GPS观测结果反映的尼泊尔M_w7.8地震孕震特征
详细信息 本馆镜像全文    |  推荐本文 | | 获取馆网全文
摘要
针对2015年4月25日尼泊尔Mw7.8地震的孕震特征,本文首先对覆盖尼泊尔及周边地区的5套GPS水平速度场结果进行了融合,得到了近似统一参考框架下的速度场结果;在此基础上通过对此次地震震源区及周边地区的速度场、应变率场、基线时间序列分析,识别了震前变形特征.GPS应变率场结果显示,喜马拉雅主边界断裂存在大范围挤压应变积累,震源区处于近南北向应变积累高值过渡区.跨喜马拉雅构造带的GPS基线时间序列结果表现为持续缩短现象,表明印度板块与欧亚板块之间的持续挤压变形特征,2012年以来的缩短增强现象反映了印度板块对青藏块体的推挤增强作用明显.距离震中较近的西藏南部GPS同震位移结果以南向运动为主且指向震中,反映了青藏高原存在逆冲应变释放现象.综合此次尼泊尔地震前变形和同震应变释放特征,认为此次地震的孕震区域和同震应变释放区域均较大,将会对青藏高原的地壳变形与强震孕育产生深远影响.
On April 25,2015,an Mw7.8earthquake hit Nepal,causing serious casualties.In order to recognize the seismogenic process of this event,this work analyzed the pre-seismic and co-seismic crustal deformation in Nepal and adjacent regions.The parameters involved include the GPS horizontal velocity field,strain rate field,GPS baseline time series and the coseismic displacements in the Tibet plateau.Firstly,we collected 5sets of the GPS horizontal velocity field covering Nepal and adjacent areas,and then transformed them to an approximately unified reference frame.Secondly,we calculated GPS strain rate fields in the seismic source and its vicinity using the least square collocation method on a sphere surface,and analyzed their characteristics.Thirdly,we analyzed the dynamic changes of long baselines of IISC-LHAS,IISC-DLHA,which cross the Himalayan.Finally,the coseismic displacements were obtained through processing the GPS data of 22 April to 24 April and 26 April to 28 April,respectively.The GPS strain rate field shows that regional compressive strain accumulated on a large scale around the Main Boundary Thrust of the Himalayan tectonic zone,and the huge earthquake occurred in the region between two high-value areas of the N-S directed strain.GPS geodesic time-series indicates the baselines across the Himalaya shortened continuously,implying continuous extrusional deformation between the Indian and the Eurasian plates.The phenomena that the shortening enhanced after the year 2012 reflects the extruding force from the Indian plate has been strengthened.The co-seismic displacements recorded by the permanent GPS stations in Tibet neighboring Nepal are dominantly directed to south,just towards the epicenter,likely resulting from the release of thrust strain in southern Tibet.From the feature of pre-seismic and coseismic crustal deformation of the Nepal great shock,we suggest that both its seismogenic and co-seismic strain release areas are relatively large,which would generate long-term impact on the Tibetan Plateau,such as dynamic adjustment in the crust or even to trigger unlocking of the Himalayan thrusts to spawn big quakes.
引文
Ader T,Avouac J P,Jing L Z,et al.2012.Convergence rate acrossthe Nepal Himalaya and interseismic coupling on the MainHimalayan Thrust:Implications for seismic hazard.Journal ofGeophysical Research,117,B04403,doi:10.1029/2011JB009071.
    Bettinelli P,Avouac J P,Flouzat M,et al.2006.Plate motion ofIndia and interseismic strain in the Nepal Himalaya from GPSand DORIS measurements.Journal of Geodesy,80(8-11):567-589.
    Bilham R,Larson K,Freymueller J.1997.GPS measurements ofpresent-day convergence across the Nepal Himalaya.Nature,386(6620):61-64.
    Chen G Q,Wu Y Q,Jiang Z S,et al.2013.Characteristics ofseismogenic model of Mw9.0 earthquake in Tohoku,Japanreflected by GPS data.Chinese J.Geophys.(in Chinese),53(5):848-856,doi:10.6038/cjg20130314.
    Chen Q Z,Freymueller J T,Wang Q,et al.2004.A deformingblock model for the present-day tectonic of Tibet.Journal ofGeophysical Research,109:B01403,doi:10.1029/2002JB002151.
    China Earthquake Administration.2015.《The atlas of Mw7.8earthquakein Nepal occurred on April 25,2015》.http:∥eqxiu.com/s/LXU4nA8y?eqrconde=1[2015-5-13].
    Deng Q D,Cheng S P,Ma J,et al.2014.Seismic activities andearthquake potential in the Tibetan Plateau.Chinese Journalof Geophysics(in Chinese),57(7):2025-2042,doi:10.6038/cjg20140701.
    Feldl N,Bilham R.2006.Great Himalayan earthquakes and theTibetan plateau.Nature,444(7116):165-170.
