摘要
考虑地震是由于震源材料软化导致的一种基本机制,假设区域构造应力场在地震孕育过程中基本不变,震源区震前存在着热异常.我们根据热弹塑性增量理论,提出了两种材料模型,用弹塑性有限单元法模拟热状态对地震发生的影响. 模型1用来模拟断层外部区域的物质,其强度只和塑性变形有关而与热状态无关;模型2用来模拟断层物质,其强度只同热状态有关而与塑性变形无关.断层外部地震的发生被认为是岩石应变软化的结果;而断层内部地震的发生被认为是断层热软化的结果. 本文用上述模型分析了只有单一断层的热软化情况,并且得到了相应的断层错距、应力降和地震距.
Considering the basic earthquake mechanism to be due to the material softening at the focal region, we propose two models in the finite element scheme to simulate the effects of thermal state on earthquake occurrence. The tectonic stress field is assumed to remain constant during such a process, but a change of temperature at the focal region will cause a thermal stress field locally to be superposed on the tectonic stress field. The faulting plane is simulated by a joint element which under the influence of the stress field will deform elastically at first, then plastically and finally into the softening stage. Two material models are hereby proposed for the focal region. In model 1, the material strength parameters are independent of the temperature change but the material softening is related to the plastic volumetric strain resulting from the displacement field, the model is used outside the fault zone. In model 2, the material parameters are independent of the plastic volumetric strain but is related to the temperature change that causes thermal softening, the model is used inside the fault zone. The nonlinear models are employed to analyse the displacement and stress field due to the dislocation movement of the faulting plane. An incremental thermo-elasto-plasticity theory is used. The results of the simulations are compared and discussed.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
1992年第2期204-213,共10页
Chinese Journal of Geophysics
关键词
震源
热软化
地震
有限元法
Focal region, Thermal solftening, Earthquake, Finite element method.
