| 摘要: | 地下核子試爆是為地球上最大的人造震源,其強烈地表錯動之垂直震 盪,足以引發地表附近大氣共振,並以聲波或重力波(Acoustic and/or gravity wave, AGW)的形式行經中高層大氣,傳至電離層並帶動其中帶電粒子, 形成移行電離層擾亂(Traveling Ionospheric Disturbances, TIDs)現象。本論 文分析 2009 年 5 月 25 日北韓地下核子試爆期間,南韓、臺灣以及日本全 球定位系統(Global Positioning System, GPS)地面接收機記錄之全電子含 量(Total Electron Content; TEC)。叢集分析用以認知並偵測該核爆引發之 TID。時間延遲法顯示引發之 TID 具有兩種模(mode),分別以 766 m/s 及 365 m/s 的速率傳播。圓圈法、射線追蹤法及波束聚集法計算 TID 之傳遞 速率為 734-766 m/s 及 323-383 m/s,與時間延遲法的結果相近,而其所 推估之核子試爆地點亦與反核試驗組織公布的位置相近(相差 40-228 km), 此二相近顯示該 TID 是由北韓地下核子試爆所引起。;An underground nuclear test, the largest artificial quake source on the Earth, can cause severe vertical motions on the ground, resonate the atmosphere near the Earth’s surface, which activate acoustic and/or gravity waves (AGW) traveling through the middle/upper atmospheric and then into the ionosphere, where disturb the electron density within it and result in traveling ionosphere disturbances (TIDs). This MS thesis research work studies the total electron content (TEC) derived from measurement recorded by the ground GPS receivers in South Korean, Japan and Taiwan during the underground nuclear test on 25 May 2009. The cluster analysis is used to identify and detect TIDs induced by the underground nuclear test. The time delay method shows that the induced TIDs have dual modes traveling with propagation speeds of 766 m/s and 365 m/s. The circle method, ray-tracing technique and beam-forming technique are further applied to compute the propagation speed and to locate the source of the detected TIDs. The computed propagation speeds of 734-766 and 323-383 m/s are close to that estimated by the time delay method, while the source locations are nearby the one reported by CTBTO (Comprehensive Nuclear-Test-Ban Treaty Organization) about 40-228 km. The agreements strongly suggest that the observed TIDs are triggered by the North Korean underground nuclear test. |
