几种常用地方震相对天然地震震源深度测定的误差解析分析及数值对比
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摘要
本文从误差解析公式及数值模拟计算两种途径讨论了利用常用地方震相Pg,Sg,Pm P,Pn,s PL测定震源深度的误差问题,结果表明,两种途径获取的误差值相当。对于上地壳的地震而言,当直达波走时误差处于0.1 s的量级时,若要将误差控制在3 km左右,则应选用震中距为30 km以内的台站;当走时误差处于0.2 s的量级时,若要控制同等误差,则应选用震中距为20 km以内的台站;如果地震位于下地壳,震中距可适当放宽,然而当震中距更大或走时误差更大时,震源深度的误差则近乎成倍增长。Pm P,Pn,s PL对上地壳的震源深度测定误差要小于下地壳,同时对误差的控制较好,不会随震中距的增大而快速增大,震中距处于90 km范围以内且走时误差小于0.1 s时的深度误差基本均能控制在3.5 km以内。此外,本文还通过"棋盘格"的方式定量地分析了速度扰动对走时的影响,并以首都圈地区台网布局为基础,分析了加入首波对震源深度测定的改善效果。这两项数值对比结果均表明,在2%的速度扰动下,只要下地壳和莫霍面的速度参数不同时出现过大或过小现象,加入首波后对震源深度的测定误差则基本能控制在3 km以内,且一致性明显地高于单独使用直达波。
In this paper,both analytic and numerical simulation methods were used to discuss the focal depth error resulted from the local seismic phases of Pg,Sg,Pm P,Pn,s PL. The result shows the two above methods produced very close error estimation. For the epicenter in the upper crust,on the condition of travel time error within 0.1 s,in order to ensure the depth error is less than 3 km,we should select these direct wave phases recorded within epicentral distance of 30 km to locate. If the travel time error is up to 0.2 s,we should select these direct wave phases within 20 km to locate on the above same condition. When the hypocenter in the lower crust,the limit of epicentral distance could be broaden a bit. As the epicentral distance or travel time error becomes larger,the error of depth location becomes practically several fold increase.Whereas,the seismic phases of Pm P,Pn,s PL can make a better error constrain when the hypocenter in the upper crust,and without an obvious enlarging effect on error as the epicentral distance increases. For these three mentioned phases,they also can ensure the depth error within 3.5 km when travel time error is set within 0.1 s and epicentral distance is less than 90 km.Furthermore,by the chessboard mode we analyzed the quantitative effect of travel time resulted from the velocity disturbance. And based on the capital seismic network,we analyzed the improvement of depth location after adding head wave phases. The above analyses result show that,within 2% velocity disturbance and without simultaneously too large or too small velocity deviation for the lower crust and Moho interface,adding head wave phases can effectively produce a reliable focal depth within 3 km,and also produce a more homogeneity result than only direct wave phases used.
In this paper,both analytic and numerical simulation methods were used to discuss the focal depth error resulted from the local seismic phases of Pg,Sg,Pm P,Pn,s PL. The result shows the two above methods produced very close error estimation. For the epicenter in the upper crust,on the condition of travel time error within 0.1 s,in order to ensure the depth error is less than 3 km,we should select these direct wave phases recorded within epicentral distance of 30 km to locate. If the travel time error is up to 0.2 s,we should select these direct wave phases within 20 km to locate on the above same condition. When the hypocenter in the lower crust,the limit of epicentral distance could be broaden a bit. As the epicentral distance or travel time error becomes larger,the error of depth location becomes practically several fold increase.Whereas,the seismic phases of Pm P,Pn,s PL can make a better error constrain when the hypocenter in the upper crust,and without an obvious enlarging effect on error as the epicentral distance increases. For these three mentioned phases,they also can ensure the depth error within 3.5 km when travel time error is set within 0.1 s and epicentral distance is less than 90 km.Furthermore,by the chessboard mode we analyzed the quantitative effect of travel time resulted from the velocity disturbance. And based on the capital seismic network,we analyzed the improvement of depth location after adding head wave phases. The above analyses result show that,within 2% velocity disturbance and without simultaneously too large or too small velocity deviation for the lower crust and Moho interface,adding head wave phases can effectively produce a reliable focal depth within 3 km,and also produce a more homogeneity result than only direct wave phases used.
