2008年青海大柴旦6.3级地震及发震背景研究
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摘要
2008年11月10日青海省大柴旦地区发生6.3级地震,打破了青海省境内55个月的6级地震平静,该次地震可能是对2008年5月12日汶川8.0级地震在青藏块体内部应力调整的响应.通过该次地震及其发震断裂周缘地震震源机制解的分析认为,本次地震发震断裂活动性主要以逆冲为主并兼有走滑特性.对本次地震的发震断裂大柴旦—宗务隆山断裂带开挖探槽,探槽剖面揭露该断裂带在晚更新世—全新世早期有过明显活动;断裂带周缘历史地震的分布特征表明断裂带新的活动明显向南迁移;这与野外调查结果断层活动不断向山前迁移相一致.根据对青藏块体内部地震活动性分析认为,青藏高原内部中强震活动有顺时针螺旋迁移的特征,这一活动特征与GPS观测的青藏块体内部应力顺时针调整相一致,这一特征可能代表了青藏块体内部地震活动的一种新规律.基于对这种规律的认识和祁连地震带的大震构造孕育条件,祁连地震带东南部地区应倍受关注.
A M_s6.3 earthquake occurred in the Dacaidan region,Qinghai province on 10 November 2008,breaking the 55 months-long quiet of the province.It was probably the response to stress adjustment within the Qinghai-Xizang block cause by the Wenchuan M_s8.0 event on 12 May 2008.The analysis of focal mechanisms of this shock and other events surrounding its seismogenic fault suggests that this fault is dominated by thrusting with a strike-ship component.To investigate this fault,we have dug some trenches on the Dacaidan-Zongwulong shan fault zone.The trench profile reveals that this fault was very active during late Pleistocene-early Holocene time.Distribution of historical earthquakes around the fault indicated that the new activity of the fault shifts toward south,consistent with the continued migration of faulting to the range front observed in field investigations.The study on seismicity in the Qinghai-Xizang block suggests that the moderate and large earthquake in the block tend to migrate in a clockwise rotation,which coincides with the clockwise rotation of GPS velocity vectors.It is likely a new rule of earthquake in the block.Based on this insight and tectonic conditions for major earthquakes of the Qilianshan seismic zone,we suggest that much attention should be focused on the southeast of the Qilian shan zone.
A M_s6.3 earthquake occurred in the Dacaidan region,Qinghai province on 10 November 2008,breaking the 55 months-long quiet of the province.It was probably the response to stress adjustment within the Qinghai-Xizang block cause by the Wenchuan M_s8.0 event on 12 May 2008.The analysis of focal mechanisms of this shock and other events surrounding its seismogenic fault suggests that this fault is dominated by thrusting with a strike-ship component.To investigate this fault,we have dug some trenches on the Dacaidan-Zongwulong shan fault zone.The trench profile reveals that this fault was very active during late Pleistocene-early Holocene time.Distribution of historical earthquakes around the fault indicated that the new activity of the fault shifts toward south,consistent with the continued migration of faulting to the range front observed in field investigations.The study on seismicity in the Qinghai-Xizang block suggests that the moderate and large earthquake in the block tend to migrate in a clockwise rotation,which coincides with the clockwise rotation of GPS velocity vectors.It is likely a new rule of earthquake in the block.Based on this insight and tectonic conditions for major earthquakes of the Qilianshan seismic zone,we suggest that much attention should be focused on the southeast of the Qilian shan zone.
