An Overview of the Study on Stress Magnitude

Crustal stress field holds an important position in geodynamics research, such as in plate motion simulations, uplift of the Qinghai-Xizang (Tibet) Plateau and earthquake preparation and occurrence. However, most of the crustal stress studies emphasize particularly on the determination of stress direction, with little study being done on stress magnitude at present. After reviewing ideas on a stress magnitude study from geological, geophysical and various other aspects, a method to estimate the stress magnitude in the source region according to the deflection of stress direction before and after large earthquakes and the stress drop tensor of earthquake rupture has been developed. The proposed method can also be supplemented by the average apparent stress before and after large earthquakes. The stress direction deflection before and after large earthquakes can be inverted by massive focal mechanisms of foreshocks and aftershocks and the stress drop field generated by the seismic source can be calculated by the detailed distribution of the earthquake's rupture. The mathematical relationship can then be constructed between the stress drop field, where its magnitude and direction are known and the stress tensor before and after large earthquakes, where its direction is known but magnitude is unknown, thereby obtaining the stress magnitude. The average apparent stress before and after large earthquakes can be obtained by using the catalog of broadband radiated energy and seismic moment tensor of foreshocks and aftershocks and the different responses to stress drops. This relationship leads to another estimation of stress magnitude before a large earthquake. The stress magnitude and its error are constrained by combining the two methods, which provide new constraints for the geodyuamics study.

作 者： Sheng Shuzhong Wan Yongge   作者单位： Sheng Shuzhong(Institute of Disaster Prevention Science and Technology, Yanjiao 065201, Hebei, China)

Wan Yongge(Institute of Geophysics, China Earthquake Administration, Beijing 100081, China) 

刊 名： 中国地震研究（英文版）  英文刊名： EARTHQUAKE RESEARCH IN CHINA  年，卷(期)： 2009 23(2)  分类号： P3  关键词： Deflection of stress direction   Average apparent stress   Stress magnitude  

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