台灣隱沒帶地震的強地動衰減式之偏差評估

Abstract

台灣落在菲律賓海板塊與歐亞大陸板塊的交界處，兩板塊以每年約8公分的速度聚合。在台灣的南方，歐亞大陸板塊隱沒到菲律賓海板塊之下；到了台灣北方，則是菲律賓海板塊隱沒到歐亞大陸板塊之下。而在這兩個板塊間相互不斷的擠壓摩擦下，台灣平均每年發生2000次的地震，其震源深度可以從很淺到幾百公里左右的深度。 利用過去的地震紀錄得出的經驗模型我們可以得到強地動預估式(GMPEs)，藉此估計一個測站受到不同地震時的地動強度。而強地動預估式考慮的因素通常有震源(source)、距離(distance)以及場址(site)的效應。本研究利用林柏伸和李錫堤教授在2008提出的強地動預估式，以及Abrahamson等人在2016所提出的強地動預估式做為模型，比較兩者在台灣隱沒帶地震時的偏差關係並進行評估。

Taiwan is located at the boundary of Philippine Sea plate and Eurasian plate. These two plates converge at a rate of 8 centimeters per year (Yu et al., 1997). To the south of Taiwan, Eurasian plate is subducting below the Philippine Sea plate; while to the, northeast, the Philippine Sea plate is subducting below the Eurasian plate. Collision of these two plates leads to significant compression and friction accumulated in the region along the boundary. On average, there are more than 2000 earthquakes annually in Taiwan. The focal depths of these earthquakes can be shallow or occurring at a depth of several hundreds of kilometers. Ground motion prediction equations (GMPEs), which are empirical models derived from past earthquake recordings, are often used to estimate ground motion intensity level at a site for an earthquake of particular magnitude. GMPEs consist of parameters that would describe the source, path and site effects. In this study, the GMPE models developed by Lin and Lee (2008) and Abrahamson et al. (2016) are reviewed. By using the subduction earthquakes from Taiwan, applicability and biases associated with these models are evaluated.