类乌齐-玉树-玛多剖面重力异常研究
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摘要
青海玉树Ms7.1地震发生在巴彦喀拉块体的甘孜-玉树断裂带上。对跨断裂带的重力剖面测线进行了相对重力联测,对观测结果作了大气改正、极移改正、漂移改正,经平差计算后,获取了该剖面的自由空气异常;结合该区1″×1″的ASTER GDEM(2009)地形数字模型,对自由空气异常作了曲率改正、平板改正及高精度的地形改正,得到该探测剖面的完全布格重力异常。分析结果表明:从布格异常的陡变区可初步推断出与地质研究结果一致的断裂构造的位置;在玉树附近沿剖面往东北向出现地壳基底抬升现象,并在清水河附近幅度达到最大,初步推断为印度地壳的俯冲下插对青藏高原东缘的抬升作用的结果。
Yushu Ms7.1 earthquake occurred in the Bayan Har block,exactly the Ganzi-Yushu fault zone.We set up a relative gravity survey lines cross the fault zone and conducted the gravity survey.We processed the raw data,such as atmospheric correction,polar motion correction,drift correction,adjustment calculation,and then obtained the free air anomaly of the profile.After the curvature correction,flat-panel and high-precision terrain correction by using the ASTER GDEM(2009) Digital terrain model(1 ″× 1″),we obtained a complete profile of the probe Bouguer gravity anomaly.The results show that the location of faults which consistents with the geological results as their is a sudden change zone in the Bouguer anomaly curve;the basement begins to uplift from the place near Yushu to its northeast along the profile,and the maximum rate is at Qingshuihe town.We have concluded that it is resulted from the Indian crust subducting and inserting,making the eastern edge of Qinghai-Tibet Plateau uplifting.
Yushu Ms7.1 earthquake occurred in the Bayan Har block,exactly the Ganzi-Yushu fault zone.We set up a relative gravity survey lines cross the fault zone and conducted the gravity survey.We processed the raw data,such as atmospheric correction,polar motion correction,drift correction,adjustment calculation,and then obtained the free air anomaly of the profile.After the curvature correction,flat-panel and high-precision terrain correction by using the ASTER GDEM(2009) Digital terrain model(1 ″× 1″),we obtained a complete profile of the probe Bouguer gravity anomaly.The results show that the location of faults which consistents with the geological results as their is a sudden change zone in the Bouguer anomaly curve;the basement begins to uplift from the place near Yushu to its northeast along the profile,and the maximum rate is at Qingshuihe town.We have concluded that it is resulted from the Indian crust subducting and inserting,making the eastern edge of Qinghai-Tibet Plateau uplifting.
引文
1陈立春,等.玉树Ms7.1级地震地表破裂与历史大地震[J].科学通报,2010,55(13):1 200-1 205.(Chen Li-chun,et al.The Ms7.1 Yushu earthquake surface ruptureand large historical earthquakes on the Garze-Yushu fault[J].Chinese Science Bulletin,2010,55(13):1 200-1 205)
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4彭华等.甘孜-玉树断裂带第四纪活动特征[J].地质力学学报,2006,12(3):295-304.(Peng hua,et al.Character-istics of quaternary activities of the Ganze-Yushu fault zone[J].Journal of Geomechanics,2006,12(3):295-304)
5冉洪流,何宏林.鲜水河断裂带北西段不同破裂源强震震级(M≥6.7)及复发间隔研究[J].地球物理学报,2006,49(1):153-161.(Ran Hongliu and He Honglin.Re-search on the magnitude and recurrence interval of character-ized earthquakes with M≥6.7 along the north western por-tion of the Xianshuihe fault zone in western Sichuan,China[J].Chinese Journal of Geophysics,2006,49(1):153-161)
