京津唐地区中小地震重新定位
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摘要
利用华北遥测台网和首都圈数字地震台网112个台站记录到的1993—2004年发生在首都圈地区3983次地震的P波绝对到时资料和相对到时资料,采用双差地震层析成像方法联合反演首都圈地区的地震震源参数,给出了2809次地震的重新定位结果.经地震重新定位后,P波绝对走时均方根残差由初始的1.2s降为0.3s,定位精度有了非常显著的提高.重新定位后的地震震中更集中分布在断层带地区,条带状更为清晰.在唐山地区的唐山—大城断裂带,地震主要集中在断裂带内,两侧的地震比较稀少.从重新定位后的震中分布可以看出,研究区域内的地震活动带呈现更明显的北北东向和北西西向的条带状分布,说明这两组方向的断裂最为活跃.用双差地震层析成像方法得到的唐山地区的地震震源位置,沿北东方向剖面在深度上呈现明显的3个小震群的特点,震源最大深度为25km.唐山地区地震重新定位结果的对比性研究表明,双差层析成像方法得到的震源参数的精度高于常规地震层析成像方法和双差法.
By taking the full advantage of the up-to-date double-difference (DD) seismic tomography method,the 2809 earthquake hypocenters were relocated to enhance their resolution of horizontal and in-depth directions. These earthquakes were all occurred in the Beijing-Tianjin-Tangshan (BTT) region,and the magnitude range of these events was around M1.7-6.2. Absolute arrival time and differential travel time records of 3983 earthquakes during the period 1993-2004 were adopted. These records were elaborately selected from the 112 seismic stations which are parts of both the Northern China Telemetry Seismic Network (NCTSN) and Capital Digital Seismic Network (CDSN). As a result,the root mean square (RMS) residuals of the earthquake hypocenters were greatly reduced from 1.2 s to 0.3 s. The relocated hypocenters of earthquakes showed an even clear configuration along the major faults than that of before relocating. Moreover,some of them were concentrated along with the major faults in a shape of alignment in some particular regions,such as the Tangshan-Dacheng fault zone in Tangshan region. In this region,all the events were mainly located in the fault zones,and only few of them were exceptional. From the horizontal distribution profile of the relocated earthquake hypocenters,the seismicities appeared clearly as two "belt-shape" characteristics both in NNE and WNW directions. It revealed that these two regions are currently seismic active nowadays. From the north-east (NE) cross sectional profile of this region,the relocated hypocenters of earthquakes were clustered as three typical groups,and the maximum focal depth of these earthquakes is 25 km. We also compared our relocation result with those from the standard tomography method and DD relocation method,which used the absolute travel-time catalog data and relative travel-time catalog data,respectively. The comparisons confirmed that our DD tomography could produce much higher resolution hypocenter parameters than that from the standard tomography and DD relocation methods.
By taking the full advantage of the up-to-date double-difference (DD) seismic tomography method,the 2809 earthquake hypocenters were relocated to enhance their resolution of horizontal and in-depth directions. These earthquakes were all occurred in the Beijing-Tianjin-Tangshan (BTT) region,and the magnitude range of these events was around M1.7-6.2. Absolute arrival time and differential travel time records of 3983 earthquakes during the period 1993-2004 were adopted. These records were elaborately selected from the 112 seismic stations which are parts of both the Northern China Telemetry Seismic Network (NCTSN) and Capital Digital Seismic Network (CDSN). As a result,the root mean square (RMS) residuals of the earthquake hypocenters were greatly reduced from 1.2 s to 0.3 s. The relocated hypocenters of earthquakes showed an even clear configuration along the major faults than that of before relocating. Moreover,some of them were concentrated along with the major faults in a shape of alignment in some particular regions,such as the Tangshan-Dacheng fault zone in Tangshan region. In this region,all the events were mainly located in the fault zones,and only few of them were exceptional. From the horizontal distribution profile of the relocated earthquake hypocenters,the seismicities appeared clearly as two "belt-shape" characteristics both in NNE and WNW directions. It revealed that these two regions are currently seismic active nowadays. From the north-east (NE) cross sectional profile of this region,the relocated hypocenters of earthquakes were clustered as three typical groups,and the maximum focal depth of these earthquakes is 25 km. We also compared our relocation result with those from the standard tomography method and DD relocation method,which used the absolute travel-time catalog data and relative travel-time catalog data,respectively. The comparisons confirmed that our DD tomography could produce much higher resolution hypocenter parameters than that from the standard tomography and DD relocation methods.
引文
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邱泽华,马瑾,刘国玺.2005.新发现的唐山地震大断层[J].地震地质,27(4):669-677.
