台湾集集7.6级地震前后福建沿海地区的地壳运动
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摘要
对福建GPS网的5期观测数据(1995、1997、1999、2001、2003)进行了统一处理,得到4个时段(1995~1997、1997~1999、1999~2001、2001~2003)ITRF2000的站速度、福建地区的整体旋转参数和主应变参数。福建地区存在一致的南东向运动地震前(第1时段)运动速度平均为32.1mm/a;震时和震后两年时间内(第2时段)运动速度大幅度增加到38.7mm/a;震后第2个两年(第3时段)运动速度相对于第2时段大幅度减小为30.0mm/a;震后第3个两年(第4时段),运动速率相对第3时段有较大增加并超过了第1时段。福建地区的主应变场,在震前主压应变率(12.4×10-9/a)大于主张应变率(7.1×10-9/a),地壳表现为弹性压缩,主压应变轴为N70.9°W;震后应变场发生了相反的变化,主压应变轴变成了主张应变轴,主张应变率(28.9×10-9/a)大大超过主压应变率(3.7×10-9/a),地壳表现为南东方向弹性伸展,第3时段与第4时段主压应变率逐渐增加,主压应变轴也逐渐恢复到震前的方向。福建地区从1995年到2003年地壳运动速度场与应变场随时间的变化过程,反映了集集大地震发生前后区域应力场加强、弹性应变能积累,震时和震后弹性应变能快速释放与逐渐调整恢复的过程。
After having uniformly processed observed data in the 5 period(1995, 1997, 1999, 2001 and 2003) ,the site velocities of ITRF2000 in 4 time interval (1995-1997, 1997-1999, 2000-2001, 2001-2003),the integral rotation parameters and principal strain parameters in Fujian region are obtained. Fujian region exhibits a consistent southeastward movement: the average velocity before the earthquake (the first time interval) was 32.1 mm/a; the velocity during the earthquake and in the two years after the earthquake (the second time interval) increased greatly to 38.7mm/a; in the second two years after the earthquake (the third time interval) it decreased rapidly,as compared to the second time interval to 30.0 mm/a ; in the third two years after the earthquake(the forth time interval) it increased greatly, as compared with the third time interval, and surpassed that in the first time interval. As regards the principal strain field in Fujian region, the principal compressive strain rate {(12.4}×10+{-9}/a) was larger than the principal tensile strain rate (7.1×10+{-9}/a) before the earthquake and the crust displayed elastic compression with a principal compressive strain axis of N70.9°W. After the earthquake, the strain field turned to the opposite and the principal compressive strain axis changed to the principal tensile strain axis. As a result, the principal tensile strain rate (28.9×10+{-9}/a) was much larger than the principal compressive strain rate (3.7×10+{-9}/a) and the crust exhibited southeastward elastic extension. In the third and forth time interval, the principal compressive strain rates increased gradually and the principal compressive strain axis recovered gradually to the direction as before the earthquake. The variations of crustal motion velocity field and strain field with time in the period from 1995 to 2003 in Fujian region reflected the process of regional stress field strengthening, elastic strain energy accumulation, coseismic rapid release of elastic strain energy, and post-seismic gradual adjustment and recovery before and after the Chi-Chi great earthquake.
After having uniformly processed observed data in the 5 period(1995, 1997, 1999, 2001 and 2003) ,the site velocities of ITRF2000 in 4 time interval (1995-1997, 1997-1999, 2000-2001, 2001-2003),the integral rotation parameters and principal strain parameters in Fujian region are obtained. Fujian region exhibits a consistent southeastward movement: the average velocity before the earthquake (the first time interval) was 32.1 mm/a; the velocity during the earthquake and in the two years after the earthquake (the second time interval) increased greatly to 38.7mm/a; in the second two years after the earthquake (the third time interval) it decreased rapidly,as compared to the second time interval to 30.0 mm/a ; in the third two years after the earthquake(the forth time interval) it increased greatly, as compared with the third time interval, and surpassed that in the first time interval. As regards the principal strain field in Fujian region, the principal compressive strain rate {(12.4}×10+{-9}/a) was larger than the principal tensile strain rate (7.1×10+{-9}/a) before the earthquake and the crust displayed elastic compression with a principal compressive strain axis of N70.9°W. After the earthquake, the strain field turned to the opposite and the principal compressive strain axis changed to the principal tensile strain axis. As a result, the principal tensile strain rate (28.9×10+{-9}/a) was much larger than the principal compressive strain rate (3.7×10+{-9}/a) and the crust exhibited southeastward elastic extension. In the third and forth time interval, the principal compressive strain rates increased gradually and the principal compressive strain axis recovered gradually to the direction as before the earthquake. The variations of crustal motion velocity field and strain field with time in the period from 1995 to 2003 in Fujian region reflected the process of regional stress field strengthening, elastic strain energy accumulation, coseismic rapid release of elastic strain energy, and post-seismic gradual adjustment and recovery before and after the Chi-Chi great earthquake.
