台灣位於地震活動頻繁的環太平洋地震帶西側，隨時面臨地震的威脅，為了有效降低地震所帶來的災害，除了結構物本身耐震能力外，結構物底下土層在受到地震力時的反應行為也亟需了解。關於土壤動態參數，除了實驗室試驗，現場試驗為另一可用的選擇。
　　本研究即是以地震為一強大振動源，利用菁寮測站及羅東測站現場設置之井下陣列（downhole array）監測系統，在地震發生時真實地記錄土層反應。藉由參數系統識別法及希伯特-黃轉換，分別針對井下陣列監測系統所量測到的資料，反算求出土壤動態參數並加以比較。
　　整體而言，本文分析結果顯示參數識別之效果與模型階數、地震強度及兩測點之距離有關；而希伯特-黃轉換所得之結果可知地震所含之頻率成分與時間、振幅之關係，且由希伯特頻譜可察覺其低頻的放大效應。對於結構設計所需之土層共振頻率，可藉由線性非時變之系統識別方法來初步估算，若要更精確的分析，本文建議搭配時變方法一同估算，並於設計時同時考慮兩者之結果。

　　Taiwan lies to face the threaten earthquake at any time in the west of the earthquake zone of Pacific Ocean where the seismic activity is frequent. In order to reduce the damages caused by earthquake effectively, both the structure’s shaking endurance and the response behavior of soil layer during earthquake do need to be understood. To get the dynamic parameter of soils, besides testing in the laboratory, testing in situ is another available choice.
　　In this study, regarding earthquake as a strong vibration of sources, the monitoring system of the downhole array at ChingLiao and Lotung were used to record the soil layer response truly while taking place in earthquake. The data measured from monitoring system of the downhole array is used to calculate the soil dynamic parameter with the parametric system identification and Hilbert-Huang transform method.
　　The study shows that the analytic result is relevant to model order, the intensity of earthquake, the distance between receivers, and the relation among the frequency component of the earthquake, time, and amplitude in Hilbert-Huang transform result. Furthermore, the amplification of low frequency can be observed with Hilbert spectrum. The resonant frequency of soil can be estimated for structural design preliminarily by linear time-invariant system identification. For more accurate analysis, this study suggests that it should also consider the method with time-varying in the analysis.

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