全球空间测地站矢量场对板块运动的描述及地幔的经、纬向流

从 2 0 0 1年IERS公布的ITRF参考框架系下的 4 32个空间测地站中以面积平均随机选用了111个站 ;这些点的站速度矢量图描述了北半球欧亚 (EA)、北美 (NA)和北太平洋 (NP)三大板块的运动态势 :以北大西洋洋脊为轴 ,欧亚板块向NE—E—SE运动 ;北美板块向NW—W—SW运动 ,呈绵羊角式张裂运动 ,两者在大西洋两侧的N向运动越过极区后 ,汇集指向阿留申 ;北太平洋板块以超过北美板块和欧亚板块 6倍左右的速度向NWW运动 ,与欧亚板块呈正面碰撞型关系 ,表现为大洋壳的深俯冲与大陆壳仰冲 ;北太平洋板块与北美板块以圣安德烈斯断层为界呈剪切拉张型关系。文中描述了南半球南美 (SA)、非洲 (AF)、阿拉伯 (AR)、印—澳 (IN—AU)和东南太平洋 (SP)的运动态势 :以东南太平洋洋脊为轴 ,其东侧的纳兹卡 (NZ)板块高速向东运动 ,而其前方的南美、非洲、阿拉伯和印—澳等板块则向NE—NNE运动 ,速度依次增高 ,可能与其间的大西洋洋脊、印度洋洋脊和红海裂谷张裂的正、反向叠加作用有关。西南太平洋与澳大利亚板块的东北缘和东缘均呈强碰撞强剪切型运动关系 ,而纳兹卡板块与北美板块呈追尾型运动关系。南极板块 (Ant)从环南极洋脊的东南太平洋段为起点向南运动 ,过南极后继续向北、向非洲、印度洋方向运动 ,并略显右旋。上述板?

THE PRESENT PLATE MOVEMENTS SHOWN BY GPS VECTOR FIELDS AND THE MODEL OF THE COMBINED LATITUDINAL AND LONGITUDINAL MANTLE FLOW

The horizontal velocities of 111 stations selected at random from 432 stations issued by IERS under the ITRF reference frame in 2001 are used to obtain the velocity field of the plate movement around the globe. The movements of Eurasian Plate(EA), North American(NA) and North Pacifica Plate(NP) in the north Hemisphere are shown by the velocity field, taking the Atlantic Ridge as axis, the EA moves northeastwards, eastwards and then southeastwards; the NA moves northwestwards, westwards and then southwestwards; so they show “sheep horn like” rifting movement between each other, the northward movements of the mantle shown by them across the North Pole to the Aleus Arc. The velocity of the NP moving to the NWW is about 6 times as much as those of the EA, NA etc; the collisional relationship between the NP and EA is shown by the deep subduction of the oceanic plate and thrusting of the continental plate; and the relationship between the NP and NA is the transtension shown by the movement of the San Andrews strike slip Fault which is the boundary between them. The plate movements of South American Plate (SA), African Plate (AF), Arabian Plate (AR), Indian—Australian Plate (IN—AU) and Southeast Pacific Plate (SP) in the south Hemisphere are also obtained: taking the southeast Pacific ridge as axis, the Nazcar Plate(NZ) to the east of the axis is moving by high speed to the east, however the SA, AF, AR and IN—AU to the east of the NZ are moving to the NE—NNE, their velocities become faster and faster eastwards; these phenomena may result from converging and opposite converging movements of the mantle imposed by the rifting of the Atlantic Ridge, Indian Ridge and Red Ocean Ridge among them. So strong collision and strike slip movements occur between the southwestern part of Pacific and the east and northeast edges of the AU; and the movements between the NZ and NA show the form of the “run and catch” type. The mantle under the Antarctica Plate (AP) is moving southwards from peri Antarctic Ridge in the southeastern Pacific Ocean, continuing moving to the north across the South Pole, then to Africa and the Indian Ocean, which also shows somewhat dextral rotation. The plate movements mentioned above also indicate the disharmony state of movements between the north and south hemispheres; there are 13 large en echelon active faults in this disharmony zone. Now, the latitudinal component of movement of the EA, NA and NP in the north hemisphere is more significant. However, except the SP, several large continental plates in the south hemisphere are moving to the northeast north northeast, namely the longitudinal component of movement is more important. And the Equator fault zone separates these two types of movements. Moreover, the mantle in the south and north hemispheres does not only flow along latitude and longitude separately; so the problems about the combined latitudinal and longitudinal mantle flow, the controls on the mantle flow and the four tectonic systems around the globe by the double asymmetry of the north/south hemispheres and the 0°/180°hemispheres need to be considered.