引文
[1]引自国家数字地震台网分析中心网站,http//www.eq-igp.ac.cn,Harvard大学震源机制解
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6 Xu Lisheng,G.Patau and Chen Yuntai.Source time functions of the1999,Jiji(Chi-chi)earthquake from GDSNlong pe-riod waveform data using aftershocks as empirical Green’s function[J].Acta Seismologica Sinica,2002,24(2):113-125.(in Chinese)
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7 Li Yanxing,Huang Cheng,Hu Xinkang,et al.The rigid and elastic-plastic model of the blocks in intro-plate and strain status of principal blocks in the continent of China[J].Acta Seismologica Sinica,2001,23(6):565-572.(in Chinese)
8 李延兴,胡新康,李智,等.台海地区的地壳运动与变形[J].地震学报,2002,24(5):487~495.
8 Li Yanxing,Hu Xinkang,Li Zhi,et al.Crustal movement and deformation in Taiwan and its coastal area[J].Acta Seismologica Sinica,2002,24(5):487-495.(in Chi-nese)
1 马杏垣.中国岩石圈动力学地图集[M].北京:中国地图出版社,1989.
1 Ma Xingyuan.Lithospheric dynamic atlas of China[M].Bei-jing:Cartographic Publishing House of China,1989(in Chi-nese)
2 史粦华.福建及邻区现今地壳运动与形变[J].大地测量与地球动力学,2005,25(3):69~74.
2 Shi Linhua.Present-day crustal movement and deformation in Fujian province and adjacent area[J].Journal of Geodesy and Geodynamics,2005,25(3):69-74.(in Chinese)
3 丁国瑜,蔡文伯,于品清,等.中国岩石圈动力学概论[M].北京:地震出版社,1991.
3 Ding Guoyu,et al.An introduction of lithospheric dynamics in China[M].Beijing:Seismological Press,1991.(in Chi-nese)
4 许绍燮.17世纪初泉州-琼山大震组群发生的相关性与构造特征[J].大地测量与地球动力学,2005,25(1):1~5.
4 Xu Shaoxie.Correlation and tectonic characteristics of great earthquake group in Quanzhou-Qiongshan at begining of sev-enteenth century[J].Journal of Geodesy and Geodynamics,2005,25(1):1-5.(in Chinese)
5 王敏,沈正康,牛之俊,等.现今中国大陆地壳运动与活动块体模型[J].中国科学(D辑),2003,33(增刊):21~32.
5 Wang Min,Shen Zhengkang Niu Zhijun,et al.Contemporary crustal deformation of the Chinese continent and tectonic block model[J].Science in China(Series D),2003,46(Supp.)25~40.(in Chinese)
6 许力生,G Patau,陈运泰.用余震作为经验格林函数从GDSN长周期波形资料中提取1999年集集地震的震源时间函数[J].地震学报,2002,24(2):113~125.
6 Xu Lisheng,G.Patau and Chen Yuntai.Source time functions of the1999,Jiji(Chi-chi)earthquake from GDSNlong pe-riod waveform data using aftershocks as empirical Green’s function[J].Acta Seismologica Sinica,2002,24(2):113-125.(in Chinese)
7 李延兴,黄?,胡新康,等.板内块体的刚性弹塑性运动模型与中国大陆主要块体的应变状态[J].地震学报.2001,23(6):565~572.
7 Li Yanxing,Huang Cheng,Hu Xinkang,et al.The rigid and elastic-plastic model of the blocks in intro-plate and strain status of principal blocks in the continent of China[J].Acta Seismologica Sinica,2001,23(6):565-572.(in Chinese)
8 李延兴,胡新康,李智,等.台海地区的地壳运动与变形[J].地震学报,2002,24(5):487~495.
8 Li Yanxing,Hu Xinkang,Li Zhi,et al.Crustal movement and deformation in Taiwan and its coastal area[J].Acta Seismologica Sinica,2002,24(5):487-495.(in Chi-nese)
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