|摘要: ||地震工程學家常以最大地表加速度(Peak Ground Acceleration)來估計可能的震災，但最大地表加速度只能代表作用時間極短的(最大)地震力，且一般而言，組成最大地表加速度的地震動成份(Components)的振動頻率較高，對於結構簡單且自然振動頻率較高的低矮建築物影響較大，以今日複雜的結構物環境，很難只用最大地表加速度來推估可能的震災。譜震度(Spectral Intensity)包含地震延時、振幅和頻率內涵等與震災相關的種種特性，因此更適合做為評估地震災害的指標。在工程應用上，地震危害度裡衰減關係的發展對地震災害減災是一個很有用的方法。由於地震引起的地表震動主要受到震源錯動過程(Source Rupture Process)，震波傳遞路徑(Propagation Path)，以及場址地下地質(Site Gelogy)的影響，因而震度衰減律公式(Attenuation Equation)應包含能表現這三者的性質之參數。常用的震度衰減律公式僅以一個簡單的規模代表震源效應，事實上，震源錯動過程相當複雜，其對震度的影響絕不是一個規模參數可以表達出來。場址效應則另以統計方法求得修飾的參數來補償。基於在譜震度的研究基礎，本計畫的目標將探討場址地質對譜震度的效應。由於場址效應與頻率有關，因此我們將分區(依地質分區)探討不同頻率或頻寬之場址效應，最後將應用求得的譜震度預估模式從事實際的地震危害度評估作業。|
Nowadays, the structural environment is becoming so complicated that the originally defined intensity scale and PGA are not adequate to do a good job for assessing earthquake damage. Therefore, an index adequately assess earthquake damage is needed. Spectrum intensity (SI) includes the three elements affecting earthquake damage, earthquake duration, frequency content, and amplitude, and it is a more adequate intensity parameter to assessing earthquake damage. The development of an attenuation relationship is very important in seismic hazard analysis for earthquake hazard mitigation. The vibration of the earth surface caused by an earthquake is affected by many factors, such as the characteristics of seismic source, the attenuation of seismic waves from the seismic source to a recording site, and the soil condition at the recording site. Therefore, parameters in intensity attenuation formula should contain these factors. For simplicity, the commonly used intensity attenuation formula at present only includes two parameters, magnitude and distance. The commonly used intensity attenuation formula represents source effect simply by magnitude. In fact, source effect includes the geometric countenance of the source, source mechanism, and the slip process of the source and slip distribution. Source effect has a very complicated influence on earthquake intensity and absolutely can not be simply represented by a parameter, magnitude. Site effect is compensated by modified parameters computed by statistics method. Based on the research results of spectrum intensity, the objective of this project focuses on exploring the site effect of spectrum intensity. Since site effect is related to frequency, site effect of different frequencies in different areas (classified according to geology) will be investigated. Finally, the prediction model of spectrum intensity will apply to seismic hazard assessment.