天祝—古浪地区双差地震层析成像与古浪地震构造探讨
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摘要
利用观测走时、走时残差和波形互相关方法获得走时残差,采用双差地震层析方法对1996年6月1日天祝5.2级地震后布设的微震台网资料进行处理,获得了台网下方上地壳三维速度结构的基本特征和地震绝对位置的空间展布特征,并由此勾画出区域活动断裂在深部的延伸情况.地震层析结果表明,研究区上地壳速度结构在纵向和横向上具有明显的非均匀性,地表附近呈现出从南到北高低速相间的速度结构特征.地震主要发生在P波高速度或高低速过渡区域,代表坚硬岩层的壳内高速体为强震的孕育和发生提供了重要基础.祁连山逆冲断裂1927年5月23日古浪8.0级地震的发生与祁连山逆冲断裂下方高速度区有着必然的联系.
Double-difference seismic tomography method,which makes use of both absolute and relative arrival times of seismic phases,is adopted to image the velocity structure beneath seismic stations and relocate aftershocks of the 1 Jun 1996 Tianzhu MW5.2 earthquake recorded by a surveillance network of 6 digital seismic stations.Depth extent of active faults is deduced from the velocity structure and relocated earthquakes.The imaged velocity distribution shows that in upper crust there are obvious heterogeneity both horizontally and vertically.It reveals as alternative high and low velocity zones near surface along a N--S AA' profile.The earthquakes took place mainly in high velocity zones and high to low velocity transition zones.High velocity body represented by hard rock is crucial for preparation and occurrence of large events.The occurrence of 1927 Gulang M8.0 earthquake was inevitably related to a high velocity zone under Qilianshan thrust.
Double-difference seismic tomography method,which makes use of both absolute and relative arrival times of seismic phases,is adopted to image the velocity structure beneath seismic stations and relocate aftershocks of the 1 Jun 1996 Tianzhu MW5.2 earthquake recorded by a surveillance network of 6 digital seismic stations.Depth extent of active faults is deduced from the velocity structure and relocated earthquakes.The imaged velocity distribution shows that in upper crust there are obvious heterogeneity both horizontally and vertically.It reveals as alternative high and low velocity zones near surface along a N--S AA' profile.The earthquakes took place mainly in high velocity zones and high to low velocity transition zones.High velocity body represented by hard rock is crucial for preparation and occurrence of large events.The occurrence of 1927 Gulang M8.0 earthquake was inevitably related to a high velocity zone under Qilianshan thrust.
引文
丁志峰,曾融生.1994.用近震资料反演京津塘地区的地壳三维速度结构[J].华北地震科学,12(2):14--20.
何文贵,刘百篪,吕太乙,袁道阳,刘小凤.1996.天祝盆地边缘断层的全新世活动及盆地的演化与形成[J].西北地震学报,18(1):61--66.
雷建设,赵大鹏,苏金蓉,张光伟,李凤.2009.龙门山断裂带地壳精细结构与汶川地震发震机理[J].地球物理学报,52(2):339--345.
李强,王椿镛,刘瑞丰,王溪莉,陈光英,陈光,李桂银.1999.应用层析成像技术研究华北地壳速度结构[J].地震地磁观测与研究,20(5):88--97.
刘福田,曲克信,吴华,李强,刘建华,胡戈.1989.中国大陆及其邻近地区的地震层析成象[J].地球物理学报,32(3):281--291.
刘瑞丰,陈培善,李强.1993.云南及其邻近地区三维速度图象[J].地震学报,15(1):61--67.
荣代潞,李亚荣,金铭,蒋续媛.2000.利用单台数字地震记录反演天祝—古浪5.4级地震矩张量[J].高原地震,12(2):32--36.
王椿镛,林中洋,陈学波.1995.青海门源至福建宁德地学断面综合地球物理研究[J].地球物理学报,38(5):590--598.
吴建平,黄嫒,张天中,明跃红,房立华.2009.汶川MS8.0地震余震分布及周边区域P波三维速度结构研究[J].地球物理学报,52(2):320--328.
于湘伟,陈运泰,张怀.2010.京津唐地区中小地震重新定位[J].地震学报,32(3):257--269.