    Gan W J,Zhang P Z,Shen Z K,et al.2007.Present-day crustalmotion within the Tibetan Plateau inferred from GPS measurements.Journal of Geophysical Research,112:B08426,doi:10.1029/2005JB004120.
    Institute of Geophysics,China Earthquake Administration.2015.《The Mw7.8earthquake in Nepal occurred on April 25,2015》.http:∥www.cea-igp.ac.cn/tpxw/272110.shtml[2015-5-13].
    Jiang Z S,Fang Y,Wu Y Q,et al.2009.The dynamic process ofregional crustal movement and deformation before WenchuanMs8.0earthquake.Chinese J.Geophys.(in Chinese),52(2):505-518.
    Jiang Z S,Liu J N.2010.The method in establishing strain fieldand velocity field of crustal movement using least squarescollocation.Chinese J.Geophys.(in Chinese),53(5):1109-1117,doi:10.3969/j.issn.0001-5733.2010.05.011.
    Liang S M,Gan W J,Shen C Z,et al.2013.Three-dimensionalvelocity field of present-day crustal motion of the TibetanPlateau derived from GPS measurements.Journal of GeophysicalResearch:Solid Earth,118,doi:10.1002/2013JB010503.
    Ponraj M,Miura S,Reddy C D,et al.2010.Estimation of straindistribution using GPS measurements in the Kumaun region ofLesser Himalaya.Journal of Asian Earth Science,39(6):658-667.
    USGS,2015.M7.8-34km ESE of Lamjung,Nepal,http:∥earthquake.usgs.gov/earthquakes/eventpage/us20002926[2015-05-12].
    Ward S N.1994.A multidisciplinary approach to seismic hazard insouthern California.Bulletin of the Seismological Society ofAmerica,84(5):1293-1309.
    Wang Q,You X Z,Wang W Y,et al.1998.GPS measurement andcurrent crustal movement across the Himalaya.Crustal Deformationand Earthquake(in Chinese),18(3):43-50.
    Wang Q,Zhang P Z,Freymueller J T,et al.2001.Present-daycrustal deformation in China constrained by global positioningsystem measurements.Science,294(5542):574-577.
    Wu Y Q,Jiang Z S,Yang G H,et al.2011.Comparison of GPSstrain rate computing methods and their reliability.GeophysicalJournal International,185(2):703-717,doi:10.1111/j.1365-246X.2011.04976.x.
    Wu Y Q,Jiang Z S,Yang G H,et al.2009.The application andmethod of GPS strain calculation in whole mode using squarecollocation in sphere surface.Chinese J.Geophys.(inChinese),52(7):1707-1711,doi:10.3969.issn.00015733.
    Wu Y Q,Jiang Z S,Zhao J,et al.2015.Crustal deformation beforethe 2008Wenchuan Ms8.0earthquake studied using GPS data.Journal of Geodynamics,85:11-23.
    Xiao G R.2011.GPS crustal deformation observations and itsapplication in the great triangular seismotectonic[Ph.D.thesis](in Chinese).Beijing:Institute of Geology,China EarthquakeAdministration.
    Zhang P Z,Deng Q D,Zhang G M,et al.2003.Active-tectonicblocks and strong earthquakes in the continent of China.ScienceinChina(Series D),46(S2):13-24.
    陈光齐,武艳强,江在森等.2013.GPS资料反映的日本东北Mw9.0地震的孕震特征.地球物理学报,56(3):848-856,doi:10.6038/cjg20130314.
    邓起东,程绍平,马冀等.2014.青藏高原地震活动特征及当前地震活动形势.地球物理学报,57(7):2025-2042,doi:10.6038/cjg20140701.
    江在森,方颖,武艳强等.2009.汶川8.0级地震前区域地壳运动与变形动态过程.地球物理学报,52(2):505-518.
    江在森,刘经南.2010.应用最小二乘配置建立地壳运动速度场与应变场的方法.地球物理学报,53(5):1109-1117,doi:10.3969/j.issn.0001-5733.2010.05.011.
    王琪,游新兆,王文颖等.1998.跨喜马拉雅的GPS观测与地壳形变.地壳形变与地震,18(3):43-50.
    武艳强,江在森,杨国华等.2009.利用最小二乘配置在球面上整体解算GPS应变场的方法及应用.地球物理学报,52(7):1707-1711,doi:10.3969.issn.00015733.
    肖根如.2011.GPS地壳形变观测及其在中亚大三角地震构造域的应用[博士论文].北京:中国地震局地质研究所.
    张培震,邓起东,张国民等.2003.中国大陆的强震活动与活动地块.中国科学(D辑),33(S1):12-20.
    中国地震局.2015.《2015年4月25日尼泊尔8.1级地震图集》.http:∥eqxiu.com/s/LXU4nA8y?eqrconde=1[2015-5-13].
    中国地震局地球物理研究所.2015.《2015年4月25日尼泊尔8.1级地震》.http:∥www.cea-igp.ac.cn/tpxw/272110.shtml[2015-5-13].

版权所有:© 2023 中国地质图书馆 中国地质调查局地学文献中心