【摘要】 地壳应力场在板块运动模拟、青藏高原隆升、地震孕育和发生等地球动力学研究中具有重要地位。而目前大多数地壳应力方面的研究侧重于方向的确定,对应力量值研究甚少。我们总结了地质、地球物理等方法确定应力量值的思路,在此基础上提出了根据大地震前后应力方向变化和地震破裂应力降张量估计地震震源附近应力量值,并辅以地震前后平均视应力方法等其他方法共同对应力量值进行进一步约束的思路。大地震前后的应力方向变化根据大量前震和余震的震源机制给出,地震破裂造成的应力降场可根据地震破裂详细分布计算,则已知大小和方向的地震应力降场与方向已知、大小未知的地震前后应力张量之间可以构建数学关系,从而得到应力量值。根据地震前震和余震的宽频带辐射能量和地震矩张量目录得到大地震前后的平均视应力,两者之差对应于地震应力降,根据这种关系得到震前应力量值的另一个估计。两种方法相结合,给出应力量值及误差估计,为地球动力学研究提供新的约束。更多还原

【Abstract】 Crustal stress field has an important position in geodynamics research, such as plate motion simulation, uplift of the Tibet Plateau and earthquake preparation and occurrence, etc. However, most of the crustal stress studies emphasize particularly on the determination of stress direction, little study on stress magnitude has been done at present. We summed up the ideas on stress magnitude study on geological, geophysical and other method, and propose a method to estimate the stress magnitude in source region according to the deflection of stress direction before and after large earthquakes and the stress drop tensor of earthquake rupture. The proposed method can also be supplemented by the average apparent stress before and after large earthquakes, and other methods. The stress direction deflection before and after large earthquakes can be inverted by massive focal mechanisms of foreshocks and aftershocks, the stress drop field generated by seismic source can be calculated by the detailed distribution of earthquake rupture, then the mathematical relationship can be constructed between the stress drop field, whose magnitude and direction are known, and the stress tensor before and after large earthquakes, whose direction is known but magnitude is unknown, thereby the stress magnitude is obtained. The average apparent stress before and after the large earthquake can be obtained by using the catalog of broadband radiated energy and seismic moment tensor of foreshocks and aftershocks, and their difference correspond to stress drop. This relationship leads to another estimation of stress magnitude before the large earthquake. The stress magnitude and its error are constrained by combination the two methods, which provide new constraints for the geodynamics study.更多还原