引文
包丰,倪四道,赵建和,谢军,陈伟文,曾祥方.2013.时钟不准情形地震精确定位研究:以2011年1月19日安庆地震序列为例[J].地震学报,35(2):160-172.Bao F,Ni S D,Zhao J H,Xie J,Chen W W,Zeng X F.2013.Accurate earthquake location with instrumental clock error:Acase study for the 19 January 2011 Anqing earthquake sequence[J].Acta Seismologica Sinica,35(2):1 6 0-1 7 2(in Chinese).
崇加军,倪四道,曾祥方.2010.s PL,一个近距离确定震源深度的震相[J].地球物理学报,53(11):2620-2630.Chong J J,Ni S D,Zeng X F.2010.s PL,an effective seismic phase for determining focal depth at near distance[J].Chinese Journal of Geophysics,53(11):2620-2630(in Chinese).
傅淑芳,刘宝诚,李文艺.1980.地震学教程(下册)[M].北京:地震出版社:184-189.Fu S F,Liu B C,Li W Y.1980.A Course in Seismology(Volume II)[M].Beijing:Seismological Press:184-189(in Chinese).
高原,郑斯华,周惠兰.1999.唐山地区快剪切波偏振图像及其变化[J].地球物理学报,42(2):228-232.Gao Y,Zheng S H,Zhou H L.1999.Polarization patterns of fast shear wave in Tangshan region and their variations[J].Chinese Journal of Geophysics,42(2):228-232(in Chinese).
国家地震局地球物理研究所.1978.近震分析[M].北京:地震出版社:128-141.Institute of Geophysics,State Seismological Bureau.1978.Analysis of Local Earthquake[M].Beijing:Seismological Press:128-141(in Chinese).
嘉世旭,齐诚,王夫运,陈棋福,张先康,陈颙.2005.首都圈地壳网格化三维结构[J].地球物理学报,48(6):1316-1324.Jia S X,Qi C,Wang F Y,Chen Q F,Zhang X K,Chen Y.2005.Three-dimensional crustal gridded structure of the capital area[J].Chinese Journal of Geophysics,48(6):1316-1324(in Chinese).
李江海.1991.大陆下地壳研究进展评述[J].地质科技情报,10(1):9-16.Li J H.1991.Review on recent research of the lower continental crust[J].Geological Science and Technology Information,10(1):9-16(in Chinese).
刘双庆,薛艳,蔡宏雷,谢静.2015.利用重测定的震源深度特征探讨2013年吉林前郭5.8级震群发震因素[J].地震研究,38(2):211-220.Liu S Q,Xue Y,Cai H L,Xie J.2015.Discussion on cause factor of Jilin Qianguo MS5.8 earthquake sequence in 2013 using focal depth characteristic of relocation[J].Journal of Seismological Research,38(2):211-220(in Chinese).
刘希强,周彦文,曲均浩,石玉燕,李铂.2009.应用单台垂向记录进行区域地震事件实时检测和直达P波初动自动识别[J].地震学报,31(3):260-271.Liu X Q,Zhou Y W,Qu J H,Shi Y Y,Li B.2009.Real-time detection of regional events and automatic P-phase identification from the vertical component of a single station record[J].Acta Seismologica Sinica,31(3):260-271(in Chinese).
田玥,陈晓非.2005.水平层状介质中的快速两点间射线追踪方法[J].地震学报,27(2):147-154.Tian Y,Chen X F.2005.A rapid and accurate two-point ray tracing method in horizontally layered velocity model[J].Acta Seismologica Sinica,27(2):147-154(in Chinese).
