四川芦山7.0级地震及其与汶川8.0级地震的关系
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摘要
2013年4月20日在四川省雅安市芦山县发生M7.0级地震.根据四川省台网资料和收集的国内外相关资料,我们分析了芦山地震的基本参数、余震分布、序列衰减等特征.结果表明:芦山地震位于龙门山断裂南段,其震源力学机制显示为纯逆冲性质,与龙门山断裂构造特征相符合;芦山地震的余震较丰富,震后15天震区已发生7800多次余震,其中,5级以上余震4次,最大余震是4月21日17时5分芦山、邛崃交界M5.4级地震;余震分布形成的图形显示其长轴走向与龙门山断裂构造走向一致,余震分布显示密集区长轴约40km,短轴约20km.与汶川M8.0级地震在震源力学机制、破裂过程、余震空间展布以及地表破裂等对比分析后表明:芦山地震与汶川地震的震源错动类型、破裂过程、地表破裂以及余震活动等特征存在明显差异;芦山地震与汶川地震震中位置相距90km,两次地震的余震密集区相距50km;汶川8.0级地震造成龙门山断裂中北段较充分破裂,芦山7.0级地震则展布于龙门山断裂南段且破裂尺度有限;两者有发震构造上的联系,但两次地震是相对独立的地震事件.
On 20 April 2013 an M7.0 Lushan earthquake in the Sichuan of China occurred on the southern segment of the Longmenshan fault.According to the data of the telemeter seismographic network in Sichuan and the current correlative information from internal and overseas,we analyze the basic earthquake parameters,aftershock distribution,sequence attenuation characteristics.Our results show that the focal mechanisms of the Lushan earthquake result from a pure thrust and are consistent with the characteristics of Longmenshan fault structure.The Lushan earthquake is rich in aftershocks.More than 7800 aftershocks are logged since main-quake from 20 April to 5 May,2013.4 aftershocks of magnitude 5 or greater have occurred in the region.The largest aftershock is the M5.4 earthquake on April 21 at 17∶05 of Beijing time between Lushan and Qionglai counties.The long axis of aftershocks distribution ellipsoid is consistent with the Longmenshan fault structural trend.The lengths of the long and short axis of the aftershocks distribution ellipsoid are about 40 km and 20 km respectively.This indicates that the rupture scale of this earthquake is limited.From following aspects such as the focal mechanisms,the rupture process,aftershocks spatial distribution and the surface rupture,we compare the Lushan earthquake with the M8.0 Wenchuan earthquake and find that these two earthquakes are significantly different.The distance between the Lushan earthquake and the Wenchuan earthquake is about 90 km.The distance between two locations of the aftershock-intensive areas is 50 km.The Wenchuan earthquake made the middle-northern segment of the Longmenshan fault to rupture fully.The original location of the Lushan earthquake is in the southern segment of the Longmenshan fault.The rupture scale of the M7.0 event is limited.Although they are connected with each other on same seismogenic structure,they are two relatively independent seismic events.
On 20 April 2013 an M7.0 Lushan earthquake in the Sichuan of China occurred on the southern segment of the Longmenshan fault.According to the data of the telemeter seismographic network in Sichuan and the current correlative information from internal and overseas,we analyze the basic earthquake parameters,aftershock distribution,sequence attenuation characteristics.Our results show that the focal mechanisms of the Lushan earthquake result from a pure thrust and are consistent with the characteristics of Longmenshan fault structure.The Lushan earthquake is rich in aftershocks.More than 7800 aftershocks are logged since main-quake from 20 April to 5 May,2013.4 aftershocks of magnitude 5 or greater have occurred in the region.The largest aftershock is the M5.4 earthquake on April 21 at 17∶05 of Beijing time between Lushan and Qionglai counties.The long axis of aftershocks distribution ellipsoid is consistent with the Longmenshan fault structural trend.The lengths of the long and short axis of the aftershocks distribution ellipsoid are about 40 km and 20 km respectively.This indicates that the rupture scale of this earthquake is limited.From following aspects such as the focal mechanisms,the rupture process,aftershocks spatial distribution and the surface rupture,we compare the Lushan earthquake with the M8.0 Wenchuan earthquake and find that these two earthquakes are significantly different.The distance between the Lushan earthquake and the Wenchuan earthquake is about 90 km.The distance between two locations of the aftershock-intensive areas is 50 km.The Wenchuan earthquake made the middle-northern segment of the Longmenshan fault to rupture fully.The original location of the Lushan earthquake is in the southern segment of the Longmenshan fault.The rupture scale of the M7.0 event is limited.Although they are connected with each other on same seismogenic structure,they are two relatively independent seismic events.
引文
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[12]中国地震局地震预测研究所地震学室.2013年4月20日四川省芦山7.0级地震震源机制解.http:∥www.seis.ac.cn/.
