了全球Mw≥6级地震引起的高频波动信号,其中11组数据在3月9日Mw7.3级前震之前出现了扰动现象.震前扰动可分解为三个频段,其中,低于0.1Hz和高于0.18Hz的分量分别反映了地震波动信号及非构造信息,中间频段(0.118～0.18Hz)信号能够较大程度地压制地震波动信号、并同时保留异常扰动信息.它的振幅在3月7日10时之前基本保持约1×10-8 m.s-2,之后开始逐渐增大,到3月9日7.3级前震前后达到最大,此后振荡衰减,振幅保持约(5～10)×10-8 m.s-2,直至主震发生.中间频段信号的变化特征与主震前的应力迁移过程以及实验记录到的地震成核过程有许多相似之处;不过,震前重力异常是否与主震前的应力加速积累有关,仍待进一步研究.
The investigation on pre-seismic anomalies prior to big earthquakes will give insights into the dynamic processes of the nucleation/development of the earthquakes;the pre-seismic gravity anomalies have become one of the most focused phenomena.In order to examine if anomalies did present prior to the Mw 9.0 earthquake that occurred on March 11,2011,in Japan,we analyzed 7-day-long 1 Hz sampling records from 20 superconducting gravimeters(SG) worldwide.We obtained the non-tidal gravity change time series by removing the solid tides and the pressure effect as well as the drift.Most of the non-tidal gravity changes with amplitude larger than 30×10-8 m·s-2 were associated with Mw≥6 earthquakes worldwide;pre-seismic anomalies presented in 11 SGs data before the Mw7.3 foreshock.The pre-seismic anomalies can be decomposed into three frequencies,among which the earthquake-related and non-tectonic signals are constrained on the frequencies less than 0.1Hz and larger than 0.18Hz,respectively;whereas the signal of medium frequencies(0.118~0.18 Hz) can maintain the anomalies while suppress the earthquake-related signal.The amplitudes of the medium frequency signal increased gradually from ~1×10-8 m·s-2 at 10:00,7 March,to peaks larger than ~10×10-8 m·s-2 when the largest foreshock(Mw7.3) occurred on 9 March,subsequently the amplitudes fluctuated and decreased to about(5~10)×10-8 m·s-2 and kept the same level until the main shock.Such evolution is similar to the stress migration before the mainshock as well as the nucleation processes recorded in rock rupture experiments;nevertheless it need further study to test if the pre-seismic gravity anomaly is related to the accelerating stress accumulation before the main shock.
The investigation on pre-seismic anomalies prior to big earthquakes will give insights into the dynamic processes of the nucleation/development of the earthquakes;the pre-seismic gravity anomalies have become one of the most focused phenomena.In order to examine if anomalies did present prior to the Mw 9.0 earthquake that occurred on March 11,2011,in Japan,we analyzed 7-day-long 1 Hz sampling records from 20 superconducting gravimeters(SG) worldwide.We obtained the non-tidal gravity change time series by removing the solid tides and the pressure effect as well as the drift.Most of the non-tidal gravity changes with amplitude larger than 30×10-8 m·s-2 were associated with Mw≥6 earthquakes worldwide;pre-seismic anomalies presented in 11 SGs data before the Mw7.3 foreshock.The pre-seismic anomalies can be decomposed into three frequencies,among which the earthquake-related and non-tectonic signals are constrained on the frequencies less than 0.1Hz and larger than 0.18Hz,respectively;whereas the signal of medium frequencies(0.118~0.18 Hz) can maintain the anomalies while suppress the earthquake-related signal.The amplitudes of the medium frequency signal increased gradually from ~1×10-8 m·s-2 at 10:00,7 March,to peaks larger than ~10×10-8 m·s-2 when the largest foreshock(Mw7.3) occurred on 9 March,subsequently the amplitudes fluctuated and decreased to about(5~10)×10-8 m·s-2 and kept the same level until the main shock.Such evolution is similar to the stress migration before the mainshock as well as the nucleation processes recorded in rock rupture experiments;nevertheless it need further study to test if the pre-seismic gravity anomaly is related to the accelerating stress accumulation before the main shock.
