应力调制与预报研究

在地球动力作用和地壳运动的过程中构造块体呈现出整体运动的特征,表现在大陆地震的动力学特征具有明显的分区性。因而,大陆每个块体的应力场特征方向与强地震发生的主要构造力方向一致性较好。在它的作用下,块体边界或某些部位出现应力不均匀并有应变能的积累。孕震区应变能由线性积累向临界的非线性转化迹象会表现在弱震活动与主构造方向上固体潮交变应力场的呼应上。 交变应力场可加强孕震区应力集中部位的介质疲劳强度,从而在这些部位触发一些弱震,而且在附加应力场分别为正、负构造应力场方向时发生的弱震频次比例失调,这一过程与构造应力场的呼应显示了强震前弱震震源机制一致性较好的前兆特征,这种情形下的地震活动反映了一种应力调制作用,分析了1970年来的华北资料和1980年来的云南省资料,用直接图像分布、数值和等值线等3种方式讨论,表明它对强震有1~3年的中长期预报意义,R值评估均大于0.5。

Stress modulation and prediction research

The tectonic blocks show the characteristics of integral movement during the crustal movement and under dynamic process of the Earth.It shows that the dynamic characteristic direction is distributed with regionalizaion. Thus, the stress field characteristic direction of each block is similar with the main structure force direction where strong earthquakes happen.The stress non-uniformity and accumulation of energy on the boundary or in certain parts of some blocks appear.The sign when the lineal accumulation transforms to the non-lineal critical situation comports at this echo that the weak seismic activity associated with the solid tide alternating stress field along the main tectonic direction.The medium fatigue strength increases in an alternating stress field, and then some weak events are triggered.So the seismic frequency proportion is maladjusted when the appendant stress field direction is positive or negative main tectonic direction;this also indicates the coherence of most foreshock mechanism.Using this idea of stress modulating action the data of North China region and Yunnan province are analyzed by three ways.The result indicates that it is significant for long-and medium-term prediction.The R-value is bigger than 0.5.