地震活动频次场研究

对7次7级地震和不同地区的8次6级地震研究频次场的自然正交函数展开问题。结果表明, 频次场时间因子异常具有多分量显示的特点, 大地震前频次场的前4个典型场中有3～4个典型场的时间因子发生异常变化, 特别是第一和第二个两个贡献率最大的典型场时间因子必定显示出异常变化, 异常典型场占总场的比例一般在80%以上。频次场时间因子变化比较敏感, 曲线起伏较大, 异常变化形态复杂多样。频次场时间因子异常表现出中期、 短期和短临性质的异常变化。采用较大起始震级进行频次场分析能使异常的特征更清晰、 更突出。分析地震频次场时的网格划分往往大于分析地震能量场的网格划分。

Study on Frequency Field of Seismic Activity

Study on the problem in natural orthogonal function expansion about frequency field of 7 earthquakes with magnitude of 7 and 8 earthquakes with magnitude of 6 in different regions has been done. The results show that the frequency field time factor anomalies have characteristics of multi-component display. 3~4 of the first 4 typical frequency fields have showed abnormal changes before large earthquakes. In particular, the first and second typical field time factors with the largest contribution rate must show abnormal changes. The proportion of abnormal typical field to total field is generally over 80%. The frequency field time factor is sensitive and its curves fluctuate greatly, with complex and diverse abnormal change patterns. The frequency field time factor could show abnormal changes in the mid-term, short-term and short-impending properties. If the frequency field analysis is done with larger initial magnitude, the abnormal features can be clearer and more prominent. The grid division when analyzing seismic frequency field is often larger than that in seismic energy field.