摘要:
从应力降的静态理论,讨论了地震应力降的精度,并利用野外观测的最大位移和由地震波得到的地震矩,分别计算了十个研究较充分的地震应力降.对不同作者的结果作了比较,可以看出,应力降有因子为2的变化范围.但从统计观点看,地震应力降是分布在几巴到几百巴的数量级,大多数位于20-60巴;总结了地壳中代表性岩石在地壳温度、压力条件下,粘滑及脆性剪切破裂时的应力降,它们与温度、压力、岩性、含水矿物的存在有关.取值范围是从零到几千巴数量级;讨论了地震断层的物理状态,指出地震应力降是一种平均结果,并由于静态理论忽略了断层面破裂所消耗的能量,所以地震应力降比实际的应力降要低.
Abstract:
The uncertainties of earthquake stress drop based on static dislocation theory were discussed. The stress drops of ten earthquakes having surface breakage were studied in detail and calculated using the fault parameters obtained from field observations and the earthquake moment obtained from seismic waves. Comparison of the stress drops obtained by diferent authors was made. It is clear that the value of a stress drop may vary by factor of two. But from the statistical point of view, the stress drops were distributed in a range from a few bars to a few hundred bars and most of them lie within the range of 20-60 bars. The stress drops for stick-slip and brittle shear fracture in rock experiments carried out under conditions similar to the crust for typical rocks in the crust were reviewed. It shows that the stress drops are dependent on the pressure, temperature, type of rocks, pore pressure, and the existence of the hydrous minerals etc., their values lie in the range from zero to a few thousand bars. The physical state of the earthquake faults have been discussed, the earthquake stress drop is an average value of the various stress drop's values on the fault plane. It was also pointed out that the earthquake stress drop obtained from static theory is lower than the actual value because the static theory did not take account of the energy dissipated in the fracture of fault plane.
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