2006年文安M_w4.9级地震的有限震源波形模拟研究
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摘要
2006年7月4日发生在河北文安的M_w4.9级地震,由于没有地表破裂并缺乏能够精确定位的余震序列,从而在地震发震构造的确定上存在困难.本文利用首都圈地震台网9个台站的Z分量数字波形记录,通过与有限震源模型的理论波形模拟结果比较,能够快速分辨发震断层面及破裂扩展方式,同时对震源运动学参数提供一定约束.结果显示,在文安地震震源机制解的两组共轭节面中,走向110°、倾角65°、滑动角8°的节面更有可能代表真实的发震面;破裂扩展方式为一向西扩展的单侧破裂.这一结果与本区域构造应力研究及块体相对运动方向观测结果一致.本文的工作,为中等震级地震发震构造的快速确定提出了一种简单而有效的方法.
Based on Z-component records of 9 stations in Beijing metropolitan digital Seismic Network (BSN), we analyzed the finite-source effect of the 2006 Wen'an M_w4. 9 earthquake, identified the actual rupture plane, and discussed the tectonic implications of our results. Due to the absence of surface rupture, the lack of connection between the source and known faults in the region, and the paucity of aftershocks, it has been difficult to identify the actual rupture plane of the Wen an earthquake. To tackle this problem, here we present a simple and efficient approach to resolving the fault-plane ambiguity and probing the kinematic source properties by modeling the waveforms in realistic three-dimensional structures from finite-source models. Between the two conjugate planes in the focal mechanism solution, we found that the one with a 110° strike is the likely rupture plane. We also determined that the overall source process is a westward unilateral rupture. These results are consistent with regional tectonic stress trend and the observed relative movement of tectonic blocks.
Based on Z-component records of 9 stations in Beijing metropolitan digital Seismic Network (BSN), we analyzed the finite-source effect of the 2006 Wen'an M_w4. 9 earthquake, identified the actual rupture plane, and discussed the tectonic implications of our results. Due to the absence of surface rupture, the lack of connection between the source and known faults in the region, and the paucity of aftershocks, it has been difficult to identify the actual rupture plane of the Wen an earthquake. To tackle this problem, here we present a simple and efficient approach to resolving the fault-plane ambiguity and probing the kinematic source properties by modeling the waveforms in realistic three-dimensional structures from finite-source models. Between the two conjugate planes in the focal mechanism solution, we found that the one with a 110° strike is the likely rupture plane. We also determined that the overall source process is a westward unilateral rupture. These results are consistent with regional tectonic stress trend and the observed relative movement of tectonic blocks.
引文
[1] 刁桂苓.张四昌,孙佩卿等.2006年7月4日文安5． 1级地震.地震地质,2006,28(3) :497～502DiaoG L,Zhang S C,Sun P Q,et al.The M5． 1 Wen'an earthquake of July 4,2006． Seismology and Geology (in Chinese),2006,28(3) :497～～502
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[11] Olsen K B,DaySM,BradleyC R.Estimation of Q for longperiod (>2 s) waves in the Los Angeles Basin.Bull.Seis.Soc.Am.,2003,93(2) :627～638
[12] Sun R,Liu F,Chen H.Structural setting of strong earthquakes in the Huabei area of China.Pure Appl.Geophys.,2001,158:903～～918
[13] Zhao L,Chen P,Jordan T H.Strain Green's tensors,reciprocity and their applications to seismic source and structure studies.Bull.Seismol.Soc.Am.,2006,96 (5) :1753～1763
[14] 国家地震局.中国岩石圈动力学地图集.北京:中国地图出版社,1989State Seismological Bureau.Lithosphere Dynamics Atlas of China (in Chinese).Beijing:SinoMaps Press,1989
[15] 李钦祖.华北地壳应立场的基本特征.地球物理学报,1980, 23(4) :376～388Li Q Z.General features of the stress fields in the crust of North China.Chinese J.Geophys.(in Chinese),1980,23 (4) :376～388
[16] Xu Z,Wang S,Huang Y,et al.Tectonic stress field of China inferred from a large number of small earthquakes.J.Geophys.Res.,1992,97(B8) :11867～11877
