以震源机制类型划分汶川、玉树地震构造块体归属
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摘要
2001年11月14日昆仑山口7.8级地震、2008年3月21日于田7.1级和5月12日的汶川7.9级地震,全部发生在青藏高原中部,构成新的地震活动组.昆仑山口和汶川地震分别位于巴颜喀拉活动地块的北部和东部边界,于田地震发生在该地块的西端.GPS的观测资料分析表明该块体整体向东运动.发生在块体不同部位的昆仑山口、于田和汶川3次大地震震源机制类型体现了巴颜喀拉块体活动力学的一致性.汶川主震和强余震发生之前,出现于田序列余震的强度和频度显著增高,进一步证实同一活动地块地震之间的内在联系.2010年4月14日玉树发生6.9级地震,连同1996年11月19日的喀喇昆仑山口6.9级地震和1997年11月18日玛尼7.5级地震,都发生在巴颜喀拉活动地块的南部边界上,震源机制表现为一致的左旋走向滑动,证实它们属于羌塘块体向东运动的结果.事实表明活动块体具有整体运动的性质,而整体运动也是两组各自3次大地震成组活动的原因.
The November 14,2001 M_w7.8 Kunlun Mountain Pass earthquake,the March 21, 2008 M_w7.1 Yutian earthquake and the May 12,2008 M_w7.9 Wenchuan earthquake all occurred in the middle of Tibet Plateau and formed a new seismicity group.The epicenter of Kunlun Mountain Pass Earthquake and Wenchuan Earthquake was located at the northern and eastern boundary of Bayankala Block respectively and the Yutian earthquake on the western end of it. GPS observational data indicate that this block moves to east.The rupture characteristics of the three large earthquakes in different parts of the block suggest the mechanical consistency of the Bayankala block motion.The intensity and frequency of Yutian aftershocks significantly increased before the main shock and the stronger aftershock of Wenchuan earthquake,which proves that there is an internal relation between the three large earthquakes.The April 14,2010 M_w6.9 Yushu earthquake,the November 19,1996 M_w6.9 Karakorum mountain earthquake and the November 18,1997 M_w7.5 Mani earthquake all occurred on the southern boundary of Bayankala block,and their focal mechanisms are consistently left-lateral strike slip,which were caused by the eastward motion of Qiangtang block and formed a new strong earthquake group.The results show that the block has the character of rigid body motion which is the common origin of the two large earthquake groups.
The November 14,2001 M_w7.8 Kunlun Mountain Pass earthquake,the March 21, 2008 M_w7.1 Yutian earthquake and the May 12,2008 M_w7.9 Wenchuan earthquake all occurred in the middle of Tibet Plateau and formed a new seismicity group.The epicenter of Kunlun Mountain Pass Earthquake and Wenchuan Earthquake was located at the northern and eastern boundary of Bayankala Block respectively and the Yutian earthquake on the western end of it. GPS observational data indicate that this block moves to east.The rupture characteristics of the three large earthquakes in different parts of the block suggest the mechanical consistency of the Bayankala block motion.The intensity and frequency of Yutian aftershocks significantly increased before the main shock and the stronger aftershock of Wenchuan earthquake,which proves that there is an internal relation between the three large earthquakes.The April 14,2010 M_w6.9 Yushu earthquake,the November 19,1996 M_w6.9 Karakorum mountain earthquake and the November 18,1997 M_w7.5 Mani earthquake all occurred on the southern boundary of Bayankala block,and their focal mechanisms are consistently left-lateral strike slip,which were caused by the eastward motion of Qiangtang block and formed a new strong earthquake group.The results show that the block has the character of rigid body motion which is the common origin of the two large earthquake groups.