引文
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[10] 张希,张晓亮,王双绪,等.青藏块体东北缘近期地壳水平运动与应变积累[J].大地测量与地球动力学,2008,28(4) :12～ 16． Zhang X, Zhang X L, Wang S X, et al. Recent horizontal crustal movement and strain accumulation in northeastern margin of Qinghai-tibet block[J]. Journal of Geodesy and Geodynamics, 2008,28(4) :12～16．
[11] 屠泓为,李智敏,罗国富,等.太阳黑子活动周期对中国大陆西部不同震级段地震的影响探讨与分析[J].地球物理学进展,2009,24(3) :879～885． Tu H W, Li Z M, Luo G F, et al. Discuss and analyze of sunspot activity periods impact on the vary segment magnitude earthquake of west China [ J ]. Progress in Geophysics, 2009,24 (3) : 879 ～ 885．
[12] 屠泓为,张小香,万秀红,等.中国大陆西部未来强震危险性预测研究[J].高原地震,2008,20(2) :4～10． Tu H W, Zhang X X, Wan X H,etal. Discussion on the risk of strong earthquakes in the future in west of Chinese mainland [J ]. Plateau Earthquake Research, 2008,20 (2) : 4 ～10．
[13] 常利军,王椿镛,丁志峰,等.青藏高原东北缘上地幔各向异性研究[J].地球物理学报,2008,51(2) :431～438． Chang L J,Wang C Y,Ding Z F, et al. Seismic anisotropy of upper mantle in the northeastern margin of the Tibetan Plateau[J]. Chinese J. Geophys. (in Chinese), 2008,51(2) :431～438．
[14] 徐纪人,赵志新,石川有三.中国大陆地壳应力场与构造运动区域特征研究[J].地球物理学报,2008,51(3) :770～781． Xu J R, Zhao Z X, Ishikawa Yuzo. Regional characteristics of crustal stress field and tectonic motions in and around Chinese mainland[J]. Chinese J. Geophys. (in Chinese),2008, 51(3) :770～781．
[15] 陈祖安,林邦慧,白武明.1997年玛尼地震对青藏川滇地区构造块体系统稳定性影响的三维DDA+FEM方法数值模拟[J].地球物理学报,2008,51(5) :1422～1430． Chen Z A, Lin B H, Bai W M. 3-D numerical simulation on influence of 1997 Mani earthquake occurrence to stability of tectonic blocks system in Qingzang and Chuandian zone using DDA+FEM method[J]. Chinese J. Geophys. (in Chinese), 2008, 51(5) :1422～1430．
[16] 周仕勇.川西及邻近地区地震活动性模拟和断层间相互作用研究[J].地球物理学报,2008,51(1) :165～174． Zhou S Y. Seismicity simulation in Western Sichuan of China based on the fault interactions and its implication on the estimation of the regional earthquake risk[J]. Chinese J.Geophys. (in Chinese), 2008, 50(1) : 165～174．
[17] 高孟潭,周本刚,潘华.“5·12”汶川特大地震灾害特点及其防灾启示[J].震灾防御技术,2008,3(3) :209～215． Gao M T, Zhou B G, Pan H. Damage characteristics and enlightenment of disaster prevention of " 5． 12" Wenchuan earthquake [ J ]. Technology for Earthquake Disaster Prevention, 2008,3 (3) : 209 ～ 215．
[2] 蒋峰云,王双绪,张希,等.用二维有限元研究青藏块体东北缘地壳的水平运动[J].大地测量与地球动力学,2007,27(4) :21～30． Jiang F Y, Wang S X, Zhang X, et al. On horizontal crust movement in northeeastern margin of Qinghai-tibet block with 2D fem [J]. Journal of Geodesy and Geodynamics, 2007,27 (4) :21 ～30．
[3] 刘小龙,袁道阳.青海德令哈巴音郭勒河断裂带的新活动特征[J].西北地震学报,2004,26(4) :303～308． Liu X L, Yuan D Y. Study on the new active features of bayinguole river active fault, Delingha, Qinghai Province [ J ]. Northwestern Seismological Journal, 2004,26 (4) : 303 ～ 308．
[4] 田勤俭,丁国瑜,申旭辉.青藏高原东北隅强震构造模型[J].地震,2002,22(1) ,9～16． Tian Q J,Ding G Y,Shen X H. Seismic tectonic model of the northeastern corner of the Tibet Plateau[J], Earthquake, 2002,22(1) ,9～16．
[5] 田勤俭,李智敏,张军龙,等.西宁市活断层地震构造模型初步研究[J],地震地质,2007,29(2) :311～319． Tian Q J, Li Z M, Zhang J L, et al. A preliminary study on seismotectonic model for the active faults in Xining urban area[J]. Seismology and Geology, 2007,29 (2) : 311 ～319．