[17] 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
[18] 李松林,张先康,宋占隆等.多条人工地震测深剖面资料联合反演首都圈三维地壳结构.地球物理学报,2001,44(3) : 360～369Li S L,Zhang X K,Song Z L,et al.Three-dimensional crustal structure of the capital area obtained by a joint inversion of DSS data from multiple profiles.Chinese J.Geophys.(in Chinese),2001,44(3) :360～369
[19] 嘉世旭,张先康.华北不同构造块体地壳结构及其对比研究.地球物理学报,2005,48(3) :611～620Jia S X,Zhang X K.Crustal structure and comparison of different tectonic blocks in North China.Chinese J.Geophys.(in Chinese),2005,48(3) :611～620
[2] 黄建平,倪四道,傅容珊等.综合近震及远震波形反演2006文安地震(M_w5． 1) 的震源机制解.地球物理学报,2009,52 (1) :120～130Huang J P,Ni S D,Fu R S,et al.Source mechanism of the 2006 M_w5． 1 Wen' an earthquake determined from a joint inversion of local and teleseismic broadband waveform data.Chinese J.Geophys.(in Chinese),2009,52(1) :120～ 130
[3] Zhou S Y,Chen X F,Irikura K.Analysis on the reliability and resolution of the earthquake source history inferred from waveforms taking ChiChi earthquake as an example.Geophys.J.Int.,2004,157:1217～1232
[4] Boatwright J L.The nature of the earthquake focus as inferred from body-wave observations[Ph.D.thesis].New York:Columbia Univ.,1999
[5] Mori J,Hartzell S.Source inversion of the 1988 upland,California,earthquake:determination of a fault plane for a small event.Bull.Seismol.Soc.Am.,1990,80(3) :507～518
[6] ChenYT,Xu LS,Li X,et al.Source process of the 1990 Gonghe,China,earthquake and tectonic stress field in the northeastern Qinghai Xizang (Tibetan) plateau.Pure Appl.Geophys.,1996,146(3 4) :697～715
[7] McGuire J.Estimating finite source properties of small earthquake ruptures.Bull.Seismol.Soc.Am.,2004,94 (2) :377～393
[8] Chen P,Zhao L,Jordan T H.Finite moment tensor of the 3 September 2002 Yorba Linda earthquake.Bull.Seismol.Soc.Am.,2005,95(3) .:1170～1180
[9] Wells D L,Coppersmith K J.New empirical relationships among magnitude,rupture length,rupture width,rupture area,and surface displacement.Bull.Seismol.Soc.Am.,1994,84(4) :974～1002
[10] Olsen K B.Simulation of three dimensional wave propagation in the Salt Lake Basin[Ph.D.thesis].Salt Lake City:University of Utah,1994
[11] Olsen K B,DaySM,BradleyC R.Estimation of Q for longperiod (>2 s) waves in the Los Angeles Basin.Bull.Seis.Soc.Am.,2003,93(2) :627～638
[12] Sun R,Liu F,Chen H.Structural setting of strong earthquakes in the Huabei area of China.Pure Appl.Geophys.,2001,158:903～～918
[13] Zhao L,Chen P,Jordan T H.Strain Green's tensors,reciprocity and their applications to seismic source and structure studies.Bull.Seismol.Soc.Am.,2006,96 (5) :1753～1763
[14] 国家地震局.中国岩石圈动力学地图集.北京:中国地图出版社,1989State Seismological Bureau.Lithosphere Dynamics Atlas of China (in Chinese).Beijing:SinoMaps Press,1989
[15] 李钦祖.华北地壳应立场的基本特征.地球物理学报,1980, 23(4) :376～388Li Q Z.General features of the stress fields in the crust of North China.Chinese J.Geophys.(in Chinese),1980,23 (4) :376～388
[16] Xu Z,Wang S,Huang Y,et al.Tectonic stress field of China inferred from a large number of small earthquakes.J.Geophys.Res.,1992,97(B8) :11867～11877
[17] 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
[18] 李松林,张先康,宋占隆等.多条人工地震测深剖面资料联合反演首都圈三维地壳结构.地球物理学报,2001,44(3) : 360～369Li S L,Zhang X K,Song Z L,et al.Three-dimensional crustal structure of the capital area obtained by a joint inversion of DSS data from multiple profiles.Chinese J.Geophys.(in Chinese),2001,44(3) :360～369
[19] 嘉世旭,张先康.华北不同构造块体地壳结构及其对比研究.地球物理学报,2005,48(3) :611～620Jia S X,Zhang X K.Crustal structure and comparison of different tectonic blocks in North China.Chinese J.Geophys.(in Chinese),2005,48(3) :611～620
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