利用多台阵压缩传感方法反演尼泊尔M_W7.9地震破裂过程
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摘要
2015年4月25日,尼泊尔地区发生MW7.9地震,震中位于28.1°N,84.7°E.为了详细地研究此次破坏性极强的地震的破裂过程,本文利用多台阵压缩传感方法,使用了阿拉斯加、欧洲和澳大利亚三个台网的共计179个台站的远场P波垂直分量的数据来反演,结果表明本次地震的破裂过程是一个清晰的南东东方向的单侧破裂,破裂尺度约为105km,整体持续时间约为58s.在破裂初始的前15s,能量辐射基本围绕在震源附近,16s后破裂开始向南东东方向以1.9km·s-1的速度破裂.释放能量最大的时间为第38s,位于距震中70km处.该位置从第29秒开始破裂,并持续释放能量长达30s之久.
An MW7.9earthquake occurred in Nepal on 25 April,2015.Its hypocenter is located at28.1°N,84.7°E.In order to investigate the rupturing process of this temblor in detail,we use the multi-array compressive sensing(MCS)method to invert vertical component data of teleseismic P waves recorded by 179 stations of Alaska,Europe and Australia arrays.Traditionally,the compressive sensing(CS)method,based on data from unique array,can recover sparsely distributed source locations in the frequency domain.While the MCS could improve the resolution because of the larger azimuth coverage range than only using data from single array.To apply this method,the first thing is to align the data from each array using cross-correlation respectively.Secondly we stack the aligned data from each array to make the first P wave pulse clear enough to be recognized so that all the data could be aligned.Finally we invert the spatiotemporal rupture process with a sliding window based on the multi-array compressive sensing method.Combining with the discriminant factor(DF),we reduce artifactsand obtain a more credible result.The result indicates that there is a unilateral rupture with orientation of SEE,length of 105 km,and duration time of 58 s.During the first 15 sof failure,the power radiation is mainly distributed around the epicenter.Since 16 s,the rupture propagated toward SEE with a rate of1.9km·s-1.The largest energy is released at 38 s,70km from the hypocenter.The break of this position starts from 29 sand lasts for 30 s.Additionally,we compare the rupture details of the Nepal earthquake and 2008 Wenchuan earthquake because of their same magnitude.Moreover,MCS can offer zones where power radiated intensely, which could provide helpful information for emergency rescue after earthquakes.And we discuss the improvement of resolution because of the larger azimuth coverage range.In the end,based on slip deficit and rate of accumulation of moment deficit,we conclude that this 2015 earthquake could be a repeat of the 1833 M7.7 Nepal temblor.And the possibility of the occurrence of a larger earthquake in this region cannot be excluded.
An MW7.9earthquake occurred in Nepal on 25 April,2015.Its hypocenter is located at28.1°N,84.7°E.In order to investigate the rupturing process of this temblor in detail,we use the multi-array compressive sensing(MCS)method to invert vertical component data of teleseismic P waves recorded by 179 stations of Alaska,Europe and Australia arrays.Traditionally,the compressive sensing(CS)method,based on data from unique array,can recover sparsely distributed source locations in the frequency domain.While the MCS could improve the resolution because of the larger azimuth coverage range than only using data from single array.To apply this method,the first thing is to align the data from each array using cross-correlation respectively.Secondly we stack the aligned data from each array to make the first P wave pulse clear enough to be recognized so that all the data could be aligned.Finally we invert the spatiotemporal rupture process with a sliding window based on the multi-array compressive sensing method.Combining with the discriminant factor(DF),we reduce artifactsand obtain a more credible result.The result indicates that there is a unilateral rupture with orientation of SEE,length of 105 km,and duration time of 58 s.During the first 15 sof failure,the power radiation is mainly distributed around the epicenter.Since 16 s,the rupture propagated toward SEE with a rate of1.9km·s-1.The largest energy is released at 38 s,70km from the hypocenter.The break of this position starts from 29 sand lasts for 30 s.Additionally,we compare the rupture details of the Nepal earthquake and 2008 Wenchuan earthquake because of their same magnitude.Moreover,MCS can offer zones where power radiated intensely, which could provide helpful information for emergency rescue after earthquakes.And we discuss the improvement of resolution because of the larger azimuth coverage range.In the end,based on slip deficit and rate of accumulation of moment deficit,we conclude that this 2015 earthquake could be a repeat of the 1833 M7.7 Nepal temblor.And the possibility of the occurrence of a larger earthquake in this region cannot be excluded.
