基于同震GPS数据的汶川大震同震应变特征研究

Research on the Coseismic Characteristics of Strain of the Wenchuan Earthquake Based on GPS Data

利用同震GPS观测数据,采用多面函数法,以数据分片拟合方式对2008年5月12日汶川MS8.0大震同震面应变进行计算,评定了计算结果的精度,并分析与强震有关的面应变变化特征。结果表明:在计算同震应变变化时,分片拟合较整体拟合得到的应变结果精度更高;同震应变结果对龙门山断裂能量释放特征及地表破坏分布有一定的反映。

In this paper, coseismic GPS data and the multisurface function are first used to calcu- late the coseismic surface strain caused by the Ms8.0 Wenchuan earthquake that occurred on May 12, 2008 based on a piecewise data fitting method. The accuracy of the calculations is assessed, and the variation characteristics of surface strain related to the earthquake are analyzed. Calcula- tion of coseismic strain changes revealed that the strain results obtained by piecewise fitting way are more precise than those determined by overall fitting. The calculation results of the two fit- ting methods feature the same order of magnitude, and the spatial distributions of the two images show some similarity. Compared with the results of the overall fitting method of multidimension- al functions, the coseismic surface strain expansion and compression zones determined by the piecewise fitting method are more concentrated in the spatial distribution image. The results of this paper were compared with those of numerical simulation, and findings indicated that the cal- culation results of piecewise fitting are reliable. Coseismic strain appears to reflect the energy release characteristics and ground destruction distributionof the Longmenshan fault. The Wen chuan earthquake caused intense crustal shortening in the northern region of the Longmenshan fault zone. After the earthquake, the I.ongmenshan sub block and the Sichuan basin sub-block moved in opposite directions with high speed over a short period of time. In the near field region, several major aftershocks occurred in some areas where the coseismic horizontal displacement is amplitude. The coseismic surface strain highlights the right lateral slip characteristic of Wenchuan earthquake and the characteristics of uneven compression at the northwestern side of the I.ong menshan fauh zone are demonstrated. The results show different strain attenuation characteristics at both sides of the I.ongmenshan fault. Taken together, findings in this study may be used to de termine the characteristics of horizontal crustal movement caused by the Ms8.0 Wenchuan earth- quake in a more intuitive manner.