汶川Ms8.0地震同震倾斜应变变化分析
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摘要
对汶川地震震中附近450 km范围内倾斜仪、应变仪记录到的同震变化做了筛选统计,并根据弹性半无限空间矩形位错模型,分别采用远场地震波资料、近场大地测量资料反演的同震滑移分布模型,正演计算震中附近台站的同震倾斜、应变变化。通过对实际观测与模拟计算结果的比较,初步表明:实际观测的同震倾斜变化方向与模拟计算结果存在75%的一致性,实际观测的同震倾斜变化比模拟值大约1～2个量级;实际观测的同震应变方向与模拟计算结果仅有33.3%的一致性,实际观测的同震应变变化与模拟计算值相当或仅大1个数量级。
Coseismic tilt and strain offsets for Wenchuan Ms8.0 earthquake had been recorded by almost all of the continuous tilt and strain instruments in China.These offsets can be interpreted as qui-static tectonic changes after the earthquake.We calculate coseismic tit and strain offsets at the stations around about 450 km of the epicenter and coseismic tilt and strain offsets are simulated with half-space elastic dislocation model,particalarly using finite slip models inversed from far-field broadband seismic waveforms and from near-field geodetic data(GPS&InSAR).Consequently,comparisons between the observed and modeled offsets for tilt-and strain-meters are analyzed.Our preliminary study demonstrates that the directions of observed ～75% tilt offset and ～33.3% strain offset are consistent with that modeled,respectively,and the magnitude of the observed tilt offsets are 1-2 orders larger than that of modeled,whereas the observed strain offsets are coherent with the modeled or 1 orders of magnitude larger than that of modeled.
Coseismic tilt and strain offsets for Wenchuan Ms8.0 earthquake had been recorded by almost all of the continuous tilt and strain instruments in China.These offsets can be interpreted as qui-static tectonic changes after the earthquake.We calculate coseismic tit and strain offsets at the stations around about 450 km of the epicenter and coseismic tilt and strain offsets are simulated with half-space elastic dislocation model,particalarly using finite slip models inversed from far-field broadband seismic waveforms and from near-field geodetic data(GPS&InSAR).Consequently,comparisons between the observed and modeled offsets for tilt-and strain-meters are analyzed.Our preliminary study demonstrates that the directions of observed ～75% tilt offset and ～33.3% strain offset are consistent with that modeled,respectively,and the magnitude of the observed tilt offsets are 1-2 orders larger than that of modeled,whereas the observed strain offsets are coherent with the modeled or 1 orders of magnitude larger than that of modeled.
引文
1 Agnew D C.Before PBO:An overview of continuous strainand tilt measurements in the United States[J].Journal of theGeodetic Society of Japan,2007,53:157-182.
2 Wyatt F,Cabaniss G and AgnewD C.A comparison of tilt-meters at tidal frequencies[J].Geophys.Res.Lett.,1982,9:743-746.
3 Press F.Displacements,strains,and tilts at teleseismic dis-tances[J],J.Geophys.Res.,1965,70:2 395-2 412.
4 McHuge S,Johnston M J S.An analysis of coseismic tiltchanges from an array in central California[J].J.Geophys.Res.,1977,82:5 692-5 698.
5周克昌,吴翼麟.由同震倾斜阶跃应用反演方法研究震源机制[J].地壳形变与地震,1990,(1):13-20.(ZhouKechang,Wu Yilin,Source mechanism study by inversion ofcoseismic tilt steps[J].Crustal Deformation and Earth-quake,1990,(1):13-20)
6许才军,刘洋,温扬茂.利用GPS资料反演汶川Mw7.9级地震滑移分布[J].测绘学报,2009,38(3):195-215.(Xu Caijun,Liu Yang and Wen Yangmao.Mw7.9 Wen-chuan earthquake slip distribution inversion from GPS meas-urements[J].Acta Geodaetica et Cartographic Sinica,2009,38(3):195-215)
7 Shen Z K,Sun J B,Zhang Peizhen,et.al.Slip maxima atfault junction and rupturing of barriers during the 2008 Wen-chuan earthquake[J].Nature Geoscience,2009,20(10):718-724.
8 Okada Y.Surface deformation due to shear and tensile faultsin a half-space[J].Bull.Seism.Soc.Am.,1985,75:1 135-1 154
9 Okada Y.Internal deformation due to shear and tensile faultsin a half-space[J].Bull.Seism.Soc.Am.,1992,82(2):1 018-1 040.
10 http://earthquake.usgs.gov/eqcenter/eqinthenews/2008/us2008ryan/finite_fault.php
11孙文科,地震火山活动产生重力变化的理论与观测研究的进展及现状[J].大地测量与地球动力学,2008,(4):44-53.(Sun Wenke.Progess and current situation of re-search on theory and observation of gravity chance causedby seismicity and volcanism[J].Journal of Geodesy andGeodynamics,2008,(4):44-53)
12 Roger D.Borcherdt et al.Recording of the 2004 ParkfieldEarthquake on the General Earthquake Observation SystemArray:Implications for Earthquake Precursors,Fault Rup-ture and Coseismic strain Changes[J],Bull.Seism.Soc.Am.,2006,96:S73-S89.
