利用矩张量反演法研究江苏高邮—宝应M_S4.9级地震震源机制解和震源深度
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摘要
基于江苏、安徽、山东和浙江等省区域台网共19个宽频带数字台站的地震波形,采用HypoDD双差定位方法确定了2012年7月20日江苏高邮—宝应MS4.9级地震震中位置,再利用时间域矩张量反演法TDMT_INV获得了其震源机制解和震源深度.反演结果显示:最佳双力偶解为节面Ⅰ走向290°,倾角88°,滑动角-21°;节面Ⅱ走向21°,倾角69°,滑动角-177°,地震矩震级为MW4.95,震源深度约为7~9km.利用滑动时窗相关法提取sPn震相测定震源深度为8.95km,两者一致性较好.随后不同地壳模型和不同震中定位误差对反演结果的影响试验揭示了反演结果具有稳定性.通过以下几种分析:1与利用CAP(Cut and Paste)矩张量反演法得到的结果进行对比;2P波初动投影;3正反演试验探求反演结果不稳定的影响因素等方法,验证了反演结果的可靠性.综合本文研究成果、震后科学考察结果(包括重力测量和地震烈度分布图)及现有的地质构造资料,推测此次地震的发震构造为杨汊仓—桑树头断裂,节面Ⅱ为断层面,是一个右旋走滑兼有少量正断层性质的错动.
An MS4.9earthquake occurred in Gaoyou-Baoying,Jiangsu on 20 July 2012.This work determined its focal mechanism and depth through Time Domain Moment Tensor Inversion(TDMT-INV),and analyzed the stability and reliability of the results.Based on the 19 regional broadband seismometers′waveforms from Jiangsu,Anhui,Shandong and Zhejiang seismic networks,we accurately determined the location of the earthquake by theHypoDD first,and then calculated its focal mechanism and depth through TDMT_INV.And we compared this depth that obtained from picking up the sPn phase by patterning correlation coefficients in sliding windows.We tested the results through the following several procedures:1 Experiments by different crustal models and different epicenter location errors;2 Comparing with the result from the CAP method;3 P-wave first motions are projected onto the focal sphere;4 Forward modeling and inversion to research the factors of inversion instability.The nodal plane parameters of the best double-couple focal mechanism are as follows:strike290°,dip 88°and rake-21°;or strike 21°,dip 69°and rake-177°,Mw4.95 and focal depth is 7~9km.We calculated the focal depth by picking up sPn phase and got the 8.95 km result.The results include:1 All angles match well except one dip with 20°variation when we used the Crust2.0model instead of the IASP91 and hold the Q value unchanged.The results are nearly invariable if Q value changes by 100 and holding velocity and density constant.The maximum misalignment of the result is 6°when the epicenter varies within 5km.The result will deviate from the best solution while the epicenter varies by 10 km.2 The predominant focal depth is 8~10km by the CAP method.The results for 8km-focal depth are:strike 19°,dip 65°and rake-180°.3 There are 41 P-wave first motions projected onto the focal sphere,the ratio of inconsistent polarity is 7.3%,and all the contradictions are distributed around the nodal plane.4By forward modeling and inversion,while using the TDMT_INV method to invert the nearly pure strike-slip fault,we proved that the sign of slip will probably reverse if the station distribution concentrates on both ends of the field angle,the inversion results can properly return the forward model while the stations are distributed uniformly.In this case,it is hard to determine the accurate result through the evaluation parameters variance reduction(VR)and the variance divided by the percent double-couple(RES/Pdc).The TDMT_INV method is less dependent on the crustal model.The inversion results do not change much if the epicenter error is within 5km.The method has stability,but stations should surround the epicenter and are distributed uniformly as much as possible while inverting the near pure strike-slip fault.By comparing our results with field investigations after the earthquake(gravity measurement and seismic intensity distribution)and existing data of geological structure,we infer that the seismogenic structure for this event is the Yangchacang-Sangshutou fault,which is of right-lateral strike slip with a small normal component.
引文
Bassin C,Laske G,Masters G.2000.The current limits ofresolution for surface wave tomography in North America.EOSTrans AGU,81,F897.
    Brandt M B C,Saunders I.2011.New regional moment tensors inSouth Africa.Seismological Research Letters,82(1):69-80.
    Braunmiller J,Nábelek J.2002.Seismotectonics of the explorerregion.Journal of Geophysical Research,107(B10):ETG1-1-ETG1-25.
    Chen A D.2001.Dynamic mechanism of formation of dustpansubsidence,Northern Jiangsu.Geological Journal of ChinaUniversities(in Chinese),7(4):408-418.