引文
[1]Hinderer J,Crossley D,Warburton R.Gravimetric methods-superconducting gravity meters.In:Schubert G,eds.Treatise on Geophysics,2007,3:65-122.
[2]Imanishi Y,Sato T,Higashi T,et al.A network ofsuperconducting gravimeters detects submicrogal coseismicgravity changes.Science,2004,306(5695):476-478.
[3]Hwang C,Kao R,Cheng C C,et al.Results from parallelobservations of superconducting and absolute gravimeters andGPS at the Hsinchu station of Global Geodynamics Project,Taiwan.J.Geophys.Res.,2009,114(B07406),doi:10.1029/2008JB006195.
[4]王武星,马丽,黄建平.强地震前后重力观测中异常变化现象的研究.地震,2007,27(2):53-63.Wang W X,Ma L,Huang J P.Analysis of anomaly ingravity observation before and after strong earthquakes.Earthquake(in Chinese),2007,27(2):53-63.
[5]郝晓光,胡小刚.宽带地震仪资料证实汶川大地震“震前重力扰动”.地球物理学进展,2008,23(4):1332-1335.Hao X G,Hu X G.Disturbance before the Wenchuanearthquake detected by broadband seismometer.Progress inGeophysics(in Chinese),2008,23(4):1332-1335.
[6]郝晓光,胡小刚.“震前扰动”现象:从模糊走向清晰-与傅容珊教授商榷.地球物理学进展,2011,26(6):2255-2261.Hao X G,Hu X G.Pre-earthquake-tremor maze,fromconfusing to gradually crystal-answer to the comment byProfessor Fu Rong-Shang on“The short-term anomaliesdetected by broadband seismographs before the May 12Wenchuan earthquake,Sichuan,China”.Progress inGeophysics(in Chinese),2011,26(6):2255-2261.
[7]Shen W B,Wang D J,Hwang C.Anomalous signals prior toWenchuan earthquake detected by superconducting gravimeter andbroadband seismometers records.J.Earth Sci.,2011,22(5):640-651.
[8]Lan S C,Yu T T,Hwang C,et al.An analysis of mechanicalconstraints when using superconducting gravimeters for far-fieldpre-seismic anomaly detection.Terr.Atmos.Ocean.Sci.,2011,22(3):271-282.
[9]韦进,郝洪涛,康开轩等.汶川地震前成都台重力的高频扰动.大地测量与地球动力学,2009,29(增刊):15-19,24.Wei J,Hao H T,Kang K X,et al.Gravity disturbance ofhigh frequency at Chengdu seismostation before WenchuanMs8.0earthquake.J.Geodesy Geody.(in Chinese),2009,29(Supp.1):15-19,24.
[10]张雁滨,蒋骏,廖盈春等.宽频地震计及倾斜、重力仪对长周期波动信号的综合观测.地震学报,2008,30(6):626-633.Zhang Y B,Jiang J,Liao Y C,et al.Joint observation oflong period seismic signals with broadband seismometer,tiltmeter and gravimeter.Acta Seismologica Sinica(inChinese),2008,30(6):626-633.
[11]刘子维,韦进,郝洪涛等.日本Ms9.0地震前的重力高频扰动.大地测量与地球动力学,2011,31(2):4-8.Liu Z W,Wei J,Hao H T,et al.Pre-seismic gravitydisturbance of high frequency before Ms9.0earthquake inJapan.J.Geodesy Geod.(in Chinese),2011,31(2):4-8.
[12]韦进,刘子维,郝洪涛等.日本Ms9.0地震前的连续重力观测异常.大地测量与地球动力学,2011,31(2):9-11,16.Wei J,Liu Z W,Hao H T,et al.Gravity anomalies in beforeMs9.0earthquake in Japan observed by continuous relativegravimeter in China.J.Geodesy Geody.(in Chinese),2011,31(2):9-11,16.