引文
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[2] 李钦祖,于利民,王吉易等.中国大陆强地震的成组活动和概率预报.中国科学(B辑),1993,23(5) :519～526 Li Q Z,Yu L M,Wang J Y,et al.Grouping occurrences and probability prediction of the strong earthquakes in Chinese mainland.Science in China (Series B) (in Chinese),1993,23(5) :519～526
[3] 张培震,邓起东,张国民等.中国大陆的强震活动与活动地块.中国科学(D辑),2003,33(增刊):12～20 Zhang P Z,Deng Q D,Zhang G M,et al.Strong earthquake activity and active blocks in China mainland.Science in China (SeriesD) (in Chinese),2003,33(Suppl.):12～20
[4] Xu X W,Yu G H,Klinger Y,et al.Reevaluation of surface rupture parameters and faulting segmentation of the 2001 Kunlunshan earthquake (M_w7． 8) ,northerm Tibetan Plateau,China.J.Geophys.Res.,2006,111,B05316,doi:10． 1029/2004JB003488
[5] 李志海,马宏生,曲延军.2008年3月21日新疆于田7． 3级地震发震构造与震前地震活动特征研究.中国地震,2009,25(2) :199～205 Li Z H,Ma H S,Qu Y J.Study on seismogenic structure and seismic activity characteristics before the Yutian M7． 3 earthquake on March 21,2008,Xinjiang.Earthquake Research in China (in Chinese),2009,25(2) :199～205
[6] 徐锡伟,闻学泽,叶建青等.汶川M_s8． 0地震地表破裂带及其发震构造.地震地质,2008,30(3) :597～629 Xu X W,Wen X Z,Ye J Q,et al.The M_s8． 0 Wenchuan earthquake surface ruptures and its seismogenic structure.Seismology and Geology (in Chinese),2008,30(3) :597～ 629
[7] 张培震,徐锡伟,闻学泽等.2008年汶川8． 0级地震发震断裂的滑动速率、复发周期和构造成因.地球物理学报,2008,51(4) :1066～1073 Zhang P Z,Xu X W,Wen X Z,et al.Slip rates and recurrence intervals of the Longmen Shan active fault zone,and tectonic implications for the mechanism of the May 12 Wenchuan earthquake,2008,Sichuan,China.Chinese J.Geophys.(in Chinese),2008,51(4) :1066～1073
[8] 万永革,沈正康,盛书中等.2008年新疆于田7． 3级地震对周围断层的影响及其正断层机制的区域构造解释.地球物理学报,2010,53(2) :280～289 Wan Y G,Shen Z K,Sheng S Z,et al.The mechanical effects of the 2008 M_s7． 3 Yutian,Xinjiang earthquake on the neighboring faults and its tectonic origin of normal faulting mechanism.Chinese J.Geophys.(in Chinese),2010,53(2) :280～289
[9] 王琼,聂晓红,温和平.2008年新疆于田M_s7． 3地震前区域地震活动和应力状态特征初步研究.地震学报,2009,31(3) :235～244 Wang Q,Nie X H,Wen H P.Preliminary research on the characteristics of regional seismic activity and stress state before the 2008 M_s7． 3 earthquake in Yutian,Xinjiang of China.Acta Seismologica Sinica (in Chinese),2009,31(3) :235～244
[10] Selva J,W Marzocchi.Focal parameters,depth estimation and plane selection of the worldwide shallow seismicity with M_s≥7． 0 for the period 1900～1976． Geochem.Geophys. Geosyst.,2004,5,Q05005,doi:10． 1029/2003GC000669．
[11] http://www.globalcmt.org/CMTsearch.html[2010-04-20]
[12] 王伟,王琪.GPS观测约束下的中国大陆活动块体地块运动学模型.大地测量与地球动力学,2008,28(4) :74～82 Wang W,Wang Q.Kinematical model of crustal blocks of China continent revealed by GPS measurements.Journal of Geodesy and Geodynamics (in Chinese).2008,28(4) :74～82
[13] Tapponnier P,Xu Z Q,Roger F,et al.Oblique stepwise rise and growth of the Tibet Plateau.Science,2001,294:1671～1677
[14] Royden L H,Burchfiel B C,King R W,et al.Surface deformation and lower crustal flow in eastern Tibet.Science,1997,276:788～790
[15] Shen F,Leigh H R,Burchtiel B C.Large-scale crustal deformation of the Tibetan Plateau.J.Geophys.Res.,2001,106,6793～6816,doi:10． 1029/2000JB900389
[16] Thatcher W.Microplate model for the present-day deformation of Tibet.J.Geophys.Res.,2007,112,B01401,doi:10． 1029/2005JB004244
[17] Meade B J.Present-day kinematics at the India-Asia collision zone.Geology,2007,35:81～84
[18] Zhang P Z,Shen Z K,Wang M,et al.Continuous deformation of the Tibetan Plateau from global positioning system data.Geology,2004,32:809～812
[19] Wang Q,Zhang P Z,Freymueller J T,et al.Present-day crustal deformation in China constrained by Global Positioning System measurements.Science,2001,294(5542) :574～577
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