徐常芳.2003.中国大陆壳内与上地幔高导层成因及唐山地震机理研究[J].地学前缘,10(特刊):101-111.
于湘伟,陈运泰,王培德.2003.京津唐地区三维P波速度结构[J].地震学报,25(1):1-14.
于湘伟.2003.近震层析成像理论及其在华北地区的应用[D].北京:中国地震局地球物理研究所:67-84.
于湘伟,陈运泰,张怀.2010.京津唐地区地壳P波三维速度结构与地震活动性分析[J].地球物理学报(待发表)
曾融生,陆涵行,丁志峰.1988.从地震折射和反射剖面结果讨论唐山地震成因[J].地球物理学报,31(4):383-397.
Douglas A,Browers D,Young J B.1997.On the onset of P seismograms[J].Geophys J Int,129(3):681-690.
Pavlis G L.1986.Appraising earthquake hypocenter location errors:a complete practical approach for single-event loca-tions[J].Bull Seism Soc Am,76(6):1699-1717.
Thurber C H.1983.Earthquakelocation andthree-di mensional crustal structureinthe Coyote Lake area,central Califor-nia[J].J Geophys Res,88(B10):8226-8236.
UmJ,Thurber C H.1987.Afast algorithmfor two-point seismic ray tracing[J].Bull Seism Soc Am,77(3):972-986.
Waldhauser F,Ellsworth WL.2000.A double-difference earthquake location algorithm:Method and application to theNorthern Hayward Fault,California[J].Bull Seism Soc Am,90(6):1353-1368.
Waldhauser F,Ellsworth WL.2002.Fault structure and mechanics of the California,fromdouble-difference earthquakelocations[J].J Geophys Res,107(B3):ESE3-1-3-14.
Zhao D,Hasegawa A,Horiuchi S.1992.Tomographic i maging of P and S wave velocity structure beneath northeasternJapan[J].J Geophys Res,97(B13):19909-19928.
Zhang H,Thurber C H.2003.Double-difference tomography:The method andits applicationtothe Haywardfault,Cal-ifornia[J],Bull Seism Soc Am,93(5):1875-1889.
高文学,马瑾.1993.首都圈地震地质环境与地震灾害[M].北京:地震出版社:15-200.
虢顺民.1985.从断块构造运动看唐山地震的发生[G]∥刘恢先主编.唐山大地震震害(一).北京:地震出版社:17-32.
邱泽华,马瑾,刘国玺.2005.新发现的唐山地震大断层[J].地震地质,27(4):669-677.
徐常芳.2003.中国大陆壳内与上地幔高导层成因及唐山地震机理研究[J].地学前缘,10(特刊):101-111.
于湘伟,陈运泰,王培德.2003.京津唐地区三维P波速度结构[J].地震学报,25(1):1-14.
于湘伟.2003.近震层析成像理论及其在华北地区的应用[D].北京:中国地震局地球物理研究所:67-84.
于湘伟,陈运泰,张怀.2010.京津唐地区地壳P波三维速度结构与地震活动性分析[J].地球物理学报(待发表)
曾融生,陆涵行,丁志峰.1988.从地震折射和反射剖面结果讨论唐山地震成因[J].地球物理学报,31(4):383-397.
Douglas A,Browers D,Young J B.1997.On the onset of P seismograms[J].Geophys J Int,129(3):681-690.
Pavlis G L.1986.Appraising earthquake hypocenter location errors:a complete practical approach for single-event loca-tions[J].Bull Seism Soc Am,76(6):1699-1717.
Thurber C H.1983.Earthquakelocation andthree-di mensional crustal structureinthe Coyote Lake area,central Califor-nia[J].J Geophys Res,88(B10):8226-8236.
UmJ,Thurber C H.1987.Afast algorithmfor two-point seismic ray tracing[J].Bull Seism Soc Am,77(3):972-986.
Waldhauser F,Ellsworth WL.2000.A double-difference earthquake location algorithm:Method and application to theNorthern Hayward Fault,California[J].Bull Seism Soc Am,90(6):1353-1368.
Waldhauser F,Ellsworth WL.2002.Fault structure and mechanics of the California,fromdouble-difference earthquakelocations[J].J Geophys Res,107(B3):ESE3-1-3-14.
Zhao D,Hasegawa A,Horiuchi S.1992.Tomographic i maging of P and S wave velocity structure beneath northeasternJapan[J].J Geophys Res,97(B13):19909-19928.
Zhang H,Thurber C H.2003.Double-difference tomography:The method andits applicationtothe Haywardfault,Cal-ifornia[J],Bull Seism Soc Am,93(5):1875-1889.
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