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本文讨论了利用破裂力学理论说明地震破裂的过程,认为地震本质上是岩石在应力作用下的低应力破裂现象.它是岩石中的裂纹不断稳态扩展、最后进入失稳扩展的结果.分析了在扩展过程中应力和位移的变化,发现任何将要破裂的那一点的应力都要由初始应力τ_(?)升高到屈服应力τ_y 以后才破裂,破裂后裂纹面上的点的应力降到0.在破裂前和破裂后的位移,都可由弹性力学方程给出.在破裂的一瞬间破裂的端点产生的非弹性位移,则不能由弹性力学方程给出.它可以由断裂力学中的裂纹滑开位移公式近似给出.根据位错模式由于计算弹性波辐射场的位错量 D(ξ,t),正是破裂瞬间产生的非弹性位移,所以用弹性位移公式来计算地震位错量是错误的.我们采用了裂纹滑开位移公式来计算地震位错量,从而导出了较合理的计算地震释放总能量的公式 E_T=τ_y(?)S(τ_y 为屈服强度;(?)为平均位错;S 为断层面积)以及估算初始应力值τ_0的公式:τ_0 =[D_(max)/L·4μτ_y/(1-ν)π ]~(1/2)(L 为断层长度).用它们计算了一些地震的 E_r 和τ_0,分别列于表1和表2.这些结果比以往的结果要更合理一些。 结果表明:(1)地震多数是在低应力作用下(即低初始应力)发生的(约100—200巴);(2)地震释放的总能量约比地震波能量大一个数量级.
This paper discusses the use of fracture mechanics theory to explain the process of earthquake rupture, that the earthquake is essentially the rock under the stress of low stress rupture phenomenon, which is the steady crack growth in the rock, and finally into the unstable expansion of the results analyzed In the process of expansion, the stress and displacement change, it is found that the stress at any crack point should be ruptured from the initial stress τ_ (?) Up to the yield stress τ_y. The stress at the crack surface after fracture is reduced to 0 The displacements before and after rupture can be given by the elastic mechanics equations.The inelastic displacements at the end of rupture at the moment of rupture can not be given by the elastic mechanics equations which can be derived from the crack propagation in fracture mechanics Displacement formula is approximately given.According to the dislocation model due to the calculation of elastic wave radiation field dislocation D (ξ, t), it is the moment of rupture generated inelastic displacement, so the elastic displacement formula to calculate the amount of seismic dislocation is We use the crack slip displacement formula to calculate the amount of seismic dislocation, which leads to a more reasonable formula to calculate the total energy of seismic release E_T = τ_y (?) S (τ_y is the yield strength; (?) Is the average dislocation; S is the fault area), and the formula for estimating the initial stress value τ_0: τ_0 = [D max / L 4μτ_y / (1 -ν) π] Fault length). Using them, E_r and τ_0 for some earthquakes are calculated, as shown in Table 1 and Table 2. These results are more reasonable than previous results. The results show that: (1) most of the earthquakes occur under low stress (ie low initial stress) (about 100-200 bar); (2) the total energy released by earthquakes is about one order of magnitude larger than the seismic energy.