中小地震宽频带辐射能量的单台测定
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摘要
辐射能量是独立于地震矩的另一个重要的震源参数 ,在地震危险性和地震危害的评估工作中具有重要的实际意义。通过辐射能量和地震矩的比较可以估计视应力 ,而视应力是震源物理研究中一个重要的物理量。考虑到我国地震台网分布不均匀的情况 ,本文尝试利用单台宽频带波形资料进行辐射能量的测定。选用CDSN昆明台 (KMI)记录的中小地震宽频带波形资料 ,分析地震图横向分量上的SH波及其后续震相 ,采用哈佛大学的震源机制结果进行辐射花样因子的校正 ,通过采用Brune模型 ,用补偿谱的方法试错得到品质因子Q。所得结果与NEIC用远震体波测得的能量结果具有较好的一致性。用同样的方法 ,还对更小的地震进行了能量测定的尝试 ,结果表明小地震的视应力 -地震矩标度关系似乎与中强震有所不同。
Radiated energy of an earthquake is an important source parameter independent of seismic moment. Radiated energy is often related to the potential for destruction which is crucial in the study of seismic risk. Besides, measurement of radiated energy of small to moderate earthquakes, together with the measurement of seismic moment, may give the estimate of apparent stress which is shown to be useful in the physics of seismic source. Due to the sparse distribution of seismological stations, analysis of seismograms at a single station for the measurement of radiated energy plays an important role for the regions in developing countries such as China. In this study, we take the CDSN Kunming station (KMI) in Yunnan Province as an example, focusing on the small to moderate events recorded by this station at local to regional distances, within 10° around the station. Broadband (BB or IP) seismograms of the transverse component are used. The main ingredients of seismic phases considered are basically the mixture of reverberating SH waves, Love modes, and scattered coda. Focal mechanisms from the Harvard CMT catalogue are taken for the correction of the azimuth-dependence of radiation pattern. Q-value along the source-to-station path is obtained by assuming a Brune omega-square source model. Integration in the frequency domain is taken for the estimate of energy flux. Calculation results are compared with the measurements of NEIC which uses teleseismic body waveforms, and show good agreement. Measurement is then extended to even smaller events. It is found that energy-M L relations for small earthquakes and for moderate earthquakes are different.
Radiated energy of an earthquake is an important source parameter independent of seismic moment. Radiated energy is often related to the potential for destruction which is crucial in the study of seismic risk. Besides, measurement of radiated energy of small to moderate earthquakes, together with the measurement of seismic moment, may give the estimate of apparent stress which is shown to be useful in the physics of seismic source. Due to the sparse distribution of seismological stations, analysis of seismograms at a single station for the measurement of radiated energy plays an important role for the regions in developing countries such as China. In this study, we take the CDSN Kunming station (KMI) in Yunnan Province as an example, focusing on the small to moderate events recorded by this station at local to regional distances, within 10° around the station. Broadband (BB or IP) seismograms of the transverse component are used. The main ingredients of seismic phases considered are basically the mixture of reverberating SH waves, Love modes, and scattered coda. Focal mechanisms from the Harvard CMT catalogue are taken for the correction of the azimuth-dependence of radiation pattern. Q-value along the source-to-station path is obtained by assuming a Brune omega-square source model. Integration in the frequency domain is taken for the estimate of energy flux. Calculation results are compared with the measurements of NEIC which uses teleseismic body waveforms, and show good agreement. Measurement is then extended to even smaller events. It is found that energy-M L relations for small earthquakes and for moderate earthquakes are different.
引文
陈培善,Duda,S .J .,1993.由CDSN记录计算出的谱震级和地震辐射能.地震学报,15(4):418～426。
陈学忠、王小平、王林瑛、张天中,2003.地震视应力用于震后趋势快速判定的可能性.国际地震动态,(7):1～4。
刘瑞丰、吴忠良、阴朝民、陈运泰、庄灿涛,2003.中国地震台网数字化改造的进展.地震学报,25(5):535～540。
吴建平,2001.云南数字地震台站下方的S波速度结构研究.地球物理学报,44(2):228～237。
吴忠良、陈运泰、Mozaffari,P .,1999.应力降的标度性质与震源谱高频衰减常数.地震学报,21(5):460～468。
Boatwright,J.andBoore,D .M .,1982.Analysisofgroundaccelerationsradiatedbythe1980LivermoreValleyearthquakesfordirectivityanddynamicsourcecharacteristics.Bull.Seism.Soc.Amer.,70:1843～1865.
Boatwright,J.andChoy,G .L .,1986.Teleseismicestimatesoftheenergyradiatedbyshallowearthquakes.J.Geophys.Res.,91:2095～2112.
Boatwright,J.,Choy,G .L .andSeekins,L .C .,2002.Regionalestimatesofradiatedseismicenergy.Bull.Seism.Soc.Amer.,92:1241～1255.
Boatwright,J .andFletcher,J .B .,1987.ThepartitionofradiatedenergybetweenPandSwave.Bull.Seism.Soc.Amer.,77:361～376.
Brune,J.N .,1970.Tectonicstressandspectraofseismicsharewavefromearthquake.J.GeophysRes.,75:4997～5009.
Brune,J.N .,1971.Correction.J .Geophys.Res.,76:5002.
Choy,G .L .andBoatwright,J .,1995.Globalpatternsofradiatedseismicenergyandapparentstress.J .Geophys.Res.,100:18205～18228.
