核幔界面衍射波P_(diff)震相最大记录震中距探讨
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摘要
智利MS8.8特大地震在甘肃数字测震台网记录的最大震中距达179.7°,通过读取该地震初至震相的观测走时,计算该震相的平均观测慢度为4.104s/°,与Pdiff震相的理论慢度4.439s/°基本一致.研究结果表明:由于甘肃数字测震台网和甘东南野外观测流动台阵独特的地理位置,记录到了至今全球最大震中距(179.7°)的核幔界面衍射波Pdiff震相;Pdiff震相起始观测走时明显滞后于IASP91理论走时;核幔界面复杂的形态对不同方位传播的Pdiff震相观测走时产生了一定的影响.
The largest epicentral distance of Chile MS8.8 earthquake reaches179.7°recorded by Gansu Digital Seismic Network.Through artificially reading observational first-arrival travel time of the Chile earthquake,we calculated the average observational slowness of the first arrival phase is 4.104s/°,which is basically consistent with theoretical slowness(4.439s/°)of Pdiff.The results show that the Pdiffcan recorded at the epicentral distance 179.7°due to particular location of Gansu Digital Seismic Network and southeastern Gansu temporary observation array;the origin observed travel time lags behind the IASP91 theoretical travel time obviously;and Pdifftravel times observed from different directions are affected by complex morphology of the core-mantle boundary.
The largest epicentral distance of Chile MS8.8 earthquake reaches179.7°recorded by Gansu Digital Seismic Network.Through artificially reading observational first-arrival travel time of the Chile earthquake,we calculated the average observational slowness of the first arrival phase is 4.104s/°,which is basically consistent with theoretical slowness(4.439s/°)of Pdiff.The results show that the Pdiffcan recorded at the epicentral distance 179.7°due to particular location of Gansu Digital Seismic Network and southeastern Gansu temporary observation array;the origin observed travel time lags behind the IASP91 theoretical travel time obviously;and Pdifftravel times observed from different directions are affected by complex morphology of the core-mantle boundary.
引文
冯建刚,蒋长胜,韩立波,陈继锋.2012.甘肃测震台网监测能力及地震目录完整性分析[J].地震学报,34(5):646--658.Feng J G,Jiang C S,Han L B,Chen J F.2012.Analysis on the monitoring capability of seismic networks and completeness of earthquake catalogues in Gansu region[J].Acta Seismologica Sinica,34(5):646--658(in Chinese).
李克.2007.地震学与地震观测[M].北京:地震出版社:172.Li K.2007.Seismology and Earthquake Observation[M].Beijing:Seismological Press:172(in Chinese).
秦满忠,沈旭章,张元生,刘旭宙.2014.利用兰州小孔径地震台阵资料叠加观测走时曲线[J].地震学报,36(1):59--69.Qin M Z,Shen X Z,Zhang Y S,Liu X Z.2014.Observed travel-time curves by stacking records from Lanzhou smallaperture seismic array[J].Acta Seismologica Sinica,36(1):59--69(in Chinese).
唐群署,李丽红.2006.核幔边界D″区的地震学研究进展[J].地学前缘,13(2):213--223.Tang Q S,Li L H.2006.The Earth’s lowermost mantle and its seismological research progress[J].Earth Science Frontiers,13(2):213--223(in Chinese).
唐燕娟.1997.对P波衍射波Pdif震相记录范围的讨论[J].地震地磁观测与研究,18(2):32--36.Tang Y J.1997.A discussion on recorded distance for diffraction wave Pdif of wave P[J].Seismological and Geomagnetic Observation and Research,18(2):32--36(in Chinese).
许健生,隗永刚,张淑珍.2012.Pdif震相在CDSN兰州地震台的记录特征[J].西北地震学报,34(3):239--244.Xu J S,Wei Y G,Zhang S Z.2012.The recording characters of Pdif phase in seismic wave at CDSN Lanzhou seismic station[J].Northwestern Seismological Journal,34(3):239--244(in Chinese).
许健生,隗永刚,张淑珍.2013.Pdif波在中国CDSN台站的运动学特征[J].地震工程学报,35(3):610--617.Xu J S,Wei Y G,Zhang S Z.2013.The kinematic characteristics of Pdif-waves at CDSN stations[J].China EarthquakeEngineering Journal,35(3):610--617(in Chinese).
赵荣国.1987.中国763长周期台网观测到Δ=175.6°的幔-核界面衍射波[J].国际地震动态,(3):14--16.Zhao R G.1987.Waves diffracted at the mantle-core boundary observed by type-763long-period seismograph network ofChina[J].Recent Developments in World Seismology,(3):14--16(in Chinese).
Arthur R,John W.1993.Inference of core-mantle boundary topography from ISC PcP and PKP traveltimes[J].GeophysJ Int,115(3):991--1011.
Astiz L,Earle P,Shearer P.1996.Global stacking of broadband seismograms[J].Seismol Res Lett,67(4):8--18.
Helmberger D V,Wen L,Ding X.1998.Seismic evidence that the source of the Iceland hotspot lies at the core-mantleboundary[J].Nature,396(6708):251--255.
Labrosse S,Hernlund J W,Coltice N.2007.A crystallizing dense magma ocean at the base of the Earth’s mantle[J].Nature,450(7171):866--869.
McNamara A K,Garnero E J,Rost S.2010.Tracking deep mantle reservoirs with ultra-low velocity zones[J].EarthPlanet Sci Lett,299(1/2):1--9.
