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青藏高原下地壳黏滞系数究竟是多少,已成为深入定量研究中的突出问题,它的数值量级将极大地影响定量模拟的结果.为了获得青藏高原下地壳的黏滞系数,从3条途径对该参数进行了计算:一是基于对青藏高原深部温度状态改进了的估计,用流变定律和GPS求得的应变速率对高原北部下地壳黏滞系数重新进行了估算,获得的昆仑山地区中地壳等效黏滞系数为1020~1022Pa·s量级,下地壳等效黏滞系数在1019~1021Pa·s之间.二是用3种流变模型对2001年昆仑山MS8.1级地震震后跨断层GPS站点记录到的震后变形进行了模拟,得到的下地壳黏滞系数为1017Pa·s量级.三是用黏弹性模型对炉霍地震后的跨断层形变曲线进行了拟合,得到的下地壳黏滞系数为1019Pa·s量级.前人研究等效黏滞系数时忽视了等效黏滞系数与应变速率存在的非线性关系,本研究结果协调地解释了实验室实验、大地震后较短时期的变形和大地震后较长时间变形下,其等效黏滞系数存在差异的问题.
In the Qinghai-Tibet Plateau, whether the viscosity coefficient of the lower crust is large or not has become a prominent problem in in-depth quantitative research, and its numerical magnitude will greatly affect the quantitative simulation results.In order to obtain the viscous coefficient of the lower crust in the Qinghai-Tibet Plateau, The parameters are calculated. First, based on the improved estimation of the deep temperature in the Qinghai-Tibet Plateau, the viscosity of the lower crust in the northern plateau has been re-estimated by the rheological law and GPS strain rate. The obtained Kunlun Mountains The equivalent viscosity coefficient of the middle crust is in the order of 1020 ~ 1022Pa · s, and the equivalent viscosity coefficient of the lower crust is in the range of 1019 ~ 1021Pa · s. Second, three kinds of rheological models are used to simulate the Kunlun MS8.1 earthquake After the earthquake, the post-earthquake deformation recorded by the cross-fault GPS site was simulated and the lower crustal viscosity coefficient was found to be on the order of 1017 Pa · s. Thirdly, the viscoelastic model was used to fit the cross-section deformation curve after the Luhuo earthquake , The obtained lower crust has a viscosity coefficient of the order of 1019 Pa · s.While the previous study of the equivalent viscosity coefficient ignores the non-linear relationship between the equivalent viscosity coefficient and the strain rate, the results of this study coordinately explain the laboratory experiments After the earthquake Modification time is long and a short period after deformation earthquake, equivalent viscosity coefficient for discrepancies.