6 Kane M F.A comprehensive system of terrain corrections u-sing a digital computer[J].Geophysics,1962,27:455-462.
7 Nagy D.The gravitational attraction of a right rectangularprism[J].Geophysics,1966,31:362-371.
8李闽峰,等.玉树断裂活动性研究[J].地震地质,1995,17(3):218-224.(Li Minfeng,et al.Research on activity ofyushu fault[J].Seismology and Geology,1995,17(3):218-224)
9王有学,等.青海东部地壳速度结构特征研究[J].地学前缘,2000,7(4):568-579.(Wang Youxue,et al Study ofcrustal velocity structure in east Qinghai[J].Earth ScienceFrontiers,2000,7(4):568-579)
10王阎昭,等.基于GPS资料约束反演川滇地区主要断裂现今活动速率[J].中国科学D辑:地球科学,2008,38(5):582-597.(Wang Yanzhao,et al.Inversion of pres-ent-day rates of major faults of the region in Sichuan-Yun-nan province constrained by GPS[J].Science in China,2008,38(5):582-597)
11王刚,等.青藏高原腹地中新世从造山阶段向造高原阶段的转变及动力学机制[J].地球物理学报,2010,53(6):1384-1398.(Wang Gang,et al.The deformationtransfer from orogen stage to plateau stage in the centralpart of Tibetan Plateau during Miocene time and it’s tec-tonic mechanism[J].Chinese Journal of Geophysics,2010,53(6):1 384-1 398)
2闻学泽.甘孜-玉树断裂带的新构造特征与地震危险估计[J].地震地质,1985,7(3):23-32.(Wen xueze,et al.Neotectonic features of the Ganzi-Yushu fault zone and as-sessment of its earthquake risk[J].Seismology and Geolo-gy,1985,7(3):23-32)
3周荣军,等.甘孜-玉树断裂带的近代地震与未来地震趋势估计[J].地震地质,1997,19(2):l15-124.(ZhouRongjun,et al.Recent earthquakes and assessment of seis-mic tendency on the Ganzi-Yushu fault zone[J].Seismologyand Geology,1997,19(2):l15-124)
4彭华等.甘孜-玉树断裂带第四纪活动特征[J].地质力学学报,2006,12(3):295-304.(Peng hua,et al.Character-istics of quaternary activities of the Ganze-Yushu fault zone[J].Journal of Geomechanics,2006,12(3):295-304)
5冉洪流,何宏林.鲜水河断裂带北西段不同破裂源强震震级(M≥6.7)及复发间隔研究[J].地球物理学报,2006,49(1):153-161.(Ran Hongliu and He Honglin.Re-search on the magnitude and recurrence interval of character-ized earthquakes with M≥6.7 along the north western por-tion of the Xianshuihe fault zone in western Sichuan,China[J].Chinese Journal of Geophysics,2006,49(1):153-161)
6 Kane M F.A comprehensive system of terrain corrections u-sing a digital computer[J].Geophysics,1962,27:455-462.
7 Nagy D.The gravitational attraction of a right rectangularprism[J].Geophysics,1966,31:362-371.
8李闽峰,等.玉树断裂活动性研究[J].地震地质,1995,17(3):218-224.(Li Minfeng,et al.Research on activity ofyushu fault[J].Seismology and Geology,1995,17(3):218-224)
9王有学,等.青海东部地壳速度结构特征研究[J].地学前缘,2000,7(4):568-579.(Wang Youxue,et al Study ofcrustal velocity structure in east Qinghai[J].Earth ScienceFrontiers,2000,7(4):568-579)
10王阎昭,等.基于GPS资料约束反演川滇地区主要断裂现今活动速率[J].中国科学D辑:地球科学,2008,38(5):582-597.(Wang Yanzhao,et al.Inversion of pres-ent-day rates of major faults of the region in Sichuan-Yun-nan province constrained by GPS[J].Science in China,2008,38(5):582-597)
11王刚,等.青藏高原腹地中新世从造山阶段向造高原阶段的转变及动力学机制[J].地球物理学报,2010,53(6):1384-1398.(Wang Gang,et al.The deformationtransfer from orogen stage to plateau stage in the centralpart of Tibetan Plateau during Miocene time and it’s tec-tonic mechanism[J].Chinese Journal of Geophysics,2010,53(6):1 384-1 398)
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