汶川地震强余震(M_s≥5.6)的震源机制解及其与发震构造的关系
摘要
在2008年5月12日汶川8.0级地震之后,发生了数十个M>5,数百个M>4以及更多的M>3的余震,固定和流动地震台站对这些地震进行了较完整的监测.通过利用P波到时数据对M>3的余震进行重新定位,发现余震分布有两个明显的趋势,绝大部分的余震都分布在沿龙门山断裂带的北东向上,但在汶川地震的震中附近有一个北西向的余震分布区.利用中国国家数字地震台网和区域地震台网的波形记录,采用"裁剪-粘贴"法,获得了较大余震的震源机制解(Ms≥5.6).从震源机制解来看,尽管多数较强余震显示出逆冲的性质,但在断裂带的北部余震仍有一部分显示出明显的走滑性质.震源机制解显示北川-映秀断裂(BYF)的南部发生的余震主要为逆冲型地震,和主震的滑移状态一致;在BYF断层的北部余震同样以逆冲状态为主,这和主震在该区域的破裂性质有很大差异.在青川-平武断裂附近,震源机制以右旋走滑为主,且震源深度比较深(～18km).由此猜测主震在北部可能发生在北川断裂和青川断裂两个断裂上,而不是只发生在中央断层上.这种复杂的余震机制显示出龙门山断裂带断层系统的复杂性.
引文
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19吕坚,郑勇,倪四道,等.2005年11月26日九江-瑞昌Ms5.7、Ms4.8地震的震源机制解与发震构造研究.地球物理学报,2008,51(1):158—164
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23Waldhauser F,Ellsworth W L.A double-difference earthquake location algorithm:method and application to the northern Hayward fault.Bull Seism Soc Am,2000,90:1353—1368
24宋鸿彪.龙门山造山带地质和地球物理资料的综合解释.成都理工学院学报,1994,21(2):79—88
25赵珠,范军,郑斯华,等.龙门山断裂带地壳速度结构和震源位置的精确修定.地震学报,1997,19(6):615—622
26黄媛,吴建平,张天中,等.汶川8.0级大地震及其余震序列重定位研究.中国科学D辑:地球科学,2008,38(10):1242—1249
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28张培震,徐锡伟,闻学泽,等.2008年汶川8.0级地震法阵断裂的滑动速率、复发周期和构造成因.地球物理学报,2008,51(4):1066—1073
29Engdahl E R,Van der Hilst R D,Buland R.Global teleseismic earthquake relocation with improved travel times and procedures for depth determination.Bull Seismol Soc Amer,1998,88(3):722—743
30Burchfiel B C,Chen Z,Liu Y,et al.Tectonics of the Longmenshan and adjacent regions,central China.Int Geol Rev,1995,37(8):661—735
31汶川地震专家委员会.汶川地震灾区地质构造图.汶川8.0级地震图集.北京:中国地图出版社,2008.6—7
2内蒙古地震局.内蒙古自治区2003年和2004年两次5.9级地震.北京:地震出版社,2005.3—7
3张国民,汪素云,李丽,等.中国大陆地震震源深度及其构造意义.科学通报,2002,47(9):663―668
4McGowan D W.Moment tensor representation of surface wave sources.Geophys J R Astr Soc,1976,44:595—599
5Patton H J.Reference point method for determining the source and path effects of surface waves.J Geophys Res,1980,85:821—848
6Kanamori H,Given J W.Use of long period surface waves for rapid determination of the earthquake source parameters.Phys Earth Planet Inter,1981,27:8—31
7Lay T,Giveva J W,Kanamori H.Long period mechanism of the8November1980Eureka,California,earthquake.Bull Seismol Soc Amer,1982,72:439—456
8Xu L,Rondenay S,van der Hilst R D.Structure of the crust beneath the Southeastern Tibetan Plateau from teleseismic receiver func-tions.Phys Earth Planet Inter,2007,doi:10.1016/j.pepi.2007.09.002
9Dziewonski A M,Chou T A,Woodhouse J H.Determination of earthquake source parameters from waveform data for studies of global and regional seismicity.J Geophys Res,1981,86:2825—2852
10Dreger D S,Helmberger D V.Determination of source parameters at regional distances with three-componet sparse network data.J Geophys Res,1993,98:8107—8125
