汶川地震前南北地震带中北段地形变变化特征的研究
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摘要
2008年5月12日汶川8.0级地震是我国自建国以来灾难最为严重的一次强地震。文中讨论了汶川地震前震源附近与外围地区潮汐形变变化及龙门山地震带、鲜水河地震带和祁连山地震带断层活动的特点。分析结果表明:震前沿龙门山地震带分布的雅安、汶川及茂县观测台地倾斜测项在2006年初发生转折,由单向东倾或西倾转向平稳,临震前无明显变化;龙门山断裂带及附近地区有5个断层水准观测场地,除耿达场地观测到巨幅变化外,其他场地震前未观测到突出的前兆性变化。震源外围龙灯坝断层蠕变仪(Δ=220 km)震前观测到持续时间在3个月左右的突变性异常,但依据突变持续时间较难估计相应地震为8级。而离震中较远的祁连山地震带中西段,震前也有巨大的断层水准变化,其与汶川地震的关系值得讨论。
This paper analyzes the characteristics of observed ground tilts and strains near and around the Wenchuan earthquake rupture zone,and of the measured changes of Longmenshan,Xianshuihe and Qilian seismic belts.The observed phenomenon demonstrated that the ground tilt velocities at Ya'an,Wenchuan and Maoxian sites turned abruptely in the beginning of 2006,and then decreased steadily up to the occurrence of Wenchuan earthquake.The five sites for cross fault measurement on the Longmenshan seismic belt,the great change was only observed on Gengda site,but the change maybe caused mainly by the new buildings near the site.A rapid change durated for three months was observed by the fault creep-meter at the Longdengba site 220 km away from the epicenter,which gives us information for an M6.5 earthquake in three to four months after the rapid change ended.Great changes were also observed using fault leveling on the Qilian seismic belt,the question if they were related to the Wenchuan earthquake is to be studied.
This paper analyzes the characteristics of observed ground tilts and strains near and around the Wenchuan earthquake rupture zone,and of the measured changes of Longmenshan,Xianshuihe and Qilian seismic belts.The observed phenomenon demonstrated that the ground tilt velocities at Ya'an,Wenchuan and Maoxian sites turned abruptely in the beginning of 2006,and then decreased steadily up to the occurrence of Wenchuan earthquake.The five sites for cross fault measurement on the Longmenshan seismic belt,the great change was only observed on Gengda site,but the change maybe caused mainly by the new buildings near the site.A rapid change durated for three months was observed by the fault creep-meter at the Longdengba site 220 km away from the epicenter,which gives us information for an M6.5 earthquake in three to four months after the rapid change ended.Great changes were also observed using fault leveling on the Qilian seismic belt,the question if they were related to the Wenchuan earthquake is to be studied.
引文
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[15]Roger Bilham.Co-seismic strain and the Transition to Surface Afterslip recorded by Creep-metersnear the 2004 Parkfield epicenter[J].Seism Res Lett Jan,2005,76(1):49-57.
[2]王时标,王光远.多闭锁点地区地震预测唯象模型[J].地球物理学进展,1999,14(2):7-26.
[3]牛安福.突变性及与地震关系的研究[J].地震学报,2003,25(4):441-445.
[4]牛安福.丽江地震前后西南地区定点形变变化的特点分析[J].内陆地震,2004,18(4):300-305.
[5]牛安福,张晶,张晓青,等.昆仑山口西8.1级地震前祁连山地震带附近形变异常的演化特征[J].地震,2003,23(4):21-26.
[6]刘耀炜,牛安福,卢军.强地震短期前兆异常的物理解释[M].北京:地震出版社,2005.
[7]Kanamori H,Stewart G S.A slow earthquake[J].Phys Earth Planet Inter,1979,18:167-175.
[8]Linde A T,Gladwin M T,Johnston M J.A slow earthquake sequence on the San Andreas fault[J].Nature,1996,383:65-68.
[9]Linde A T,Sacks I S.Slow earthquakes and great earthquakes along the Nankai trough[J].Earthand Planetary Science Letters,2002,203(1):265-275.
[10]牛安福,张晶,高福旺,等.形及与地震关系的研究[J].大地测量与地球动力学,2002,1(1):29-33.
[11]牛安福.地壳形变观测与地震前兆一般性问题的讨论[J].国际地震动态,2007,(6):43-48.
[12]牛安福,吉平,闫伟,等.中国大陆6级地震平静后首次强地震的短期预测实验[J].中国地震,24(1):61-66.
[13]车兆宏,刘向军.用流动形变观测判定强震危险地点的研究[J].地壳形变与地震,2000,16(1):46-51.
[14]吴云.台湾集集921地震地壳形变的简介与讨论[J].地壳形变与地震,2001,21(2):59-63.
[15]Roger Bilham.Co-seismic strain and the Transition to Surface Afterslip recorded by Creep-metersnear the 2004 Parkfield epicenter[J].Seism Res Lett Jan,2005,76(1):49-57.
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