[13]Van Camp M,Vauterin P.Tsoft:graphical and interactivesoftware for the analysis of time series and Earth tides.Computers&Geosciences,2005,31(5):631-640.
[14]Wenzel H G.The nanogal software:Earth tide dataprocessing package ETERNA 3.30.Bull.Inf.MaréesTerrestres,1996,124:9425-9439.
[15]Banka D,Crossley D.Noise levels of superconductinggravimeters at seismic frequencies.Geophys.J.Int.,1999,139(1):87-97.
[16]Xi Q W.A new complete development of the tide-generatingpotential for the epoch J2000.0.Bull.Inf.Marées Terrestres,1989,99:6766-6812.
[17]郝晓光,胡小刚.汶川大地震“震前扰动”存在“第三类脉动”吗?地球物理学进展,2009,24(4):1213-1215.Hao X G,Hu X G.Are‘third microseisms’in anomaloustremor before the great Wenchuan earthquake?Progress inGeophysics(in Chinese),2009,24(4):1213-1215.
[18]胡小刚,郝晓光,薛秀秀.汶川大地震前非台风扰动现象的研究.地球物理学报,2010,53(12):2875-2886.Hu X G,Hao X G,Xue X X.The analysis of the non-typhoon-induced microseisms before the 2008 Wenchuanearthquake.Chinese J.Geophys.(in Chinese),2010,53(12):2875-2886.
[19]Woodhouse J H,Deuss A.Theory and observation-Earth′sfree oscillations.In:Schubert G,eds.Treatise on Geophysics,2007,1:31-65.
[20]Farrell W E.Deformation of the Earth by surface loads.Rev.Geophys.,1972,10(3):761-797.
[21]Kusche J,Schrama E J O.Surface mass redistributioninversion from global GPS deformation and Gravity Recoveryand Climate Experiment(GRACE)gravity data.J.Geophys.Res.,2005,110(B09409),doi:10.1029/2004JB003556.
[22]韦进,李辉,刘子维等.利用积谱研究气压对SGC053超导重力仪的影响.大地测量与地球动力学,2011,31(4):47-51.Wei J,Li H,Liu Z W,et al.Study on influence of pressureon gravimeter SGC053by use of product spectra.J.GeodesyGeod.(in Chinese),2011,31(4):47-51.
[23]Klein Tank A M G,Wijngaard J B,Knnen G P,et al.Dailydataset of 20th-century surface air temperature andprecipitation series for the European Climate Assessment.Int.J.Climatol.,2002,22(12):1441-1453.
[24]Longuet-Higgins M S.A theory of the origin of microseisms.Philos.Trans.R.Soc.London,Ser.A,1950,243(857):1-35.
[25]Liu C C,Linde A L,Selwyn Sacks I.Slow earthquakestriggered by typhoons.Nature,2009,459(7248):833-836.
[26]Tanimoto T.Excitation of microseisms.Geophys.Res.Lett.,2007,34(L05308),doi:10.1029/2006GL029046.
[27]Kato A,Obara K,Igarashi T,et al.Propagation of slow slipleading up to the 2011 Mw9.0 Tohoku-Oki earthquake.Science,2012,335(6069):705-708.
[28]Papadimitriou P.Identification of seismic precursors beforelarge earthquakes:Decelerating and accelerating seismicpatterns.J.Geophys.Res.,2008,113(B04306),doi:10.1029/2007JB005112.
[29]Suito H,Nishimura T,Tobita M,et al.Interplate fault slipalong the Japan Trench before the occurrence of the 2011offthe Pacific coast of Tohoku earthquake as inferred from GPSdata.Earth Planets Space,2011,63(7):615-619.
[30]Hori T,Miyazaki S.A possible mechanism of M9earthquakegeneration cycles in the area of repeating M7～8earthquakessurrounded by aseismic sliding.Earth Planets Space,2011,63(7):773-777.
[31]Miyazaki S,McGuire J J,Segall P.Seismic and aseismic faultslip before and during the 2011off the Pacific coast of Tohokuearthquake.Earth Planets Space,2011,63(7):637-642.