万天丰.2012.中国大陆岩石圈的形成、演化与特征[J].自然杂志,34(4):196-200,218.Wan T F.2012.Formation,evolution and characteristics of China continental lithosphere[J].Chinese Journal of Nature,34(4):196-200,218(in Chinese).
王晓,周小鹏,张新彦,白志明,滕吉文.2015.上地壳纵横波速度结构相关反演成像方法[J].地球物理学报,58(10):3553-3570.Wang X,Zhou X P,Zhang X Y,Bai Z M,Teng J W.2015.Tomographic imaging of velocity structure in upper crust based on correlated inversion of VP and VS[J].Chinese Journal of Geophysics,58(10):3553-3570(in Chinese).
吴微微,杨建思,苏金蓉,杜文康,高瑜,郑钰,田宝峰,刘莎,吴朋.2014.2013年吉林前郭-乾安震源区中强地震矩张量反演与区域孕震环境研究[J].地球物理学报,57(8):2541-2554.Wu W W,Yang J S,Su J R,Du W K,Gao Y,Zheng Y,Tian B F,Liu S,Wu P.2014.Moment inversion of moderate earthquakes and seismogenic environment in Qianguo-Qian’an source region,2013,Jilin Province[J].Chinese Journal of Geophysics,57(8):2541-2554(in Chinese).
叶其孝,沈永欢.2008.实用数学手册[M].第2版.北京:科学出版社:482-483.Ye Q X,Shen Y H.2008.Practical Mathematics Manual[M].2nd ed.Beijing:Science Press:482-483(in Chinese).
翟明国.2010.地球的陆壳是怎样形成的?:神秘而有趣的前寒武纪地质学[J].自然杂志,32(3):125-129,133.Zhai M G.2010.How to originate and evolve for continental crust of the earth-Precambrian geology?:A mysterious and interesting science[J].Chinese Journal of Nature,32(3):125-129,133(in Chinese).
赵仲和.1983.区域地震台网地震定位能力分析[J].地震学报,5(4):467-476.Zhao Z H.1983.Analysis of hypocenter location capability of a regional seismic network[J].Acta Seismologica Sinica,5(4):467-476(in Chinese).
赵铭.2011.天体测量学导论[M].第2版.北京:中国科学技术出版社:302-325.Zhao M.2006.The Introduction to Astrometry[M].2nd ed.Beijing:Science and Technology of China Press:302-325(in Chinese).
中国地震局监测预报司.2017.测震学原理与方法[M].北京:地震出版社:254-281.Department of Earthquake Monitoring and Prediction,China Earthquake Administration.2017.Principle and Method of Seismometry[M].Beijing:Seismological Press:254-281(in Chinese).
朱元清.1989.上海电信传输地震台网监测能力及其定位精度[J].地震地磁观测与研究,10(3):27-32.Zhu Y Q.1989.Analysis to the monitor ability and location error of Shanghai telecommunicating seismic network[J].Seismological and Geomagnetic Observation and Research,10(3):27-32(in Chinese).
朱元清,宋秀青,刘双庆.2017.中国地震测定参考速度结构研究[M].北京:地震出版社:1-5.Zhu Y Q,Song X Q,Liu S Q.2017.Reference Velocity Model for Earthquake Location of Mainland China[M].Beijing:Seismological Press:1-5(in Chinese).
Borman P.2002.New Manual of Seismological Observatory Practice(NMSOP-2)[M].Potsdam:Geo Forchungs Zentrum:55.
Fu C Y.1947.On seismic rays and waves(part one)[J].Bull Seismol Soc Am,37(4):331-346.
Hahm I K,Kim W,Lee J M,Jeon J S.2007.Determination of hypocentral parameters of local earthquakes using weighting factor based on take-off angle[J].Geosci J,11(1):39-49.