引文
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Candès E J,Romberg J,Tao T.2006.Robust uncertaintyprinciples:Exact signal reconstruction from highly incompletefrequency information.IEEE Transactions on InformationTheory,52(2):489-509.
Donoho D L.2006.Compressed sensing.IEEE Transactions onInformation Theory,52(4):1289-1306.
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Lustig M,Donoho D,Pauly J M.2007.Sparse MRI:Theapplication of compressed sensing for rapid MR imaging.Magnetic Resonance in Medicine,58(6):1182-1195.
Malioutov D,etin M,Willsky A S.2005.A sparse signalreconstruction perspective for source localization with sensorarrays.IEEE Transactions on Signal Processing,53(8):3010-3022.
Meng L S,Inbal A,Ampuero J P.2011.A window into thecomplexity of the dynamic rupture of the 2011 Mw9 TohokuOki earthquake.Geophysical Research Letters,38(7):L00G07.
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Sapkota S N,Bollinger L,Klinger Y,et al.2013.Primary surfaceruptures of the great Himalayan earthquakes in 1934and 1255.Nature Geoscience,6(1):71-76.
Schmidt R O.1986.Multiple emitter location and signal parameterestimation.IEEE Transactions on Antennas and Propagation,34(3):276-280.
Wang W M,Zhao L F,Li J,et al.2008.Rupture process of theMS8.0 Wenchuan earthquake of Sichuan,China.Chinese J.Geophys.(in Chinese),51(5):1403-1410,doi:10.3321/j.issn:0001-5733.2008.05.013.
Xu Y,Koper K D,Sufri O,et al.2009.Rupture imaging of theMw7.9 12May 2008Wenchuan earthquake from back projection ofteleseismic P waves.Geochemistry,Geophysics,Geosystems,10(4):Q04006.
Yao H J,Gerstoft P,Shearer P M,et al.2011.Compressivesensing of the Tohoku-Oki Mw9.0 earthquake:Frequencydependent rupture modes.Geophysical Research Letters,38(20):L20310.
Zhang H,Ge Z X.2010.Tracking the rupture of the 2008Wenchuan earthquake by using the relative back-projectionmethod.Bulletin of the Seismological Society of America,100(5B):2551-2560.
Zhang Y,Feng W P,Xu L S,et al.2009.Spatiotemporal ruptureprocess of the 2008 Wenchuan great earthquake.Science inChina(Series D:Earth Sciences),52(2):145-154.
Zhang Y,Wang R J,Zschau J,et al.2014.Automatic imaging ofearthquake rupture processes by iterative deconvolution andstacking of high-rate GPS and strong motion seismograms.Journal of Geophysical Research:Solid Earth,119(7):5633-5650.
王卫民,赵连锋,李娟等.2008.四川汶川8.0级地震震源过程.地球物理学报,51(5):1403-1410,doi:10.3321/j.issn:0001-5733.2008.05.013.
张勇,冯万鹏,许力生等.2008.年汶川大地震的时空破裂过程.中国科学(D辑),38(10):1186-1194.
Aki K,Richards P G.2002.Quantitative Seismology(Vol.1):Theory and Methods.Sansalito,CA:University Science Books.
Ambraseys N N,Douglas J.2004.Magnitude calibration of northIndian earthquakes.Geophysical Journal International,159(1):165-206.
Bilham R,Ambraseys N.2005.Apparent Himalayan slip deficitfrom the summation of seismic moments for Himalayanearthquakes,1500-2000.Current Science,88(10):1658-1663.
Bollinger L,Sapkota S N,Tapponnier P,et al.2014.Estimatingthe return times of great Himalayan earthquakes in easternNepal:Evidence from the Patu and Bardibas strands of theMain Frontal Thrust.Journal of Geophysical Research:SolidEarth,119(9):7123-7163.
Candès E J,Romberg J,Tao T.2006.Robust uncertaintyprinciples:Exact signal reconstruction from highly incompletefrequency information.IEEE Transactions on InformationTheory,52(2):489-509.
Donoho D L.2006.Compressed sensing.IEEE Transactions onInformation Theory,52(4):1289-1306.