[32]马胜利,雷兴林,刘力强.标本非均匀性对岩石变形声发射时空分布的影响及其地震学意义.地球物理学报,2004,47(1):127-131.Ma S L,Lei X L,Liu L Q.Effects of heterogeneity in rocksamples on spatial and temporal distribution of acousticemission and their significance in seismology.Chinese J.Geophys.(in Chinese),2004,47(1):127-131.
[33]马瑾,刘力强,刘培洵等.断层失稳错动热场前兆模式:雁列断层的实验研究.地球物理学报,2007,50(4):1141-1149.Ma J,Liu L Q,Liu P X,et al.Thermal precursory patternof fault unstable sliding:An experimental study of en echelonfaults.Chinese J.Geophys.(in Chinese),2007,50(4):1141-1149.
[34]马瑾,Sherman S I,郭彦双.地震前亚失稳应力状态的识别—以5°拐折断层变形温度场演化的实验为例.中国科学:地球科学,2012,42(5):633-645.Ma J,Sherman S I,Guo Y S.Identification of meta-stablestress state based on experimental study of evolution of thetemperature field during stick-slip instability on a 5°bendingfault.Sci China Earth Sci.(in Chinese),2012,55(6):869-881.
[35]马瑾,马胜利,刘力强等.断层几何结构与物理场的演化及失稳特征.地震学报,1996,18(2):200-207.Ma J,Ma S L,Liu L Q,et al.Physical field evolution andinstability properties of fault geometry.Acta SeismologicaSinica(in Chinese),1996,18(2):200-207.
[36]Liu L Q,Ma S L,Ma J,et al.Effect of rock structure onstatistical characteristics of acoustic emission.EarthquakeResearch in China,1999,13(3):355-366.
[37]许昭永,王彬,胡毅力等.试论岩石破裂和破坏的差异对地震模拟及前兆研究的影响.地球物理学报,2009,52(3):712-719.Xu Z Y,Wang B,Hu Y L,et al.A discussion on theinfluence of the difference between the rock fracture andfailure to the earthquake simulation and the precursorstudies.Chinese J.Geophys.(in Chinese),2009,52(3):712-719.
[2]Imanishi Y,Sato T,Higashi T,et al.A network ofsuperconducting gravimeters detects submicrogal coseismicgravity changes.Science,2004,306(5695):476-478.
[3]Hwang C,Kao R,Cheng C C,et al.Results from parallelobservations of superconducting and absolute gravimeters andGPS at the Hsinchu station of Global Geodynamics Project,Taiwan.J.Geophys.Res.,2009,114(B07406),doi:10.1029/2008JB006195.
[4]王武星,马丽,黄建平.强地震前后重力观测中异常变化现象的研究.地震,2007,27(2):53-63.Wang W X,Ma L,Huang J P.Analysis of anomaly ingravity observation before and after strong earthquakes.Earthquake(in Chinese),2007,27(2):53-63.
[5]郝晓光,胡小刚.宽带地震仪资料证实汶川大地震“震前重力扰动”.地球物理学进展,2008,23(4):1332-1335.Hao X G,Hu X G.Disturbance before the Wenchuanearthquake detected by broadband seismometer.Progress inGeophysics(in Chinese),2008,23(4):1332-1335.
[6]郝晓光,胡小刚.“震前扰动”现象:从模糊走向清晰-与傅容珊教授商榷.地球物理学进展,2011,26(6):2255-2261.Hao X G,Hu X G.Pre-earthquake-tremor maze,fromconfusing to gradually crystal-answer to the comment byProfessor Fu Rong-Shang on“The short-term anomaliesdetected by broadband seismographs before the May 12Wenchuan earthquake,Sichuan,China”.Progress inGeophysics(in Chinese),2011,26(6):2255-2261.
[7]Shen W B,Wang D J,Hwang C.Anomalous signals prior toWenchuan earthquake detected by superconducting gravimeter andbroadband seismometers records.J.Earth Sci.,2011,22(5):640-651.
