近期國外的研究指出，隱沒帶地震與淺部地殼地震的強地動衰減情況頗不相同，而強地動衰減式是進行地震危害度分析時必要的，且對結果極為敏感的一項數學式，故須針對台灣的隱沒帶地震進行研究。一個合適的衰減式不僅可以瞭解一地區的強地動衰減特性，並可以用來預估特定工址的強地動值，提供工程耐震設計之用。本研究使用中央氣象局自由場強地動觀測網計畫(TSMIP)及中央研究院地球科學研究所SMART1陣列所蒐集之台灣東北部地區隱沒帶板塊介面型及板塊內部型地震的強震資料，來建立最大加速度及反應譜加速度衰減式。考慮台灣東北部地區的隱沒帶地震缺少大規模、近場及遠場資料，因此本研究又選取部分國外大規模近場及遠場隱沒帶地震資料合併做強地動衰減式之迴歸分析。分析過程中，將板塊介面型地震與板塊內部型地震及堅硬地盤與軟弱地盤的強地動衰減式分開考慮，並採用了震矩規模及震源距離來進行迴歸分析。衰減模式採用Crouse (1991)所提出之隱沒帶地震地動衰減模式，迴歸技巧採用區塊登山法來搜尋誤差平方和達最小值時之各項參數。分別獲得能代表兩類地盤及兩型震源的最大水平加速度與反應譜加速度衰減式。此衰減式所推估之強地動值較過去淺地殼地震地動衰減式為高，但仍然略低於國外隱沒帶地震強地動衰減式的推估值。 Recent study revealed that the attenuation of strong ground-motion is different between subduction zone earthquakes and shallow crustal earthquakes. A strong ground-motion attenuation equation is essential and influential for seismic hazard analysis. Therefore, we need to study the strong ground-motion attenuation relationship for subduction zone earthquakes in Taiwan. A suitable attenuation equation can express the characteristics of the strong ground-motion attenuation for a region, and can be used to predict the ground-motion value of a specific site for seismic resistance design. In this study, strong ground-motion data of subduction zone both interface and intraslab earthquakes from TSMIP and SMART1 array in northeastern Taiwan were used to establish PGA and SA attenuation equation. Considering the lack of higher magnitude, near field, and far field data of the subduction zone earthquakes in northeastern Taiwan, some globle subduction zone earthquake data were included for regression analysis of the attenuation equation. In the process of regression, strong ground-motion attenuation equations for interface, intraslab earthquakes were analysed, so as rock site and soil site. Moment magnitude and hypocentral distance were used in developing the attenuation equation. The attenuation form for subduction zone earthquakes proposed by Crouse (Crouse, 1991) was adopted in the analysis. Block hill-climbing algorithm were used to search the coefficient of the attenuation form that minimize the sum of squares of deviations. The resultant PGA and SA attenuation equations include two site class types and two earthquake source types. The ground-motion value predicted by this attenuation equation is higher than crustal earthquakes attenuation equation which usually used in Taiwan, but is lower than that predicted by the equation for worldwide subduction zone earthquakes.
