2012年4月11日苏门答腊8.6级地震前后川滇地区波速变化研究
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摘要
利用2012年1～6月川滇地区(21°～34°N,97°～108°E)99个测震数字地震台的连续波形资料,采用背景噪声层析成像方法反演了2012年4月11日苏门答腊8.6级地震前后川滇地区的波速变化,同时研究了该地震前后川滇地区地震活动的变化特征。结果表明,川滇地区波速结构呈现龙门山断裂带南段至元谋—绿汁江断裂带和安宁河断裂带波速降低而两侧波速升高的特点。同时,波速变化与地震活动性变化具有明显的相关性:在宁蒗—木里和乐山—雅安一带波速增高显著,地震活动速率也增加;在龙门山断裂带南段至安宁河断裂带上则表现为明显的波速降低,而安宁河断裂带也是地震活动速率降低区域。这表明本研究得到的波速变化的结果有一定的可信度,也为背景噪声方法应用到地震预测提供了一种可能的途径。
Velocity changes before and after the April 11,2012Sumatra MS 8.6earthquake have been inverted by ambient tomography method,using continuous waveform records of 99stations in Sichuan seismic network and Yunnan seismic network from Jan.,to Jun.,2012.The characteristics of seismicity in the Sichuan—Yunnan region are also analyzed during the earthquake.Results show that the velocity from the southern segment of Longmenshan fault to Yuanmou—lvzhijiang fault zone and Anninghe fault zone decreased,while the velocity of both sides increased.At the same time,wave velocity changes have a significant correlation with the changes of seismicity.The wave velocity increased together with the seismicity rate in Ninglang—Muli and Leshan—Yaan regions.Wave velocity decreased from the southern segment of Longmenshan Fault zone to Anninghe Fault zone.The seismicity rate of Anninghe Fault zone was also decreased.These show that the results of the velocity change are credible to some extent.
Velocity changes before and after the April 11,2012Sumatra MS 8.6earthquake have been inverted by ambient tomography method,using continuous waveform records of 99stations in Sichuan seismic network and Yunnan seismic network from Jan.,to Jun.,2012.The characteristics of seismicity in the Sichuan—Yunnan region are also analyzed during the earthquake.Results show that the velocity from the southern segment of Longmenshan fault to Yuanmou—lvzhijiang fault zone and Anninghe fault zone decreased,while the velocity of both sides increased.At the same time,wave velocity changes have a significant correlation with the changes of seismicity.The wave velocity increased together with the seismicity rate in Ninglang—Muli and Leshan—Yaan regions.Wave velocity decreased from the southern segment of Longmenshan Fault zone to Anninghe Fault zone.The seismicity rate of Anninghe Fault zone was also decreased.These show that the results of the velocity change are credible to some extent.
引文
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[25]易桂喜,闻学泽,张致伟,等.川南马边地区强震危险性分析[J].地震地质,2010,32(2):282-293.
[26]刘平江,刁桂苓,宁杰远.川滇地块的震源机制解特征及其地球动力学解释[J].地震学报,2007,29(5):449-458.
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[2]张国民,张晓东,刘杰,等.印尼苏门答腊8.7级大震对中国陆区的影响[J].地震,2005,25(4):15-25.
[3]杨国华,江在森,王敏,等.印尼地震对我国川滇地区地壳水平活动的影响[J].大地测量与地球动力学,2006,26(1):9-20.
[4]Sabra K G,Gerstoft P,Roux P.Surface wave tomography from microseisms in Southern California[J].Geophys Res Lett,2005,32:L14311.
[5]Brenguier F,Shapiro N M,Campillo M.Towards forecasting volcanic eruptions using seismic noise[J].Nature Geoscience,2008,1:126-130.
[6]Stehly L,Campillo M,Shapiro N M.Traveltime measurements from noise correlation:Stability anddetection of instrumental time-shifts[J].Geophys J Int,2007,171:223-230.
[7]Xu Z J,Song X D.Temporal changes of surface wave velocity associated with major Sumatra earth-quakes from ambient noise correlation[J].PNAS,2009,106(34):14207-14212.
[8]Wegler U,Sens-Schonfelder C.Fault zone monitoring with passive image interferometry[J].Geo-phys J Int,2007,168(3):1 029-1 033.
[9]Cheng X,Niu F,Wang B S.Coseismic Velocity Change in the Rupture Zone of the 2008 MW7.9Wenchuan Earthquake Observed from Ambient Seismic Noise[J].BSSA,2010,100(5):2 539-2 550.
[10]刘志坤,黄金莉.利用背景噪声互相关研究汶川地震震源区地震波速度变化[J].地球物理学报,2010,53(4):853-863.
[11]杨润海,王彬,郑定昌,等.云南地区波速变化与强震孕育[J].地震研究,2011,34(4):420-427.
[12]赵盼盼,陈九辉,刘启元,等.汶川地震区地壳速度相对变化的环境噪声自相关研究[J].地球物理学报,2012,55(1):137-145.
[13]Weaver R L.Information from seismic noise[J].Science,2005,307:1 568-1 569.
[14]Bensen G D,Ritzewoller M H,Barmin M P,et al.Processing seismic ambient noise data to obtainreliable broad-band surface wave dispersion measurements[J].Geophys J Int,2007,169(3):1 239-1260.
[15]杨文,刘杰,史海霞,等.用噪声成像方法研究云南地区强震前地震面波速度变化[J].地震,2011,31(3):103-111.
[16]Schaff D P,Beroza G C.Coseismic and postseismic velocity changes measured by repeating earth-quakes[J].Journal of Geophysical Research,2004,109:B10302.
[17]Waldhauser F,Lippitsch R,KisslingE,et al.High-resolution teleseismic tomography of upper-mantle structure using an priori three-dimensional crustal model[J].Geophys J Int,2002,150:403-414.
[18]周龙泉,刘杰,苏有锦,等.利用S波高频衰减参数对云南地区地壳Q值成像[J].地球物理学报,2009,52(6):1 500-1 507.
[19]刘福田,李强,吴华,等.用于速度图象重建的层析成象法[J].地球物理学报,1989,32(1):46-61.
[20]熊绍柏,滕吉文,尹周勋,等.攀西构造带南部地壳与上地幔结构的爆炸地震研究[J].地球物理学报,1986,29(3):235-244.
[21]白志明,王椿镛.云南地区上部地壳结构和地震构造环境的层析成像研究[J].地震学报,2003,25(2):117-126.
[22]中国地震局监测预报司.中国大陆地震序列研究[M].北京:地震出版社,2007.
[23]Fred F,Ross S,Volkan S,et al.The 11April 2012east Indian Ocean earthquaketriggered large af-tershocks worldwide[J].Nature,2012,490:249-255.
[24]程万正,刁桂苓,吕弋培,等.川滇地块的震源力学机制、运动速率和活动方式[J].地震地质,2003,25(1):71-87.
[25]易桂喜,闻学泽,张致伟,等.川南马边地区强震危险性分析[J].地震地质,2010,32(2):282-293.
[26]刘平江,刁桂苓,宁杰远.川滇地块的震源机制解特征及其地球动力学解释[J].地震学报,2007,29(5):449-458.
[27]Julian B R,Foulger G R.Time-dependent seismic tomography[J].Geophys J Int,2010,182:1 327-1 338.
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