Duda,S .J .andNortmann,R .,1983.Normal,blueandredearthquakesAnewwayofearthquakeclassificationonthebasisofbody wavemagnitudes,Tectonophysics,93:295～306.
Ide,S .andBeroza,G .C .,2001.Doesapparentstressvarywithearthquakesize?Geophys.Res.Lett.,28:3349～3352.
Izutani,Y .andKanamori,H .,2001.Scale dependenceofseismicenergy to momentratioforstrike slipearthquakesinJapan.Geophys.Res.Lett.,28:4007～4010.
Kanamori,H .,Anderson,D .L .andHeaton,T .H .,1998.Frictionalmeltingduringtheruptureofthe1994Bolivianearthquake.Science,279:839～842.
Kanamori,H .andHeaton,T .H .,2000.Microscopicandmacroscopicphysicsofearthquakes.In:Rundle,J.B .,Turcotte,D .L .andKlein,W .(eds.),GeoComplexityandthePhysicsofEarthquakes.Washington,D .C .:AGU 147～163.
Nortmann,R .andDuda,S .J .,1982.TheamplitudespectraofP andS waveandthebody wavemagnitudeofearthquakes.Tectonophysics,84:17～32.
Nortmann,R .andDuda,S .J .,1983.Determinationofspectralpropertiesofearthquakesfromtheirmagnitudes.Tectonophysics,93:251～275.
Wu,Z .L .,2000.Frequency sizedistributionofglobalseismicityseenfrombroadbandradiatedenergy.Geophys.J.Int.,142:59～66.
Wu,Z .L .,2001a.Earthquakescalingparadox.Chin.Phys.,10:395～397.
Wu,Z .L .,2001b.Scalingofapparentstressfrombroadbandradiatedenergycatalogueanditsfocalmechanismdependence.EarthPlanetsSpace,53:943～948
陈学忠、王小平、王林瑛、张天中,2003.地震视应力用于震后趋势快速判定的可能性.国际地震动态,(7):1～4。
刘瑞丰、吴忠良、阴朝民、陈运泰、庄灿涛,2003.中国地震台网数字化改造的进展.地震学报,25(5):535～540。
吴建平,2001.云南数字地震台站下方的S波速度结构研究.地球物理学报,44(2):228～237。
吴忠良、陈运泰、Mozaffari,P .,1999.应力降的标度性质与震源谱高频衰减常数.地震学报,21(5):460～468。
Boatwright,J.andBoore,D .M .,1982.Analysisofgroundaccelerationsradiatedbythe1980LivermoreValleyearthquakesfordirectivityanddynamicsourcecharacteristics.Bull.Seism.Soc.Amer.,70:1843～1865.
Boatwright,J.andChoy,G .L .,1986.Teleseismicestimatesoftheenergyradiatedbyshallowearthquakes.J.Geophys.Res.,91:2095～2112.
Boatwright,J.,Choy,G .L .andSeekins,L .C .,2002.Regionalestimatesofradiatedseismicenergy.Bull.Seism.Soc.Amer.,92:1241～1255.
Boatwright,J .andFletcher,J .B .,1987.ThepartitionofradiatedenergybetweenPandSwave.Bull.Seism.Soc.Amer.,77:361～376.
Brune,J.N .,1970.Tectonicstressandspectraofseismicsharewavefromearthquake.J.GeophysRes.,75:4997～5009.
Brune,J.N .,1971.Correction.J .Geophys.Res.,76:5002.
Choy,G .L .andBoatwright,J .,1995.Globalpatternsofradiatedseismicenergyandapparentstress.J .Geophys.Res.,100:18205～18228.
Duda,S .J .andNortmann,R .,1983.Normal,blueandredearthquakesAnewwayofearthquakeclassificationonthebasisofbody wavemagnitudes,Tectonophysics,93:295～306.
Ide,S .andBeroza,G .C .,2001.Doesapparentstressvarywithearthquakesize?Geophys.Res.Lett.,28:3349～3352.
Izutani,Y .andKanamori,H .,2001.Scale dependenceofseismicenergy to momentratioforstrike slipearthquakesinJapan.Geophys.Res.Lett.,28:4007～4010.
Kanamori,H .,Anderson,D .L .andHeaton,T .H .,1998.Frictionalmeltingduringtheruptureofthe1994Bolivianearthquake.Science,279:839～842.
Kanamori,H .andHeaton,T .H .,2000.Microscopicandmacroscopicphysicsofearthquakes.In:Rundle,J.B .,Turcotte,D .L .andKlein,W .(eds.),GeoComplexityandthePhysicsofEarthquakes.Washington,D .C .:AGU 147～163.
Nortmann,R .andDuda,S .J .,1982.TheamplitudespectraofP andS waveandthebody wavemagnitudeofearthquakes.Tectonophysics,84:17～32.
Nortmann,R .andDuda,S .J .,1983.Determinationofspectralpropertiesofearthquakesfromtheirmagnitudes.Tectonophysics,93:251～275.
Wu,Z .L .,2000.Frequency sizedistributionofglobalseismicityseenfrombroadbandradiatedenergy.Geophys.J.Int.,142:59～66.
Wu,Z .L .,2001a.Earthquakescalingparadox.Chin.Phys.,10:395～397.
Wu,Z .L .,2001b.Scalingofapparentstressfrombroadbandradiatedenergycatalogueanditsfocalmechanismdependence.EarthPlanetsSpace,53:943～948
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