11Takeo M.An inversion method to analyze the rupture processes of earthquakes using near-field seismogram.Bull Seismol Soc Amer,1987,77:490—513
12Burchfiel,B C,Royden L H,Van der Hilst R D,et al.A geological and geophysical context for the Wenchuan earthquake of12May2008,Sichuan,People’s Republic of China.GSA Today,2008,18(7):4—11,doi:10.1130/GSATG18A.1
13Royden L H,Burchfiel B C,King R W,et al.Surface deformation and lower crsutal flow in eastern Tibetan.Science,1997,276:788—790
14Clark M,Royden L H.Topographic ooze:building the eastern margin of Tibet by lower crustal flow.Geology,2000,28(8):703—706
15郑勇,傅容珊,熊熊.中国大陆及周边地区现代岩石圈演化动力学模拟.地球物理学报,2006,49(2):415—427
16许力生,陈运泰.从全球长周期波形资料反演2001年11月14日昆仑山大地震时空破裂过程.中国科学D辑:地球科学,34(3):256—264
17Yao H,Van der Hilst R D,de Hoop M V.Surface-wave array tomography in SE Tibet from ambient seismic noise and two-station analysis—ⅠPhase velocity maps.Geophys J Int,2006,166:732—744
18Yao H,Beghein C,van der Hilst R D.Surface wave array tomography in SE Tibet from ambient seismic noise and two-station analy-sis—ⅡCrustal and upper-mantle structure.Geophys J Int,2008,doi:10.1111/j.1365-246X.2007.03696.x
19吕坚,郑勇,倪四道,等.2005年11月26日九江-瑞昌Ms5.7、Ms4.8地震的震源机制解与发震构造研究.地球物理学报,2008,51(1):158—164
20Zhu L P,Helmberger D V.Advancement in source estimation techniques using broadband regional seismograms.Bull Seismol Soc Amer,1996,86(5):1634—1641
21Tan Y,Zhu L P,Helmberger D V,et al.Locating and modeling regional earthquakes with two stations.J Geophys Res,2006,111:B01306,doi:1029/2005JB003775.
22Geiger L.Probability method for the determination of earthquake epicenters from the arrival time only(translated from Geiger’s1910German article).Bull St Louis Univ,1912,8(1):56—71
23Waldhauser F,Ellsworth W L.A double-difference earthquake location algorithm:method and application to the northern Hayward fault.Bull Seism Soc Am,2000,90:1353—1368
24宋鸿彪.龙门山造山带地质和地球物理资料的综合解释.成都理工学院学报,1994,21(2):79—88
25赵珠,范军,郑斯华,等.龙门山断裂带地壳速度结构和震源位置的精确修定.地震学报,1997,19(6):615—622
26黄媛,吴建平,张天中,等.汶川8.0级大地震及其余震序列重定位研究.中国科学D辑:地球科学,2008,38(10):1242—1249
27王卫民,赵连锋,李娟,等.四川汶川8.0级地震震源过程.地球物理学报,2008,51(5):1403—1410
28张培震,徐锡伟,闻学泽,等.2008年汶川8.0级地震法阵断裂的滑动速率、复发周期和构造成因.地球物理学报,2008,51(4):1066—1073
29Engdahl E R,Van der Hilst R D,Buland R.Global teleseismic earthquake relocation with improved travel times and procedures for depth determination.Bull Seismol Soc Amer,1998,88(3):722—743
30Burchfiel B C,Chen Z,Liu Y,et al.Tectonics of the Longmenshan and adjacent regions,central China.Int Geol Rev,1995,37(8):661—735
31汶川地震专家委员会.汶川地震灾区地质构造图.汶川8.0级地震图集.北京:中国地图出版社,2008.6—7
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