由波譜強度評估地盤工程特性的可行性研究

A STUDY OF THE FEASIBILITY OF ENGINEERING CHARACTERISTICS OF SOIL USING SPECTRUM INTENSITY

本文應用921集集地震與1022嘉義地震等強震數據分析波譜強度SI在台灣地區的分佈情形，並探討將地震數據先依尖峰加速度（PGA）比例作正規化後再用以計算波譜強度、研究以此修正後之波譜強度作為地盤工程特性之指標的可行性。本文繪出台灣地區的波譜強度等值線，並比較其修正前、修正後的等值線形。研究成果發現修正後的波譜強度等值線的峰值區並非位於震央附近，而中央山脈一帶的修正後波譜強度較低，沿海地區的修正後波譜強度較高。由於波譜強度的定義原為地震波對不同頻率、阻尼之結構系統的危害度指標，所以應用正規化後的地震波所求得之修正後波譜強度應具有作為地盤工程特性指標的意義。

Applying the data collected from the 921 Chi-Chi Earthquake and the 1022 Chia-Yi Earthquake, this paper studies the distribution of spectra intensity (SI) in Taiwan and the feasibility of normalized spectra intensity using scaled data from peak ground acceleration, and applies normalized spectra intensity as an engineering characteristic index of soil. The paper presents the contour map of SI before and after SI is normalized. The results show the peak area of normalized SI is not at the epicenter while the central mountain area usually is a lower value area while a seashore area is a higher value area, due to SI being defined as a risk index for structures with different frequency or damping. The mean of the SI computed from normalized seismic waveform should show the engineering characteristics of any soil at question.