【摘要】 在前人关于于田地区地壳水平分层模型研究的基础上,结合于田台GPS连续观测资料粗略确定各层的粘滞系数。基于粘弹水平分层模型,分别计算了2008、2014年2次于田7.3级地震的粘弹同震库仑应力变化。基于粘弹库仑应力变化,采用"直接"余震频次的计算方法,得到了区域范围内与主震同震库仑应力变化直接相关的理论地震频次。提出了基于理论与实际地震频次对比以及理论与实际地震频次-距离衰减曲线拟合残差对比估计与主震同震库仑应力变化直接相关的后续最大地震震级的方法。不同方法的计算结果显示,与2008年于田7.3级地震同震库仑应力变化直接相关的最大后续地震震级为MS7.2~7.5,而2014年于田7.3级地震的最大后续震级估计为MS6.3。前者与2014年于田地震7.3的震级非常接近。由于震级相同、空间距离较近、时间间隔较短、区域外力作用相同、2次地震构造关联性较强且具有较明确的应力相互作用等,因而认为2008、2014年2次7.3级地震构成一对广义的双震型地震,这与该区域以往序列类型特点相吻合。对震级下限及G-R关系b值对结果的影响进行了初步讨论,结果显示,当粘弹同震库仑应力变化确定之后,震级下限对后续最大地震震级估计影响不大,但G-R关系b值对结果有较大影响。更多还原

【Abstract】 On the basis of previous studies on crustal horizontal layered model in the Yutian area,and together with continuous GPS observation of the Yutian seismic station,we roughly estimate viscosity coefficient of each layers. Based on the viscoelastic medium horizontal layered model,the viscoelasticity coseismic Coulomb stress changes of MS7. 3 earthquakes in 2008 and2014 in the Yutian area have been calculated separately. The frequency of "direct"aftershock has been calculated from the viscoelasticity coseismic Coulomb stress change,which directly related to the main shock Coulomb stress change in the study area. Further more,we propose a method to estimate the magnitude of the subsequent maximum earthquakes,by comparing the theoretic and actual earthquake frequency. The results show that the magnitude of the subsequent maximum earthquake caused by the coseismic Coulomb stress change of 2008 Yutian MS7. 3earthquake lies between MS7. 2 to MS7. 5,much more larger than that of actual earthquake with MS6. 3,but similar to the 2014 Yutian MS7. 3 earthquake. Since two Yutian MS7. 3 earthquakes have the same magnitude,closer spatial distance,shorter time interval,similar stress action and strong tectonic correlation,they can be seen as a generalized doublet events,consisting with the sequence type characteristics in this region. The effects of lower limit of magnitude and b-value of G-R relationship on the results have been discussed preliminary,and it shows that the lower limit of magnitude has little effect,but b-value has a greater influence on the results.更多还原