    Dreger D S,Helmberger D V.1993.Determination of sourceparameters at regional distances with three-component sparsenet work data.Journalof GeophysicalResearch,98(B5):8107-8125.
    Dreger D S.1994.Empirical Green's function study of the January17,1994 Northridge,California earthquake.GeophysicalResearch Letters,21(24):2633-2636.
    Dreger D S,Ritsema J,Pasyanos M.1995.Broadband analysis ofthe 21September,1993 Klamath Falls earthquake sequence.Geophysical Research Letters,22(8):997-1000.
    Dreger D S.1997.The large aftershocks of the Northridgeearthquake and their relationship to mainshock slip and faultzone complexity.Bulletin of the Seismological Society ofAmerica,87(5):1259-1266.
    Dreger D,Uhrhammer R,Pasyanos M,et al.1998.Regional andfar-regional earthquake locations and source parameters usingsparse broadband networks:A test on the Ridgecrest sequence.Bulletin of the Seismological Society of America,88(6):1353-1362.
    Dreger D S.2003.Time-domain moment tensor inverse code(TDMT-INVC)Release 1.1.International Handbook ofEarthquake and Engineering Seismology,Vol.B:1627.
    Fang M S,Du A L,Dong X P,et al.1995.Determination of focaldepth with the sPn phase.Seismological and GeomagneticObservation and Research(in Chinese),16(5):13-18.
    Herrmann R B,Benz H,Ammon C J.2011.Monitoring theEarthquake Source Process in North America.Bulletin of theSeismological Society of America,101(6):2609-2625.
    Hong D Q,Wang X Z,Ni H Y,et al.2013.Focal mechanism andfocal depth of July 20,2012Jiangsu Gaoyou Ms4.9earthquake.Progress in Geophys.(in Chinese),28(4):1757-1765,doi:10.6038/pg20130416.
    Huang M H,Dreger D,Bürgmann R,et al.2013.Joint inversionof seismic and geodetic data for the source of the 2010March 4,Mw6.3Jia-Shian,SW Taiwan,earthquake.Geophys.J.Int.,193(3):1608-1626.
    Jost M L,Herrmann R B.1989.A student′s guide to and review ofmoment tensors.Seism.Res.Lett.,60(2):37-57.
    Kao H,Jian P R,Ma K F,et al.1998.Moment-tensor inversionfor offshore earthquakes east of Taiwan and their implications toregional collision.Geophysical Research Letters,25(19):3619-3622.
    Kawakatsu H.1998.On the realtime monitoring of the long-periodseismic wavefield.Bull.Earthquake Res.Inst.,73:267-274.
    Kennett B L N,Engdahl E R.1991.Traveltimes for globalearthquake location and phase identification.Geophys.J.Int.,105(2):429-465.
    Kind R.1979.Observation of sPn from Swabian Alb earthquake atthe GRF array.Journal of Geophysics,45:337-340.
    Laurent S,Davidowitz H.1994.Encoding of olfactory informationwith oscillating neural assemblies.Science,265(5180):1872-1875.
    Laurent S,Wehr M,Davidowitz H.1996.Temporal representations ofodors in an olfactory network.The Journal of Neuroscience,16(12):3837-3847.
    Liu J D,Yang W L,Li L M,et al.2012.Damage survey andanalysis on earthquake(Ms=4.9)at the boundary zone ofGaoyou and Baoying,Jiangsu Province.Earthquake Research inChina(in Chinese),28(4):402-414.
    Minson S E,Dreger D S.2008.Stable inversions for completemoment tensors.Geophys.J.Int.,174(2):585-592.
    Neng Y,Yang Q,Zhang K X,et al.2009.Tectonic subsidence andevolution of the Gaoyou depression in northern Jiangsu Basinduring the Late Cretaceous to the Cenozoic.SedimentaryGeology and Tethyan Geology(in Chinese),29(2):25-32.
    Pasyanos M E,Dreger D S,Romanowicz B.1996.Toward real-timeestimation of regional moment tensors.Bulletin of theSeismological Society of America,86(5):1255-1269.
    Patton H J,Zandt G.1991.Seismic moment tensors of western U.S.earthquakes and implications for the tectonic stress field.Journal of Geophysical Research,96(B11):18245-18259.
    Ratchkovski N A,Hansen R A.2002.New constraints on tectonicsof interior Alaska:Earthquake locations,source mechanisms,and stress regime.Bulletin of the Seismological Society ofAmerica,92(3):998-1014.