Gaudemer Y,Tapponnier P,Meyer B,Peltzer G,Shunmin G,Chen Z T,Dai H G,Cifuentes I.1995.Partitioning ofcrustal slip betweenlinked active faultsinthe eastern Qilianshan,and evidence for a major seismic gap,the“Tianzhugap”,on the western Haiyuan fault,Gansu(China)[J].Geophys J Int,120(3):599--645.
Lee W H K,Stewart S W.1981.Principles and applications of microearthquake networks[M]∥Adv Geophys Suppl2.Academic Press,Inc:293.
Liu ZJ,Klinger Y,Xu X,Lasserre C,Chen G,Chen W,Tapponnier P,Zhang B.2007.Millenniumrecurrence of largeearthquakes on the Haiyuanfault near Songshan,Gansu province,China[J].Bull SeismSoc Amer,97(1):14--34,doi:10.1785/0120050118.
Nadeau R,Antolik M,Johnson P A,Foxall W,McEvilly T V.1994.Seismological studies at Parkfield.Ш:Microearth-quake clusters in the study of fault-zone dynamics[J].Bull Seismol Soc Amer,84(1):247--263.
Nicholson C,Lees J M.1992.Travel-time tomography in the northern Coachella Valley using aftershocks of the1986ML5.9north Pal mSprings earthquake[J].Geophys Res Lett,19(1):1--4.
Paige C C,Saunders M A.1982.LSQR:An algorithmfor sparse linear equations and least squares[J].ACM TransMath Soft w,8(1):43--71.
Poupinet G,Ellsworth V L,Frechet J.1984.Monitoring velocity variations in the crust using earthquake doublets:Anapplication to the Calaveras Fault,California[J].J Geophys Res,89(7):5719--5732.
Rubin A M,Gillard D,Got J L.1999.Streaks of microearthquakes along creeping faults[J].Nature,400:635--641.
Schaff D P,Bokel mann G H R,Ellsworth WL,Zanzerkia E,Waldhauser F,Beroza G C.2004.Optimizing correlationtechniques for improved earthquake location[J].Bull Seism Soc Amer,94(2):705--721.
Shearer P M.1997.Improvinglocal earthquake locations using the L1normand waveformcross correlation:Applicationto the Whittier Narrows,California,aftershock sequence[J].J Geophys Res,102(B4):8269--8283.
UmJ,Thurber C H.1987.Afast algorithmfor two-point seismic ray tracing[J].Bull Seism Soc Amer,77(3):972--986.
Waldhauser F.2001.HypoDD:A computer programto compute double-difference hypocenter locations[R]∥US GeolSurv Open File Rept,01-113:25.
Waldhauser F,Ellsworth WL.2000.Adouble-difference earthquake location algorithm:Method and application to thenorthern Hayward Fault,California[J].Bull Seism Soc Amer,90(6):1353--1368.
Waldhauser F,Ellsworth W L.2002.Fault structure and mechanics of the Hayward Fault,California,from double-difference earthquake locations[J].J Geophys Res,107(B3):1--15.
Waldhauser F,Ellsworth WL,Cole A.1999.Slip-parallel seismic lineations on the northern Hayward Fault,California[J].Geophy Re Lett,26(23):3525--3528.
Zhang HJ,Thurber C H.2003.Double-difference tomography:The method andits application to the Hayward Fault,California[J].Bull Seism Soc Amer,93(5):1875--1889.
Zhao D,Hasegawa A,Horiuchi S.1992.Tomographic imaging of P and S wave velocity structure beneath northeasternJapan[J].J Geophys Res,97(B13):19909--19928.
何文贵,刘百篪,吕太乙,袁道阳,刘小凤.1996.天祝盆地边缘断层的全新世活动及盆地的演化与形成[J].西北地震学报,18(1):61--66.
雷建设,赵大鹏,苏金蓉,张光伟,李凤.2009.龙门山断裂带地壳精细结构与汶川地震发震机理[J].地球物理学报,52(2):339--345.
李强,王椿镛,刘瑞丰,王溪莉,陈光英,陈光,李桂银.1999.应用层析成像技术研究华北地壳速度结构[J].地震地磁观测与研究,20(5):88--97.
刘福田,曲克信,吴华,李强,刘建华,胡戈.1989.中国大陆及其邻近地区的地震层析成象[J].地球物理学报,32(3):281--291.
刘瑞丰,陈培善,李强.1993.云南及其邻近地区三维速度图象[J].地震学报,15(1):61--67.
