In this paper, the approaches adopted for the extraction of earthquake-induced features from ionospheric irregularities like spread F and sporadic E are discussed. For this purpose, a few Japan earthquakes (EQ) with magnitude M > 7 are selected. The selection procedures for identifying earthquake-induced effects in these irregularity parameters are discussed, and the EQ time signature in these irregularities is then defined as enhancement in fxI and foEs prior to an earthquake. The analysis output shows that the critical frequency of spread F index increases by 16–83%, 3–5 days prior to the earthquakes and the critical frequency of sporadic E increases by 50–110%, 2–4 days prior to the EQ. In case of May 30, 2015, Japan EQ with M = 7.8, the critical frequency of sporadic E increased up to 18 MHz prior to an EQ.

本文讨论了从电离层不规则像散布F和零星E中提取地震诱发特征的方法。为此，选择了几级M> 7的日本地震（EQ）。讨论了识别这些不规则性参数中地震引起的影响的选择程序，然后将这些不规则性中的EQ时标定义为地震前fxI和foE的增强。分析结果表明，在地震发生前3-5天，扩展F指数的临界频率增加了16–83％，而在EQ发生前2-4天，零星E的临界频率增加了50–110％。在2015年5月30日的日本EQ中，M = 7.8，零星E的临界频率在EQ之前增加到18 MHz。