| 摘要: | 本論文將利用接受者操作特徵曲線(Receiver Operating Characteristic curve, ROC curve)統計研究台灣地區地震電離層前兆。中位數參考和z檢定將被用來偵測，台灣地區1994-1999年50筆規模M≥5.5地震期間的電離層F2層層峰電漿頻率和區域電離層GPS全電子含量(Total Electron Content)，以及1999-2014年129筆規模M≥5.5地震期間之全球電離層圖(Global Ionospheric Map, GIM)中TEC之電離層異常。首先，計算前1-15天移動中位數及其上下四分位間距，以建立參考並偵測增加異常(正異常)和減少異常(負異常)。藉由z檢定探討地震期間和整體觀測之異常發生，獲知負異常與正異常會分別顯著出現於地震前1-4天和23-28天。1994-1999年結果顯示F2層層峰電漿頻率負異常顯著出現於地震前1-3天之下午時段1200-2000 LT，而區域GPS TEC負異常則發生在地震前2-4天之下午時段1400-1600 LT。1999-2014結果則是GIM TEC負異常顯著出現在地震前1-3天下午時段1800-2200 LT。反觀正異常，其於1994-1999年F2層層峰電漿頻率會顯著出現於地震前15-17天之下午時段1300-1500 LT；1994-1999年區域GPS TEC，地震前24-28天，下午時段1200-1400 LT；1999-2014 GIM TEC，地震前23-28天，下午時段0900-1400 LT。進一步以地震前後7天、前後15天、前後30天等，建立參考，結果發現電離層正負異常之出現準30天周期特徵。ROC 曲線證實電離層異常前兆之出現正比於地震規模，顯示越大規模之地震將獲得較大之曲線下面積，說明越大規模地震越容易出現地震前兆。此外，門檻值p-value趨近於零，顯示電離層異常於台灣地區地震視為有效之前兆。;Receiver Operating Characteristic curve (ROC curve) be used to study seismo-ionospheric precursor (SIP) in Taiwan. A median-based method together with the z test is detected the relationship between ionospheric F2-peak plasma frequency foF2 and 50 M≥5.5 earthquakes, local GPS TEC (Total Electron Content) and 50 M≥5.5 earthquakes 1994-1999, and GIM (Global Ionospheric Map) TEC 129 M≥5.5 earthquakes 1999-2014 in Taiwan. First, it is calculated that move 15-day median, upper quartile and lower quartile for create the reference range of upper bound and lower bound. The anomalies are two result that increase (positive) anomaly and decrease (negative) anomaly. In total, z-test is found that 1-4 days and 23-28 days before earthquake are negative anomaly and negative anomaly, respectively. In detail, the results of foF2 show that negative anomaly is in period of 1200-2000 LT 1-3 days before earthquake 1994-1999. However, GPS TEC shows that negative anomaly is in 1400-1600 LT 2-4 days before earthquake 1994-1999, and GIM TEC shows that negative anomaly is in 1800-2200 LT 1-3 days before earthquake 1999-2014. For positive anomaly, foF2 shows that increase in 1300-1500 LT 15-17 days, GPS TEC increase in 1200-1400 LT 24-28 days, and GIM increase in 0900-1400 LT 23-28 days. Further, different reference days (7, 15, and 30 days before and after earthquake) find that 30-days period of positive and negative anomaly. ROC curve shows that SIP is confirmed since the area under the ROC curve is positively associated with the earthquake magnitude. In addition, p-value are approximately zero mean that SIPs are effective in Taiwan. |