Schweitzer J.2001.HYPOSAT:An enhanced routine to locate seismic events[J].Pure Appl Geophys,158(1/2):277-289.
Waldhauser F,Ellsworth W L.2000.A double-difference earthquake location algorithm:Method and application to the northern Hayward fault,California[J].Bull Seismol Soc Am,90(6):1353-1368.
Zhang H J,Thurber C H.2003.Double-difference tomography:The method and its application to the Hayward fault,California[J].Bull Seismol Soc Am,93(5):1875-1889.
崇加军,倪四道,曾祥方.2010.s PL,一个近距离确定震源深度的震相[J].地球物理学报,53(11):2620-2630.Chong J J,Ni S D,Zeng X F.2010.s PL,an effective seismic phase for determining focal depth at near distance[J].Chinese Journal of Geophysics,53(11):2620-2630(in Chinese).
傅淑芳,刘宝诚,李文艺.1980.地震学教程(下册)[M].北京:地震出版社:184-189.Fu S F,Liu B C,Li W Y.1980.A Course in Seismology(Volume II)[M].Beijing:Seismological Press:184-189(in Chinese).
高原,郑斯华,周惠兰.1999.唐山地区快剪切波偏振图像及其变化[J].地球物理学报,42(2):228-232.Gao Y,Zheng S H,Zhou H L.1999.Polarization patterns of fast shear wave in Tangshan region and their variations[J].Chinese Journal of Geophysics,42(2):228-232(in Chinese).
国家地震局地球物理研究所.1978.近震分析[M].北京:地震出版社:128-141.Institute of Geophysics,State Seismological Bureau.1978.Analysis of Local Earthquake[M].Beijing:Seismological Press:128-141(in Chinese).
嘉世旭,齐诚,王夫运,陈棋福,张先康,陈颙.2005.首都圈地壳网格化三维结构[J].地球物理学报,48(6):1316-1324.Jia S X,Qi C,Wang F Y,Chen Q F,Zhang X K,Chen Y.2005.Three-dimensional crustal gridded structure of the capital area[J].Chinese Journal of Geophysics,48(6):1316-1324(in Chinese).
李江海.1991.大陆下地壳研究进展评述[J].地质科技情报,10(1):9-16.Li J H.1991.Review on recent research of the lower continental crust[J].Geological Science and Technology Information,10(1):9-16(in Chinese).
刘双庆,薛艳,蔡宏雷,谢静.2015.利用重测定的震源深度特征探讨2013年吉林前郭5.8级震群发震因素[J].地震研究,38(2):211-220.Liu S Q,Xue Y,Cai H L,Xie J.2015.Discussion on cause factor of Jilin Qianguo MS5.8 earthquake sequence in 2013 using focal depth characteristic of relocation[J].Journal of Seismological Research,38(2):211-220(in Chinese).
刘希强,周彦文,曲均浩,石玉燕,李铂.2009.应用单台垂向记录进行区域地震事件实时检测和直达P波初动自动识别[J].地震学报,31(3):260-271.Liu X Q,Zhou Y W,Qu J H,Shi Y Y,Li B.2009.Real-time detection of regional events and automatic P-phase identification from the vertical component of a single station record[J].Acta Seismologica Sinica,31(3):260-271(in Chinese).
田玥,陈晓非.2005.水平层状介质中的快速两点间射线追踪方法[J].地震学报,27(2):147-154.Tian Y,Chen X F.2005.A rapid and accurate two-point ray tracing method in horizontally layered velocity model[J].Acta Seismologica Sinica,27(2):147-154(in Chinese).
万天丰.2012.中国大陆岩石圈的形成、演化与特征[J].自然杂志,34(4):196-200,218.Wan T F.2012.Formation,evolution and characteristics of China continental lithosphere[J].Chinese Journal of Nature,34(4):196-200,218(in Chinese).