[8]Lan S C,Yu T T,Hwang C,et al.An analysis of mechanicalconstraints when using superconducting gravimeters for far-fieldpre-seismic anomaly detection.Terr.Atmos.Ocean.Sci.,2011,22(3):271-282.
[9]韦进,郝洪涛,康开轩等.汶川地震前成都台重力的高频扰动.大地测量与地球动力学,2009,29(增刊):15-19,24.Wei J,Hao H T,Kang K X,et al.Gravity disturbance ofhigh frequency at Chengdu seismostation before WenchuanMs8.0earthquake.J.Geodesy Geody.(in Chinese),2009,29(Supp.1):15-19,24.
[10]张雁滨,蒋骏,廖盈春等.宽频地震计及倾斜、重力仪对长周期波动信号的综合观测.地震学报,2008,30(6):626-633.Zhang Y B,Jiang J,Liao Y C,et al.Joint observation oflong period seismic signals with broadband seismometer,tiltmeter and gravimeter.Acta Seismologica Sinica(inChinese),2008,30(6):626-633.
[11]刘子维,韦进,郝洪涛等.日本Ms9.0地震前的重力高频扰动.大地测量与地球动力学,2011,31(2):4-8.Liu Z W,Wei J,Hao H T,et al.Pre-seismic gravitydisturbance of high frequency before Ms9.0earthquake inJapan.J.Geodesy Geod.(in Chinese),2011,31(2):4-8.
[12]韦进,刘子维,郝洪涛等.日本Ms9.0地震前的连续重力观测异常.大地测量与地球动力学,2011,31(2):9-11,16.Wei J,Liu Z W,Hao H T,et al.Gravity anomalies in beforeMs9.0earthquake in Japan observed by continuous relativegravimeter in China.J.Geodesy Geody.(in Chinese),2011,31(2):9-11,16.
[13]Van Camp M,Vauterin P.Tsoft:graphical and interactivesoftware for the analysis of time series and Earth tides.Computers&Geosciences,2005,31(5):631-640.
[14]Wenzel H G.The nanogal software:Earth tide dataprocessing package ETERNA 3.30.Bull.Inf.MaréesTerrestres,1996,124:9425-9439.
[15]Banka D,Crossley D.Noise levels of superconductinggravimeters at seismic frequencies.Geophys.J.Int.,1999,139(1):87-97.
[16]Xi Q W.A new complete development of the tide-generatingpotential for the epoch J2000.0.Bull.Inf.Marées Terrestres,1989,99:6766-6812.
[17]郝晓光,胡小刚.汶川大地震“震前扰动”存在“第三类脉动”吗?地球物理学进展,2009,24(4):1213-1215.Hao X G,Hu X G.Are‘third microseisms’in anomaloustremor before the great Wenchuan earthquake?Progress inGeophysics(in Chinese),2009,24(4):1213-1215.
[18]胡小刚,郝晓光,薛秀秀.汶川大地震前非台风扰动现象的研究.地球物理学报,2010,53(12):2875-2886.Hu X G,Hao X G,Xue X X.The analysis of the non-typhoon-induced microseisms before the 2008 Wenchuanearthquake.Chinese J.Geophys.(in Chinese),2010,53(12):2875-2886.
[19]Woodhouse J H,Deuss A.Theory and observation-Earth′sfree oscillations.In:Schubert G,eds.Treatise on Geophysics,2007,1:31-65.
[20]Farrell W E.Deformation of the Earth by surface loads.Rev.Geophys.,1972,10(3):761-797.
[21]Kusche J,Schrama E J O.Surface mass redistributioninversion from global GPS deformation and Gravity Recoveryand Climate Experiment(GRACE)gravity data.J.Geophys.Res.,2005,110(B09409),doi:10.1029/2004JB003556.
[22]韦进,李辉,刘子维等.利用积谱研究气压对SGC053超导重力仪的影响.大地测量与地球动力学,2011,31(4):47-51.Wei J,Li H,Liu Z W,et al.Study on influence of pressureon gravimeter SGC053by use of product spectra.J.GeodesyGeod.(in Chinese),2011,31(4):47-51.
