山西地区视应力时空变化特征分析

Space-time characteristics analysis of the apparent stress in Shanxi

摘要:

利用2001 ～ 2011 年ML≥2. 0 地震波形资料计算得到山西地区的视应力，结合山西地区2001 年以来5 次M4. 5 以上地震探讨地震前后视应力时空变化特征后发现，在5 次4. 5 级以上地震前1 年均出现过视应力高值，地震发生在高值异常下降的过程中，且这5 次中等地震发生在视应力高值异常区域内或附近。结果表明视应力高值异常区对中强震的震中预测具有一定的指示作用，可以作为地震危险性判定的参考依据。

Abstract:

According to the Brune model，we calculated the near source apparent stress of earthquakes with ML≥2. 0 which occurred during 2001 ～ 2011 and analyzed the temporal and spatial variations of apparent stress in Shanxi Province． The waveform data are gotten from the Digital Seismic Network of Earthquake Administration of Shanxi Province． We discussed the difference of apparent stress values before and after M≥4. 5 earthquakes since 2001． The timedependent apparent stress curves show that high apparent stress value occurred one year before five earthquakes with magnitude larger than M4. 5． The apparent stress values at the source areas follow a pattern which increases first and then decreases; the spatial change of apparent stress shows that highly centralized large apparent stress values and large apparent stress gradients are found at near source area before five M≥4. 5 earthquakes，and the earthquakes occurred at the area which has large apparent stress gradients，which implies high energy accumulation and apparent tectonic stress increasing in the source area． The change of apparent stress values illustrate the stress evolution progress in the source area，which can be used in seismic risk analysis．