用数字地震资料研究永胜地震余震序列的应力场

Study on Stress Field of Aftershock Sequence of the Yongsheng Earthquake through Digital-Recorded Data

以Brune中小地震圆盘形破裂位错模式为基础 ,用地面运动峰值参数 (r v)直接求出震源处应力降Δσ和环境应力τ0 值的新方法 ,并利用永胜MS6 0级地震序列的数字化资料 ,给出了该次序列的Δσ多数在0 0 5～ 0 5MPa之间 ,平均值为 0 2 4MPa;τ0 值多数在 0 5～ 2 0τ0 MPa之间 ,平均值为 1 0 7MPa。通过对该区Δσ和τ0 值的时空分析 ,认为永胜地震余震序列是一次比较典型的低应力、低强度序列 ,主震后应力释放很快 ,较为彻底。

Based on Burne's mode of disk-shaped dislocation for moderate and small earthquakes, the environment stress values (τ 0) and stress drops (Δσ) at source area are calculated directly through using the peak para meters of ground motion. Using recorded digital data for the aftershock sequence of M S 6 0 Yongsheng Earthquake, the Δσ values for this seq uence have been calculated and they are in the range from 0 05MPa to 0 50MPa. The average Δσ is 0 24MPa. In the mean time, τ 0 values also have been calculated with same method and they are in the range from 0 5M pa to 2 0MPa.The average τ 0 is 1 07MPa. The analysis o f spatial and temporal features of Δσ values and τ 0 value s suggests that the sequence of Yongsheng Earthquake belongs to the typical low- stress and low-strength sequence. The stress releases rapidly after the main ear thquake's occurrence.