【摘要】 利用2001年昆仑山口西MS8.1地震现场观测所提供的地表破裂同震位移数据,使用简单滑移弱化破裂模型,估算了发震主断层上的破裂传播速度.该模型中考虑了断层破裂时动摩擦过程中应力上调和下调机制对地震波辐射能量分配的影响.对比Bouchon和Vallée有关昆仑山口西地震主断层破裂传播速度超过剪切波速度,甚至达到P波速度的结果,采用动摩擦应力下调时的滑移弱化模型(分数应力降模型),结果表明,伴随较高的地震波辐射效率,主断层的平均破裂传播速度等于或小于瑞利波速度,这与许力生和陈运泰的体波反演结果,以及陈学忠震源应力场估算的结果是一致的.最后,联系到由地表破裂现象所反映出的断层力学特征,如与视应力相关的分数应力降(动摩擦应力下调),基于滑移弱化模型,讨论了可能的震源破裂机制.更多还原

【Abstract】 With the co-seismic surface rupture slip displacements provided by the field observation for the 2001 MS8.1 Western Kunlun Mountain Pass earthquake, this paper estimate the rupture speed on the main faulting segment with a long straight fault trace on the surface based on the simple slip-weakening rupture model, in which the frictional overshoot or undershoot are involved in the consideration of energy partition during the earthquake faulting. In contrast to the study of Bouchon and Vallee in which the rupture propagation along the main fault could exceed the local shear-wave speed, perhaps reach the P-wave speed on a certain section of the fault, our results show that, under the slip-weakening assumption combined with a frictional undershoot (partial stress drop model), the average rupture speed should be equal to or less than the Rayleigh wave speed with a high seismic radiation efficiency, which is consistent with the result derived by waveform inversion and the result estimated from source stress field. In consideration of the surface rupture behavior, such as partial stress drop (frictional undershoot) associated with the apparent stress, an alternative rupture mechanism based on the slip-weakening model has also been discussed in this paper.更多还原