都會區由於人口密集高樓林立，且常位於沖積平原上，近地表土質鬆軟，容易遭受地震的破壞，若地震發生在都會區底下或近旁時，災情更是嚴重，1995 年日本板神地震及2004 年新瀉地震之「直下型地震」是為明例，因此，都會區防震要求，需有特別的思維。台灣多震，本島各角落均受到地震之威脅，都會區因常位於鬆軟的沖積平原上，尤為敏感，因此都會區是否靠近地震帶及場址震波放大，在在威脅都會區之防震安全，在台灣尤以中南部地區所受威脅最大。欲探討都會區承受地震衝擊的能力，首先需瞭解地下構造，包括構造形貌，地層特性，及震波速度（P 波及 S 波）等。瞭解地下構造，才能進一步探討地震從不同方向進來時，都會區各位置可能的反應，從而採取因應之道。本研究提議在都會區進行精細的反射震測地下構造探測，將地下構造之形貌及P 波S 波速度調查清楚，做為都會區地震相關研究之基礎。我們已建立216 波道震測儀器系統，並引進震盪震源，調查工作能順利進入都會區進行，野外施測採密間距（4m）、連續10 幾公里之測線，探測深度2 秒（約3000 公尺），將油工業震測所忽視的淺部構造，包括基盤及其上之第四紀地層、近地表沖積層，都能詳細測繪。第一年調查區域在台北盆地，第二年及第三年在埔里盆地及雲嘉地區（因測區範圍大）。第四年將進入宜蘭平原。本計畫所提為第四年。本計畫之預期成果包括：1) 測繪都會或平原區由深至淺之全面性地層及速度構造，建立震波模擬研究之基礎；2）測繪各區活動斷層之確實位置，瞭解斷層之間的相互關係﹐及再活動之可能性；3) 瞭解全區地質構造﹐推論構造演化及地震可能發生之模式。 ; The cities in Taiwan are regularly under the threat of earthquake shaking. Most cities are located in the flat plan area where soft surface layers may magnify the earthquake wave and cause damages. More severely, some earthquakes may occur directly under the city (i.e., the urban earthquake), which could cause even worse impacts. The earthquake mitigation problem for the city should be considered more carefully. The earthquake shaking simulation for the urban area is a good approach. However, detailed underground information need be provided before meaningful simulation is performed. The information includes the geologic structure, the fault, and the P and S-wave velocities. All these can be obtained using the ‘urban geophysical methods’. In this study, we propose to use the reflection seismic method to map the underground structure of the urban area. This method has been largely applied to detect the active faults in Taiwan and has been proved quite successful. A four year study is proposed to complete four areas: Taipei basin, the YingChia area, the Puli bason, and the Ilan plain. We will collect 2~4 seismic lines, each 10km long, in each aerea. The detection depth is 3000m (2 sec data). The obtained seismic profiles may provide useful layered structure and the P and S-wave velocities, which are then applicable for the seismic simulation. Basing on the established 216-channel seismic system, we also have a new IVI/EnviroVibe source. This vibrator provides a quite and powerful source which is ultimately necessary for the reflection seismic work in the populated areas and in the night time. This instrument has been proved important for the success of the project. Three objects of the project are 1) to find the layered and velocity structures, 2) to detect the fault in or near the study area, 3) to set up a geologic structure background which can be used for other related studies. ; 研究期間 9808 ~ 9907