Duarte M F,Davenport M A,Takhar D,et al.2008.Single-pixelimaging via compressive sampling.IEEE Signal ProcessingMagazine,25(2):83-91.
Dziewonski A M,Anderson D L.1981.Preliminary reference Earthmodel.Physics of the Earth and Planetary Interiors,25(4):297-356.
Goldstein P,Archuleta R J.1991.Deterministic frequencywavenumber methods and direct measurements of rupturepropagation during earthquakes using a dense array:Theoryand methods.Journal of Geophysical Research:Solid Earth(1978—2012),96(B4):6173-6185.
Hough S E,Roger B.2008.Site response of the Ganges basininferred from re-evaluated macroseismic observations from the1897Shillong,1905 Kangra,and 1934 Nepal earthquakes.Journal of Earth System Science,117(2S):773-782.
Ishii M,Shearer P M,Houston H,et al.2005.Extent,durationand speed of the 2004Sumatra—Andaman earthquake imagedby the Hi-Net array.Nature,435(7044):933-936.
Koper K D,Hutko A R,Lay T,et al.2012.Imaging short-periodseismic radiation from the 27 February 2010 Chile(Mw8.8)earthquake by back-projection of P,PP,and PKIKP waves.Journal of Geophysical Research:Solid Earth(1978—2012),117(B2):B02308.
Lustig M,Donoho D,Pauly J M.2007.Sparse MRI:Theapplication of compressed sensing for rapid MR imaging.Magnetic Resonance in Medicine,58(6):1182-1195.
Malioutov D,etin M,Willsky A S.2005.A sparse signalreconstruction perspective for source localization with sensorarrays.IEEE Transactions on Signal Processing,53(8):3010-3022.
Meng L S,Inbal A,Ampuero J P.2011.A window into thecomplexity of the dynamic rupture of the 2011 Mw9 TohokuOki earthquake.Geophysical Research Letters,38(7):L00G07.
Meng L,Ampuero J P,Stock J,et al.2012.Earthquake in a maze:Compressional rupture branching during the 2012 Mw8.6Sumatra earthquake.Science,337(6095):724-726.
Rost S,Thomas C.2002.Array seismology:methods and applications.Reviews of Geophysics,40(3):2-1-2-27.
Sapkota S N,Bollinger L,Klinger Y,et al.2013.Primary surfaceruptures of the great Himalayan earthquakes in 1934and 1255.Nature Geoscience,6(1):71-76.
Schmidt R O.1986.Multiple emitter location and signal parameterestimation.IEEE Transactions on Antennas and Propagation,34(3):276-280.
Wang W M,Zhao L F,Li J,et al.2008.Rupture process of theMS8.0 Wenchuan earthquake of Sichuan,China.Chinese J.Geophys.(in Chinese),51(5):1403-1410,doi:10.3321/j.issn:0001-5733.2008.05.013.
Xu Y,Koper K D,Sufri O,et al.2009.Rupture imaging of theMw7.9 12May 2008Wenchuan earthquake from back projection ofteleseismic P waves.Geochemistry,Geophysics,Geosystems,10(4):Q04006.
Yao H J,Gerstoft P,Shearer P M,et al.2011.Compressivesensing of the Tohoku-Oki Mw9.0 earthquake:Frequencydependent rupture modes.Geophysical Research Letters,38(20):L20310.
Zhang H,Ge Z X.2010.Tracking the rupture of the 2008Wenchuan earthquake by using the relative back-projectionmethod.Bulletin of the Seismological Society of America,100(5B):2551-2560.
Zhang Y,Feng W P,Xu L S,et al.2009.Spatiotemporal ruptureprocess of the 2008 Wenchuan great earthquake.Science inChina(Series D:Earth Sciences),52(2):145-154.
Zhang Y,Wang R J,Zschau J,et al.2014.Automatic imaging ofearthquake rupture processes by iterative deconvolution andstacking of high-rate GPS and strong motion seismograms.Journal of Geophysical Research:Solid Earth,119(7):5633-5650.
王卫民,赵连锋,李娟等.2008.四川汶川8.0级地震震源过程.地球物理学报,51(5):1403-1410,doi:10.3321/j.issn:0001-5733.2008.05.013.
张勇,冯万鹏,许力生等.2008.年汶川大地震的时空破裂过程.中国科学(D辑),38(10):1186-1194.
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