[23]Klein Tank A M G,Wijngaard J B,Knnen G P,et al.Dailydataset of 20th-century surface air temperature andprecipitation series for the European Climate Assessment.Int.J.Climatol.,2002,22(12):1441-1453.
[24]Longuet-Higgins M S.A theory of the origin of microseisms.Philos.Trans.R.Soc.London,Ser.A,1950,243(857):1-35.
[25]Liu C C,Linde A L,Selwyn Sacks I.Slow earthquakestriggered by typhoons.Nature,2009,459(7248):833-836.
[26]Tanimoto T.Excitation of microseisms.Geophys.Res.Lett.,2007,34(L05308),doi:10.1029/2006GL029046.
[27]Kato A,Obara K,Igarashi T,et al.Propagation of slow slipleading up to the 2011 Mw9.0 Tohoku-Oki earthquake.Science,2012,335(6069):705-708.
[28]Papadimitriou P.Identification of seismic precursors beforelarge earthquakes:Decelerating and accelerating seismicpatterns.J.Geophys.Res.,2008,113(B04306),doi:10.1029/2007JB005112.
[29]Suito H,Nishimura T,Tobita M,et al.Interplate fault slipalong the Japan Trench before the occurrence of the 2011offthe Pacific coast of Tohoku earthquake as inferred from GPSdata.Earth Planets Space,2011,63(7):615-619.
[30]Hori T,Miyazaki S.A possible mechanism of M9earthquakegeneration cycles in the area of repeating M7～8earthquakessurrounded by aseismic sliding.Earth Planets Space,2011,63(7):773-777.
[31]Miyazaki S,McGuire J J,Segall P.Seismic and aseismic faultslip before and during the 2011off the Pacific coast of Tohokuearthquake.Earth Planets Space,2011,63(7):637-642.
[32]马胜利,雷兴林,刘力强.标本非均匀性对岩石变形声发射时空分布的影响及其地震学意义.地球物理学报,2004,47(1):127-131.Ma S L,Lei X L,Liu L Q.Effects of heterogeneity in rocksamples on spatial and temporal distribution of acousticemission and their significance in seismology.Chinese J.Geophys.(in Chinese),2004,47(1):127-131.
[33]马瑾,刘力强,刘培洵等.断层失稳错动热场前兆模式:雁列断层的实验研究.地球物理学报,2007,50(4):1141-1149.Ma J,Liu L Q,Liu P X,et al.Thermal precursory patternof fault unstable sliding:An experimental study of en echelonfaults.Chinese J.Geophys.(in Chinese),2007,50(4):1141-1149.
[34]马瑾,Sherman S I,郭彦双.地震前亚失稳应力状态的识别—以5°拐折断层变形温度场演化的实验为例.中国科学:地球科学,2012,42(5):633-645.Ma J,Sherman S I,Guo Y S.Identification of meta-stablestress state based on experimental study of evolution of thetemperature field during stick-slip instability on a 5°bendingfault.Sci China Earth Sci.(in Chinese),2012,55(6):869-881.
[35]马瑾,马胜利,刘力强等.断层几何结构与物理场的演化及失稳特征.地震学报,1996,18(2):200-207.Ma J,Ma S L,Liu L Q,et al.Physical field evolution andinstability properties of fault geometry.Acta SeismologicaSinica(in Chinese),1996,18(2):200-207.
[36]Liu L Q,Ma S L,Ma J,et al.Effect of rock structure onstatistical characteristics of acoustic emission.EarthquakeResearch in China,1999,13(3):355-366.
[37]许昭永,王彬,胡毅力等.试论岩石破裂和破坏的差异对地震模拟及前兆研究的影响.地球物理学报,2009,52(3):712-719.Xu Z Y,Wang B,Hu Y L,et al.A discussion on theinfluence of the difference between the rock fracture andfailure to the earthquake simulation and the precursorstudies.Chinese J.Geophys.(in Chinese),2009,52(3):712-719.
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