王晓,周小鹏,张新彦,白志明,滕吉文.2015.上地壳纵横波速度结构相关反演成像方法[J].地球物理学报,58(10):3553-3570.Wang X,Zhou X P,Zhang X Y,Bai Z M,Teng J W.2015.Tomographic imaging of velocity structure in upper crust based on correlated inversion of VP and VS[J].Chinese Journal of Geophysics,58(10):3553-3570(in Chinese).
吴微微,杨建思,苏金蓉,杜文康,高瑜,郑钰,田宝峰,刘莎,吴朋.2014.2013年吉林前郭-乾安震源区中强地震矩张量反演与区域孕震环境研究[J].地球物理学报,57(8):2541-2554.Wu W W,Yang J S,Su J R,Du W K,Gao Y,Zheng Y,Tian B F,Liu S,Wu P.2014.Moment inversion of moderate earthquakes and seismogenic environment in Qianguo-Qian’an source region,2013,Jilin Province[J].Chinese Journal of Geophysics,57(8):2541-2554(in Chinese).
叶其孝,沈永欢.2008.实用数学手册[M].第2版.北京:科学出版社:482-483.Ye Q X,Shen Y H.2008.Practical Mathematics Manual[M].2nd ed.Beijing:Science Press:482-483(in Chinese).
翟明国.2010.地球的陆壳是怎样形成的?:神秘而有趣的前寒武纪地质学[J].自然杂志,32(3):125-129,133.Zhai M G.2010.How to originate and evolve for continental crust of the earth-Precambrian geology?:A mysterious and interesting science[J].Chinese Journal of Nature,32(3):125-129,133(in Chinese).
赵仲和.1983.区域地震台网地震定位能力分析[J].地震学报,5(4):467-476.Zhao Z H.1983.Analysis of hypocenter location capability of a regional seismic network[J].Acta Seismologica Sinica,5(4):467-476(in Chinese).
赵铭.2011.天体测量学导论[M].第2版.北京:中国科学技术出版社:302-325.Zhao M.2006.The Introduction to Astrometry[M].2nd ed.Beijing:Science and Technology of China Press:302-325(in Chinese).
中国地震局监测预报司.2017.测震学原理与方法[M].北京:地震出版社:254-281.Department of Earthquake Monitoring and Prediction,China Earthquake Administration.2017.Principle and Method of Seismometry[M].Beijing:Seismological Press:254-281(in Chinese).
朱元清.1989.上海电信传输地震台网监测能力及其定位精度[J].地震地磁观测与研究,10(3):27-32.Zhu Y Q.1989.Analysis to the monitor ability and location error of Shanghai telecommunicating seismic network[J].Seismological and Geomagnetic Observation and Research,10(3):27-32(in Chinese).
朱元清,宋秀青,刘双庆.2017.中国地震测定参考速度结构研究[M].北京:地震出版社:1-5.Zhu Y Q,Song X Q,Liu S Q.2017.Reference Velocity Model for Earthquake Location of Mainland China[M].Beijing:Seismological Press:1-5(in Chinese).
Borman P.2002.New Manual of Seismological Observatory Practice(NMSOP-2)[M].Potsdam:Geo Forchungs Zentrum:55.
Fu C Y.1947.On seismic rays and waves(part one)[J].Bull Seismol Soc Am,37(4):331-346.
Hahm I K,Kim W,Lee J M,Jeon J S.2007.Determination of hypocentral parameters of local earthquakes using weighting factor based on take-off angle[J].Geosci J,11(1):39-49.
Schweitzer J.2001.HYPOSAT:An enhanced routine to locate seismic events[J].Pure Appl Geophys,158(1/2):277-289.
Waldhauser F,Ellsworth W L.2000.A double-difference earthquake location algorithm:Method and application to the northern Hayward fault,California[J].Bull Seismol Soc Am,90(6):1353-1368.
Zhang H J,Thurber C H.2003.Double-difference tomography:The method and its application to the Hayward fault,California[J].Bull Seismol Soc Am,93(5):1875-1889.