    Ristau J,Rogers G C,Cassidy J F.2007.Stress in western Canadafrom regional moment tensor analysis.Canadian Journal ofEarth Sciences,44(2):127-148.
    Saikia C K.1994.Modified frequency-wavenumber algorithm forregional seismograms using Filon′s quadrature:modelling of Lgwaves in eastern North America.Geophys.J.Int.,118(1):142-158.
    Tajima F,Megnin C,Dreger D S,et al.2002.Feasibility of realtime broadband waveform inversion for simultaneous momenttensor and centroid location determination.Bulletin of theSeismological Society of America,92(2):739-750.
    Tang L L,Zhao C P,Wang H T.2012.Study on the sourcecharacteristics of the 2008 Ms6.8 Wuqia,Xinjiang earthquakesequence and the stress field on the northeastern boundary ofPamir.Chinese J.Geophys.(in Chinese),55(4):1228-1239,doi:10.6038/j.issn.0001-5733.2012.04.018.
    Tu H W,Wang H T,Zhao C P,et al.2008.Using long periodbody wave to inverse moment tensors of Xinjiang Jiashi M6.8earthquake in 2003and mid-small earthquake before and afterthe earthquake.Journal of Seismological Research(in Chinese),31(1):7-13.
    Waldhauser F,Ellsworth W L.2000.A double-differenceearthquake location algorithm:Method and application to theNorthern Hayward fault,California.Bulletin of the SeismologicalSociety of America,90(6):1353-1368.
    Wang Q C,Chen Z L,Zheng S H.2009.Spatial segmentationcharacteristic of focal mechanism of aftershock sequence ofWenchuan Earthquake.Chinese Sci.Bull.,54(16):2263-2270.
    Wu X Y,Xia L J,Chen J.2009.Further cognition of the Gaoyousag in the Subei basin and its significance on oil and gasexploration.Petroleum Geology&Experiment(in Chinese),31(6):571-575.
    Zhang K X,Qi J F,Ren H M,et al.2008.Study on faultsevolution in Gaoyou Fault Depression of Subei Basin.PetroleumGeology&Oilfield Development in Daqing(in Chinese),27(2):21-24.
    Zhao C P,Chen Z L,Zheng S H,et al.2008.Moment inversion ofmoderate earthquakes and the locally perturbed stress field inthe Jiashi source region.Chinese J.Geophys.(in Chinese),51(3):782-792.
    Zhao L S,Helmberger D V.1994.Source estimation frombroadband regional seismograms.Bulletin of the SeismologicalSociety of America,84(1):91-104.
    陈安定.2001.苏北箕状断陷形成的动力学机制.高校地质学报,7(4):408-418.
    房明山,杜安陆,董孝平等.1995.用sPn震相测定近震震源深度.地震地磁观测与研究,16(5):13-18.
    洪德全,王行舟,倪红玉等.2013.多种方法研究2012年7月20日江苏高邮Ms4.9级地震震源机制解和震源深度.地球物理学进展,28(4):1757-1765,doi:10.6038/pg20130416.
    刘建达,杨伟林,李丽梅等.2012.江苏高邮—宝应交界4.9级地震震害分析.中国地震,28(4):402-414.
    能源,杨桥,张克鑫等.2009.苏北盆地高邮凹陷晚白垩世一新生代构造沉降史分析与构造演化.沉积与特提斯地质,29(2):25-32.
    唐兰兰,赵翠萍,王海涛.2012.2008年新疆乌恰6.8级地震序列震源特征及帕米尔东北缘应力场研究.地球物理学报,55(4):1228-1239,doi:10.6038/j.issn.0001-5733.2012.04.018.
    屠泓为,王海涛,赵翠萍等.2008.利用长周期体波反演2003年伽师6.8级地震及其前后中小地震矩张量.地震研究,31(1):7-13.
    王勤彩,陈章立,郑斯华.2009.汶川大地震余震序列震源机制的空间分段特征.科学通报,54(16):2348-2354.
    吴向阳,夏连军,陈晶.2009.苏北盆地高邮凹陷构造再认识及对油气勘探的意义.石油实验地质,31(6):571-575.
    张克鑫,漆家福,任红民等.2008.苏北盆地高邮凹陷断层演化规律研究.大庆石油地质与开发,27(2):21-24.
    赵翠萍,陈章立,郑斯华等.2008.伽师震源区中等强度地震矩张量反演及其应力场特征.地球物理学报,51(3):782-792.
    1)江苏省地震局.2012.2012年7月20日江苏高邮、宝应交界M4.9地震灾害评估报告.

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