Mori J,Helmberger D V.1995.Localized boundary layer below the mid-Pacific velocity anomaly identified from a PcPprecursor[J].J Geophys Res,100(B10):20359--20365.
Rial J A.1978.On the focusing of seismic body waves at the epicentre’s antipode[J].Geophys J Int,55(3):737--743.
Rial J A,Cormier V F.1980.Seismic waves at the epicenter’s antipode[J].J Geophys Res,85(B5):2661--2668.
Soldati G,Boschi L,Piersanti A.2006.Global seismic tomography and modern parallel computers[J].Ann Geophys,49(4/5):977--986.
Sun D Y,Helmberger D V,Jackson J M,Clayton R W,Bower D J.2013.Rolling hills on the core-mantle boundary[J].Earth Planet Sci Lett,361:333--342.
Sze E K M,van der Hilst R D.2003.Core mantle boundary topography from short period PcP,PKP,and PKKP data[J].Physics Earth Planet Inter,135(1):27--46.
Wysession M E,Okal E A,Bina C R.1992.The structure of the core-mantle boundary from diffracted waves[J].J Geophys Res,97(B6):8749--8764.
李克.2007.地震学与地震观测[M].北京:地震出版社:172.Li K.2007.Seismology and Earthquake Observation[M].Beijing:Seismological Press:172(in Chinese).
秦满忠,沈旭章,张元生,刘旭宙.2014.利用兰州小孔径地震台阵资料叠加观测走时曲线[J].地震学报,36(1):59--69.Qin M Z,Shen X Z,Zhang Y S,Liu X Z.2014.Observed travel-time curves by stacking records from Lanzhou smallaperture seismic array[J].Acta Seismologica Sinica,36(1):59--69(in Chinese).
唐群署,李丽红.2006.核幔边界D″区的地震学研究进展[J].地学前缘,13(2):213--223.Tang Q S,Li L H.2006.The Earth’s lowermost mantle and its seismological research progress[J].Earth Science Frontiers,13(2):213--223(in Chinese).
唐燕娟.1997.对P波衍射波Pdif震相记录范围的讨论[J].地震地磁观测与研究,18(2):32--36.Tang Y J.1997.A discussion on recorded distance for diffraction wave Pdif of wave P[J].Seismological and Geomagnetic Observation and Research,18(2):32--36(in Chinese).
许健生,隗永刚,张淑珍.2012.Pdif震相在CDSN兰州地震台的记录特征[J].西北地震学报,34(3):239--244.Xu J S,Wei Y G,Zhang S Z.2012.The recording characters of Pdif phase in seismic wave at CDSN Lanzhou seismic station[J].Northwestern Seismological Journal,34(3):239--244(in Chinese).
许健生,隗永刚,张淑珍.2013.Pdif波在中国CDSN台站的运动学特征[J].地震工程学报,35(3):610--617.Xu J S,Wei Y G,Zhang S Z.2013.The kinematic characteristics of Pdif-waves at CDSN stations[J].China EarthquakeEngineering Journal,35(3):610--617(in Chinese).
赵荣国.1987.中国763长周期台网观测到Δ=175.6°的幔-核界面衍射波[J].国际地震动态,(3):14--16.Zhao R G.1987.Waves diffracted at the mantle-core boundary observed by type-763long-period seismograph network ofChina[J].Recent Developments in World Seismology,(3):14--16(in Chinese).
Arthur R,John W.1993.Inference of core-mantle boundary topography from ISC PcP and PKP traveltimes[J].GeophysJ Int,115(3):991--1011.
Astiz L,Earle P,Shearer P.1996.Global stacking of broadband seismograms[J].Seismol Res Lett,67(4):8--18.
Helmberger D V,Wen L,Ding X.1998.Seismic evidence that the source of the Iceland hotspot lies at the core-mantleboundary[J].Nature,396(6708):251--255.
Labrosse S,Hernlund J W,Coltice N.2007.A crystallizing dense magma ocean at the base of the Earth’s mantle[J].Nature,450(7171):866--869.
McNamara A K,Garnero E J,Rost S.2010.Tracking deep mantle reservoirs with ultra-low velocity zones[J].EarthPlanet Sci Lett,299(1/2):1--9.
Mori J,Helmberger D V.1995.Localized boundary layer below the mid-Pacific velocity anomaly identified from a PcPprecursor[J].J Geophys Res,100(B10):20359--20365.
Rial J A.1978.On the focusing of seismic body waves at the epicentre’s antipode[J].Geophys J Int,55(3):737--743.
Rial J A,Cormier V F.1980.Seismic waves at the epicenter’s antipode[J].J Geophys Res,85(B5):2661--2668.
Soldati G,Boschi L,Piersanti A.2006.Global seismic tomography and modern parallel computers[J].Ann Geophys,49(4/5):977--986.
Sun D Y,Helmberger D V,Jackson J M,Clayton R W,Bower D J.2013.Rolling hills on the core-mantle boundary[J].Earth Planet Sci Lett,361:333--342.
Sze E K M,van der Hilst R D.2003.Core mantle boundary topography from short period PcP,PKP,and PKKP data[J].Physics Earth Planet Inter,135(1):27--46.
Wysession M E,Okal E A,Bina C R.1992.The structure of the core-mantle boundary from diffracted waves[J].J Geophys Res,97(B6):8749--8764.
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