| 其他摘要 | As we enter the 21st century, when the Earth's ?nite resources will be further strained by the explosive population growth, earth scientists are undertaking more and more responsibilities for striving to better understand our dynamic planet. Given that most earthquakes and volcanic eruptions do not strike randomly but occur in speci?c areas, such as along plate boundaries, it is necessary to develop a theory that might be able to explain how our earth works. Over the past ?fty years, a quite few of theories about tectonic plate have been formulated as two distinct types of plate kinematic models, which are based on geological measurements and observations from space geodetic surveying respectively. In order to demonstrate the current motion of these tectonic plates on the surface of our planet, a mass of available GPS observational data have been applied to the calculation of kinematic parameters in this paper. The kinematical parameters for 13 major global plates including Amurian, Antarctic, Arabia, Australia, Eurasia, India, N.America, Nazca, Nubia, Paci?c, S.America, Somalia and Sundaland within NNR-MORVEL56 plate motion model have been estimated in this paper, using the velocities from 225 GPS stations with respect to ITRF2008. Here a di?erent method for determining whether stations are located in a rigid plate has been used, which avoids the di?culties caused by the traditional site selection criteria concerning that how far stations should be away from the plate boundaries. It is of great signi?cance to initiate a new criteria that stations with second invariant strain rate(SISR) greater than 10^?14/yr is supposed to be eliminated, according to the GSRMv1.2(Global Strain Rate Model) delineating the strain rate over the globe. Another improvement in this paper is the application of the ICE3G-VM2 model containing ice model and earth model, where stations with additional horizontal velocity greater than 0.5mm/yr have been ignored instead of modifying a station’s velocity owing to the e?ect of the GIA(Glacial Isostatic Adjustment). Last but not the least,compared with the relatively old-fashioned plate motion model, NNR-NUVEL1A published in the year of 1994, NNR-MORVEL56 that was released in the year of 2010 has been regarded as the primary referenced model in this paper. To derive a absolute plate motion model in a NNR(No-Net-Rotation) reference frame, however, the inertia tensors are always considered as indispensable attribute of all these plates. In this paper, evaluation for the Euler vectors of 13 plates was followed by the computation of the geometric parameters of each plate within NNR-MORVEL56, including the area and 6 components of the inertia tensor. The computational approaches are mainly built on a triangulation algorithm and the adaptive Simpson’s double integral method for spherical polygons, which produces highly reliable results for all 56 modern plates. In addition, the Euler vectors and their uncertainty for the 6 active block regions, including Himalayan-Tibet, Yunnan-Sichuan, Qilian-Altyn, Tianshan-Tarim, North China, and South China were also calculated, using 329 GPS horizontal velocities relative to the background of Eurasia plate, together with the intraplate deformation parameters, containing the second invariant strain rate,rotation rate, delatation rate, the maximum shear strain rate, the principal extensional strain rate(PESR), the principal compressional strain rate, and the principal direction for the PESR, given the 341 GPS horizontal velocities available in the Chinese mainland. When estimating strain rates of stations or grid nodes in a speci?ed plate, a somewhat di?erent method based on the velocity gradient tensor ?eld has been used in this paper, rather than on the calculation for the average strain parameters throughout the whole plate, which used to be based on even strain model and the second order strain model. All of the results and conclusions in this paper may be able to |
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