13 Harrison J C.Cavity and topographic effects in tilt andstrain measurement[J].J.Geophys.Res.,1976,81:319-328.
14刘启元,等.汶川Ms8.0地震:川西流动地震台阵观测数据的初步分析[J].地震地质,2008,30(3):584-596.(Liu Qiyuan,et al.TheMs8.0 wenchuan earthquake:pre-liminary results from the western Sichuan mobile seismic ar-ray observations[J].Seismology and Geology,2008,30(3):584-596)
15 Borcherdt R D,Johnston MJ S and Glassmoyer G.On theuse of volumetric strain meters to infer additional character-istics of short-period seismic radiation[J],Bull.Seism.Soc.Am.,1989,79(4):1 006-1 023.
16刘序俨,洪星.潮汐倾斜的几何物理含义与其剪应变属性[J].大地测量与地球动力学,2007,(4):82-86.(Liu Xuyan and Hong Xing.Geometric and physical mean-ing of tidal tilt and it’s shear strain property[J].Journal ofGeodesy and Geodynamics,2007,(4):82-86)
2 Wyatt F,Cabaniss G and AgnewD C.A comparison of tilt-meters at tidal frequencies[J].Geophys.Res.Lett.,1982,9:743-746.
3 Press F.Displacements,strains,and tilts at teleseismic dis-tances[J],J.Geophys.Res.,1965,70:2 395-2 412.
4 McHuge S,Johnston M J S.An analysis of coseismic tiltchanges from an array in central California[J].J.Geophys.Res.,1977,82:5 692-5 698.
5周克昌,吴翼麟.由同震倾斜阶跃应用反演方法研究震源机制[J].地壳形变与地震,1990,(1):13-20.(ZhouKechang,Wu Yilin,Source mechanism study by inversion ofcoseismic tilt steps[J].Crustal Deformation and Earth-quake,1990,(1):13-20)
6许才军,刘洋,温扬茂.利用GPS资料反演汶川Mw7.9级地震滑移分布[J].测绘学报,2009,38(3):195-215.(Xu Caijun,Liu Yang and Wen Yangmao.Mw7.9 Wen-chuan earthquake slip distribution inversion from GPS meas-urements[J].Acta Geodaetica et Cartographic Sinica,2009,38(3):195-215)
7 Shen Z K,Sun J B,Zhang Peizhen,et.al.Slip maxima atfault junction and rupturing of barriers during the 2008 Wen-chuan earthquake[J].Nature Geoscience,2009,20(10):718-724.
8 Okada Y.Surface deformation due to shear and tensile faultsin a half-space[J].Bull.Seism.Soc.Am.,1985,75:1 135-1 154
9 Okada Y.Internal deformation due to shear and tensile faultsin a half-space[J].Bull.Seism.Soc.Am.,1992,82(2):1 018-1 040.
10 http://earthquake.usgs.gov/eqcenter/eqinthenews/2008/us2008ryan/finite_fault.php
11孙文科,地震火山活动产生重力变化的理论与观测研究的进展及现状[J].大地测量与地球动力学,2008,(4):44-53.(Sun Wenke.Progess and current situation of re-search on theory and observation of gravity chance causedby seismicity and volcanism[J].Journal of Geodesy andGeodynamics,2008,(4):44-53)
12 Roger D.Borcherdt et al.Recording of the 2004 ParkfieldEarthquake on the General Earthquake Observation SystemArray:Implications for Earthquake Precursors,Fault Rup-ture and Coseismic strain Changes[J],Bull.Seism.Soc.Am.,2006,96:S73-S89.
13 Harrison J C.Cavity and topographic effects in tilt andstrain measurement[J].J.Geophys.Res.,1976,81:319-328.
14刘启元,等.汶川Ms8.0地震:川西流动地震台阵观测数据的初步分析[J].地震地质,2008,30(3):584-596.(Liu Qiyuan,et al.TheMs8.0 wenchuan earthquake:pre-liminary results from the western Sichuan mobile seismic ar-ray observations[J].Seismology and Geology,2008,30(3):584-596)
15 Borcherdt R D,Johnston MJ S and Glassmoyer G.On theuse of volumetric strain meters to infer additional character-istics of short-period seismic radiation[J],Bull.Seism.Soc.Am.,1989,79(4):1 006-1 023.
16刘序俨,洪星.潮汐倾斜的几何物理含义与其剪应变属性[J].大地测量与地球动力学,2007,(4):82-86.(Liu Xuyan and Hong Xing.Geometric and physical mean-ing of tidal tilt and it’s shear strain property[J].Journal ofGeodesy and Geodynamics,2007,(4):82-86)
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