鲜水河断裂带跨断层变形分析和数值模拟
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摘要
鲜水河断裂带积累了20多年的跨断层变形资料,如何解释这种变形是一个重要的问题。该文采用了弹性上地壳覆盖在粘弹性Max well体之上的模型。炉霍1973年MS7.6地震按该粘弹性模型计算的震后形变曲线能够在很大程度上解释实测观测结果,显示与一些断层(如圣安德烈斯断层某些段落)存在缓慢蠕滑而无大地震发生不同,鲜水河断裂带观测到的跨断层变形,有相当一部分可以用大地震后的粘弹性变形来解释。当然,计算得到的震后粘弹性形变幅度同跨断层短基线和短水准的实测形变幅度比较还存在一些差异,不能完全解释,表明了大陆断层活动的复杂性,并值得进一步深入研究。
Data of cross-over fault deformation for more than 20 years have been accumulated along the Xianshuihe fracture zone. It is an important problem of how to explain this kind of deformation. This paper adopted the viscoelastic model to study this problem, the lower crust is assumed Maxwell rheology covered by an elastic upper crust. The post-seismic deformation of the MS7.6 Luhuo earthquake in 1973 computed by this model can explain the observation data to a great degree, showing that Xianshuihe fault is different from some faults (such as some of segments in San Andres Fault), which creeps slowly and there is no large earthquake occurred on it. And a significant part of the cross-over deformation observed along Xianshuihe fracture zone can be explained by post-seismic viscoelastic deformation after large earthquakes. However, this kind of model can not explain the entire deformation. Deviation exists between viscoelastic model and the actual observation of cross-over fault short baseline and short water level. It indicates that the activity of continental faults is complicated and it is worth to further studies.
Data of cross-over fault deformation for more than 20 years have been accumulated along the Xianshuihe fracture zone. It is an important problem of how to explain this kind of deformation. This paper adopted the viscoelastic model to study this problem, the lower crust is assumed Maxwell rheology covered by an elastic upper crust. The post-seismic deformation of the MS7.6 Luhuo earthquake in 1973 computed by this model can explain the observation data to a great degree, showing that Xianshuihe fault is different from some faults (such as some of segments in San Andres Fault), which creeps slowly and there is no large earthquake occurred on it. And a significant part of the cross-over deformation observed along Xianshuihe fracture zone can be explained by post-seismic viscoelastic deformation after large earthquakes. However, this kind of model can not explain the entire deformation. Deviation exists between viscoelastic model and the actual observation of cross-over fault short baseline and short water level. It indicates that the activity of continental faults is complicated and it is worth to further studies.
引文
[1]Wang R,Francisco Lorenzo Martin,Frank Roth.PSGRN/PSCMP-a newcode for calculating co-and postseismic deformation,geoid and gravity changes based on the viscoelastic-gravitational dislocation theory[J].Computers&Geosciences,2006,32:527-541.
[2]闻学泽,白兰香.鲜水河断裂带北西段地壳破裂图象及地震构造[A].四川省地震局.鲜水河断裂带地震学术讨论会文集[C].北京:地震出版社,1985.33-40.
[3]闻学泽.四川鲜水河-安宁河-则木河断裂带的地震破裂分段特征[J].地震地质,2000,22(3):239-249.
[4]Zhou H,Liu H,Kanamori H.Source processes of large eartquake along the Xianshuihe Fault in sourthwest China[J].Bull Seismol Soc Amer,1983,73(2):537-551.
[5]林邦慧,陈天长,薄晓红,等.鲜水河断裂带强震的破裂过程与地震活动[J].地震学报,1986,8(1):1-20.
[6]Wen Xue-ze,Yi Gui-xi,Zhang Pei-zhen,et al.Ti me-dependent seismic hazard assessment for the eastern-boundary fault zone of the Sichuan-Yunan Block[M].China,1999,141-154.
[7]王椿镛,Mooney WD,王溪莉,等.川滇地区地壳上地幔三维速度结构研究[J].地震学报,2002,24(1):1-16.
[8]Wang Y.Heat flow pattern and lateral variations of lithoshpere strength in China mainland:con-straints on acitve deformation[J].Physics of the Earth and Planetary Interiors,2001,126:121-146.
[9]陶本藻,杜方.多面函数法研究鲜水河地区现今地壳垂直运动[J].武汉测绘科技大学学报,1991,16(3):12-22.
[10]张国民,李丽.强震成组孕育和发生过程中相互间影响的研究[J].地震,1997,17(3):221-231.
[11]张秋文,张培震,王乘,等.鲜水河断裂带断层间相互作用的触震与缓震效应[J].地震学报,2003,25(2):143-153.
[12]吕弋培,李铁明,廖华.鲜水河断裂带跨断层形变测量及其地震学意义[J].地震地质,1997,19(4):333-341.
[13]吕弋培,廖华.鲜水河断裂形变场、重力场、磁场动态演化特征与地震[J].四川地震,2001,(3):11-17.
[14]Goetz H,Bokel mann R,Robert L.Long-termcreep-rate changes and their causes.Geophysical Re-search Letters[J].2003,30(8):1445,doi:10.1029/2003GL017012.
[2]闻学泽,白兰香.鲜水河断裂带北西段地壳破裂图象及地震构造[A].四川省地震局.鲜水河断裂带地震学术讨论会文集[C].北京:地震出版社,1985.33-40.
[3]闻学泽.四川鲜水河-安宁河-则木河断裂带的地震破裂分段特征[J].地震地质,2000,22(3):239-249.
[4]Zhou H,Liu H,Kanamori H.Source processes of large eartquake along the Xianshuihe Fault in sourthwest China[J].Bull Seismol Soc Amer,1983,73(2):537-551.
[5]林邦慧,陈天长,薄晓红,等.鲜水河断裂带强震的破裂过程与地震活动[J].地震学报,1986,8(1):1-20.
[6]Wen Xue-ze,Yi Gui-xi,Zhang Pei-zhen,et al.Ti me-dependent seismic hazard assessment for the eastern-boundary fault zone of the Sichuan-Yunan Block[M].China,1999,141-154.
[7]王椿镛,Mooney WD,王溪莉,等.川滇地区地壳上地幔三维速度结构研究[J].地震学报,2002,24(1):1-16.
[8]Wang Y.Heat flow pattern and lateral variations of lithoshpere strength in China mainland:con-straints on acitve deformation[J].Physics of the Earth and Planetary Interiors,2001,126:121-146.
[9]陶本藻,杜方.多面函数法研究鲜水河地区现今地壳垂直运动[J].武汉测绘科技大学学报,1991,16(3):12-22.
[10]张国民,李丽.强震成组孕育和发生过程中相互间影响的研究[J].地震,1997,17(3):221-231.
[11]张秋文,张培震,王乘,等.鲜水河断裂带断层间相互作用的触震与缓震效应[J].地震学报,2003,25(2):143-153.
[12]吕弋培,李铁明,廖华.鲜水河断裂带跨断层形变测量及其地震学意义[J].地震地质,1997,19(4):333-341.
[13]吕弋培,廖华.鲜水河断裂形变场、重力场、磁场动态演化特征与地震[J].四川地震,2001,(3):11-17.
[14]Goetz H,Bokel mann R,Robert L.Long-termcreep-rate changes and their causes.Geophysical Re-search Letters[J].2003,30(8):1445,doi:10.1029/2003GL017012.
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