[6] 姚宜斌.利用高精度复测GPS网进行中国大陆区域地壳运动特征分析[J].地球物理学进展,2008,23(4) :1030～1037． Yao Y B. Analysis of crustal movement characteristics in the China mainland by high precision repeated measurements of GPSnetwork [J]. Progress in Geophysics, 2008,23 (4) :1030～1037．
[7] 叶建青,沈军,汪一鹏,等.柴达木盆地北缘的活动构造[J].活动断裂研究,1996,5:172～180． Ye J Q,Shen J ,Wang Y P,et al. The Northern marginal active tectonics of Qaidam basin[J]. Resaerch on Active Fault, 1996, 5:172～180．
[8] 袁道阳,张培震,刘百篪,等.青藏高原东北缘晚第四纪活动构造的几何图像与构造转换[J].地质学报,2004,78(2) :270～278． Yuan D Y,Zhang P Z,Liu B C,et al. Geometrical imagery and tectonic transformation of Late Quaternary active tectonics in Northeastren margin of Qinghai-Xizang Plateau [J ]. Acta Geologica Sinica, 2004,78(2) :270～278．
[9] 袁道阳,张培震,刘小龙,等.青海鄂拉山断裂晚第四纪构造活动及其所反映的青藏高原东北缘的变形机制[J].地学前缘,2004,11(4) :393～403． Yuan D Y,Zhang P Z,Liu X L,et al. The tectonic activity and deformation features during the Latte Quaternary of Elashan Mountain active fault zone in Qinhai Province and its implication for the deformation of the northeastern margins of the Qinghai_Tibet Plateau[J]. Earth Science Frontiers, 2004, 11(4) :393～403．
[10] 张希,张晓亮,王双绪,等.青藏块体东北缘近期地壳水平运动与应变积累[J].大地测量与地球动力学,2008,28(4) :12～ 16． Zhang X, Zhang X L, Wang S X, et al. Recent horizontal crustal movement and strain accumulation in northeastern margin of Qinghai-tibet block[J]. Journal of Geodesy and Geodynamics, 2008,28(4) :12～16．
[11] 屠泓为,李智敏,罗国富,等.太阳黑子活动周期对中国大陆西部不同震级段地震的影响探讨与分析[J].地球物理学进展,2009,24(3) :879～885． Tu H W, Li Z M, Luo G F, et al. Discuss and analyze of sunspot activity periods impact on the vary segment magnitude earthquake of west China [ J ]. Progress in Geophysics, 2009,24 (3) : 879 ～ 885．
[12] 屠泓为,张小香,万秀红,等.中国大陆西部未来强震危险性预测研究[J].高原地震,2008,20(2) :4～10． Tu H W, Zhang X X, Wan X H,etal. Discussion on the risk of strong earthquakes in the future in west of Chinese mainland [J ]. Plateau Earthquake Research, 2008,20 (2) : 4 ～10．
[13] 常利军,王椿镛,丁志峰,等.青藏高原东北缘上地幔各向异性研究[J].地球物理学报,2008,51(2) :431～438． Chang L J,Wang C Y,Ding Z F, et al. Seismic anisotropy of upper mantle in the northeastern margin of the Tibetan Plateau[J]. Chinese J. Geophys. (in Chinese), 2008,51(2) :431～438．
[14] 徐纪人,赵志新,石川有三.中国大陆地壳应力场与构造运动区域特征研究[J].地球物理学报,2008,51(3) :770～781． Xu J R, Zhao Z X, Ishikawa Yuzo. Regional characteristics of crustal stress field and tectonic motions in and around Chinese mainland[J]. Chinese J. Geophys. (in Chinese),2008, 51(3) :770～781．
[15] 陈祖安,林邦慧,白武明.1997年玛尼地震对青藏川滇地区构造块体系统稳定性影响的三维DDA+FEM方法数值模拟[J].地球物理学报,2008,51(5) :1422～1430． Chen Z A, Lin B H, Bai W M. 3-D numerical simulation on influence of 1997 Mani earthquake occurrence to stability of tectonic blocks system in Qingzang and Chuandian zone using DDA+FEM method[J]. Chinese J. Geophys. (in Chinese), 2008, 51(5) :1422～1430．
[16] 周仕勇.川西及邻近地区地震活动性模拟和断层间相互作用研究[J].地球物理学报,2008,51(1) :165～174． Zhou S Y. Seismicity simulation in Western Sichuan of China based on the fault interactions and its implication on the estimation of the regional earthquake risk[J]. Chinese J.Geophys. (in Chinese), 2008, 50(1) : 165～174．
[17] 高孟潭,周本刚,潘华.“5·12”汶川特大地震灾害特点及其防灾启示[J].震灾防御技术,2008,3(3) :209～215． Gao M T, Zhou B G, Pan H. Damage characteristics and enlightenment of disaster prevention of " 5． 12" Wenchuan earthquake [ J ]. Technology for Earthquake Disaster Prevention, 2008,3 (3) : 209 ～ 215．
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