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[14]赵翠萍,陈章立,周连庆等.汶川Mw8.0级地震震源破裂过程研究:分段特征.科学通报,2009,54(22):3475-3482.Zhao C P,Chen Zh L,Zhou L Q,et al.Rupture process ofthe Wenchuan Mw8.0earthquake of Sichuan,China:thesegmentation feature.Chinese Science Bulletin,2010,55(3):284-292.
[2]中国地震局地质研究所.四川省芦山7.0级强震:一次典型的盲断层型地震.http:∥www.eq-igl.ac.cn/.
[3]张勇,许力生,陈运泰.芦山4.20地震破裂过程及其致灾特征初步分析.地球物理学报,2013,56(4):1408-1411,doi:10.6038/cjg20130435.Zhang Y,Xu L S,Chen Y T.Rupture process of the Lushan4.20earthquake and preliminary analysis on the disaster-causing mechanism.Chinese J.Geophys.(in Chinese),2013,56(4):1408-1411,doi:10.6038/cjg20130435.
[4]王卫民,郝金来,姚振兴.2013年4月20日四川芦山地震震源破裂过程反演初步结果.地球物理学报,2013,56(4):1412-1417,doi:10.6038/cjg20130436.Wang W M,Hao J L,Yao Z X.Preliminary result forrupture process of Apr.20,2013,Lushan Earthquake,Sichuan,China.Chinese J.Geophys.(in Chinese),2013,56(4):1412-1417,doi:10.6038/cjg20130436.
[5]郑勇,刘成利,熊熊.雅安地震的动态破裂过程模型.中国科学院测量与地球物理研究所.http:∥www.whigg.ac.cn/.
[6]徐锡伟,陈桂华,于贵华等.5.12汶川地震地表破裂基本参数的再论证及其构造内涵分析.地球物理学报,2010,53(10):2321-2336,doi:10.3969/j.issn.0001-5733.2010.10.006.Xu X W,Chen G H,Yu G H,et al.Reevaluation of surfacerupture parameters of the 5.12Wenchuan earthquake and itstectonic implication for Tibetan uplift.Chinese J.Geophys.(inChinese),2010,53(10):2321-2336,doi:10.3969/j.issn.0001-5733.2010.10.006.
[7]周荣军,黄润秋,雷建成等.四川汶川8.0级地震地表破裂与震害特点.岩石力学与工程学报,2008,27(11):2173-2183.Zhou R J,Huang R Q,Lei J C,et al.Surface rupture andhazard characteristics of Wenchuan earthquake with magnitude8.0in Sichuan.Chinese Journal of Rock Mechanics andEngineering(in Chinese),2008,27(11):2173-2183.
[8]Zhao L S,Helmberger D V.Source estimation frombroadband regional seismograms.Bull.Seismol.Soc.Amer.,1994,84(1):91-104.
[9]Zhu L P,Helmberger D V.Advancement in source estimationtechniques using broadband regional seismograms.Bull.Seismol.Soc.Amer.,1996,86(5):1634-1641.
[10]郑勇,马宏生,吕坚等.汶川地震强余震(MS≥5.6)的震源机制解及其与发震构造的关系.中国科学D辑:地球科学,2009,39(4):413-426.Zheng Y,Ma H S,LüJ,et al.Source mechanism of strongaftershocks(MS≥5.6)of the 2008/05/12Wenchuan earthquakeand the implication for seismotectonics.Sciencein China(Series D),2009,52(6):739-753.
[11]曾祥方,罗艳,韩立波等.2013年4月20日四川芦山MS7.0地震:一个高角度逆冲地震.地球物理学报,2013,56(4):1418-1424,doi:10.6038/cjg20130437.Zeng X F,Luo Y,Han L B,et al.The Lushan MS7.0earthquake on 20 April 2013:A high-angle thrust event.Chinese J.Geophys.(in Chinese),2013,56(4):1418-1424,doi:10.6038/cjg20130437.
[12]中国地震局地震预测研究所地震学室.2013年4月20日四川省芦山7.0级地震震源机制解.http:∥www.seis.ac.cn/.
[13]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.Wang W M,Zhao L F,Li J,et al.Rupture process of theMs8.0 Wenchuan earthquake of Sichuan,China.Chinese J.Geophys.(in Chinese),2008,51(5):1403-1410.
[14]赵翠萍,陈章立,周连庆等.汶川Mw8.0级地震震源破裂过程研究:分段特征.科学通报,2009,54(22):3475-3482.Zhao C P,Chen Zh L,Zhou L Q,et al.Rupture process ofthe Wenchuan Mw8.0earthquake of Sichuan,China:thesegmentation feature.Chinese Science Bulletin,2010,55(3):284-292.
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