华北强震地形变及重力前兆特征与孕震机理

Precursory Characters and Earthquake Preparation Mechanism of Ground Deformation and Gravity Before Strong Earthquakes in North China

通过分析华北地区强震地形变及重力前兆特征，发现震前在较大范围内存在与构造密切相关的动力学过程；在震中区介质状态发生变化。在此基础上提出了改进的组合—硬化模式：调整单元的运动，牵动较大范围构造运动的加剧及断层两侧深层介质密度的变化；应力集中单元由于能量的不断积累，介质出现硬化过程。上述机理形成了前兆的各个阶段。

The precursory characters of ground deformation and gravity before strong earthquakes in North China have been analyzed.Dynamic process has close relations with tectonics that exists in large areas before strong earthquakes and the medium state variation exists in epicenter areas.On the basis of those mentioned above,an improved integration hardening model has been proposed.The movement of adjustment unit drags the boost of tectonic movement in large areas and the density changes of deep layer medium on both sides of the faults. Because of the continuous energy accumulation of stress concentration units,hardening process of medium emerges.The above mentioned mechanism forms the various steps of the precursor.