荣代潞,李亚荣,金铭,蒋续媛.2000.利用单台数字地震记录反演天祝—古浪5.4级地震矩张量[J].高原地震,12(2):32--36.
王椿镛,林中洋,陈学波.1995.青海门源至福建宁德地学断面综合地球物理研究[J].地球物理学报,38(5):590--598.
吴建平,黄嫒,张天中,明跃红,房立华.2009.汶川MS8.0地震余震分布及周边区域P波三维速度结构研究[J].地球物理学报,52(2):320--328.
于湘伟,陈运泰,张怀.2010.京津唐地区中小地震重新定位[J].地震学报,32(3):257--269.
Gaudemer Y,Tapponnier P,Meyer B,Peltzer G,Shunmin G,Chen Z T,Dai H G,Cifuentes I.1995.Partitioning ofcrustal slip betweenlinked active faultsinthe eastern Qilianshan,and evidence for a major seismic gap,the“Tianzhugap”,on the western Haiyuan fault,Gansu(China)[J].Geophys J Int,120(3):599--645.
Lee W H K,Stewart S W.1981.Principles and applications of microearthquake networks[M]∥Adv Geophys Suppl2.Academic Press,Inc:293.
Liu ZJ,Klinger Y,Xu X,Lasserre C,Chen G,Chen W,Tapponnier P,Zhang B.2007.Millenniumrecurrence of largeearthquakes on the Haiyuanfault near Songshan,Gansu province,China[J].Bull SeismSoc Amer,97(1):14--34,doi:10.1785/0120050118.
Nadeau R,Antolik M,Johnson P A,Foxall W,McEvilly T V.1994.Seismological studies at Parkfield.Ш:Microearth-quake clusters in the study of fault-zone dynamics[J].Bull Seismol Soc Amer,84(1):247--263.
Nicholson C,Lees J M.1992.Travel-time tomography in the northern Coachella Valley using aftershocks of the1986ML5.9north Pal mSprings earthquake[J].Geophys Res Lett,19(1):1--4.
Paige C C,Saunders M A.1982.LSQR:An algorithmfor sparse linear equations and least squares[J].ACM TransMath Soft w,8(1):43--71.
Poupinet G,Ellsworth V L,Frechet J.1984.Monitoring velocity variations in the crust using earthquake doublets:Anapplication to the Calaveras Fault,California[J].J Geophys Res,89(7):5719--5732.
Rubin A M,Gillard D,Got J L.1999.Streaks of microearthquakes along creeping faults[J].Nature,400:635--641.
Schaff D P,Bokel mann G H R,Ellsworth WL,Zanzerkia E,Waldhauser F,Beroza G C.2004.Optimizing correlationtechniques for improved earthquake location[J].Bull Seism Soc Amer,94(2):705--721.
Shearer P M.1997.Improvinglocal earthquake locations using the L1normand waveformcross correlation:Applicationto the Whittier Narrows,California,aftershock sequence[J].J Geophys Res,102(B4):8269--8283.
UmJ,Thurber C H.1987.Afast algorithmfor two-point seismic ray tracing[J].Bull Seism Soc Amer,77(3):972--986.
Waldhauser F.2001.HypoDD:A computer programto compute double-difference hypocenter locations[R]∥US GeolSurv Open File Rept,01-113:25.
Waldhauser F,Ellsworth WL.2000.Adouble-difference earthquake location algorithm:Method and application to thenorthern Hayward Fault,California[J].Bull Seism Soc Amer,90(6):1353--1368.
Waldhauser F,Ellsworth W L.2002.Fault structure and mechanics of the Hayward Fault,California,from double-difference earthquake locations[J].J Geophys Res,107(B3):1--15.
Waldhauser F,Ellsworth WL,Cole A.1999.Slip-parallel seismic lineations on the northern Hayward Fault,California[J].Geophy Re Lett,26(23):3525--3528.
Zhang HJ,Thurber C H.2003.Double-difference tomography:The method andits application to the Hayward Fault,California[J].Bull Seism Soc Amer,93(5):1875--1889.
Zhao D,Hasegawa A,Horiuchi S.1992.Tomographic imaging of P and S wave velocity structure beneath northeasternJapan[J].J Geophys Res,97(B13):19909--19928.