| 摘要: | 高雄市為臺灣地區的最大港都，第二大都市。近年來在高雄都會區大量的超高層建築及大眾交通建設（捷運系統、鐵路地下化工程）均已陸續動工，因此需要瞭解此地之地質條件。尤其在經歷過1999年的集集地震之後，為掌握高雄都會區在地震力作用下之地動特性，有必要進行有系統之調查研究。而剪力波速除為了解地工特性之重要參數，同時亦為研究地動特性所必需。 本研究利用六個大型微地動陣列量測求得深度三公里內淺部S波速度構造，而所求得的S波速度構造與利用懸盪式速度井測（P-S logging）所得之速度構造，其結果相當吻合。在地震減災方面，瞭解高雄屏東地區的土壤放大效應是相當重要的，本文使用三個建置完成之井下地震儀陣列及高密度的微地動量測，利用Nakamura（1989）所提出之單站頻譜比法進行場址效應之研究。經過仔細挑選後，共選取了705個微地動測點運算單站頻譜比值，並取不同頻率畫成放大倍率等值圖。高雄都會區及屏東平原在0.6?1.5Hz都呈現放大倍率高區，從2.0Hz放大高區開始往周圍丘陵區、山區移動。大於3.0Hz後，平原區則已經沒有明顯之放大倍率高區。從各站之單站頻譜比，選取其共振主頻並將其畫成主頻等值圖，高雄都會區及屏東平原其主頻約為0.6?2.0Hz，丘陵區、山區之主頻則在2.0Hz以上。而主頻之變化與沈積物之厚度有明顯之相關，比起利用工程鑽井資料所得之沈積物厚度，微地動結果可顯示出更細部之變化，充分顯現其方便性與經濟性。另外從單站頻譜比與速度構造計算其轉換函數之結果比較，Vs30常常不能反應出控制此區域主頻之沖積層厚度，使得比較之結果差異甚大。 2006年12月26號20點26分及20點34分，在屏東恆春外海相繼發生兩起芮氏規模7.0的地震，根據中央氣象局定位結果，地震震央分別位於墾丁地震站西南方38.4公里以及恆春地震站西方33.1公里。利用單站頻譜比法對KAU測站於恆春地震時進行非線性反應之探討，非線性反應區域，主要分佈在高屏沿岸地區，如屏東林邊、佳冬與新園一帶，林園靠高屏溪出海口，高雄市小港、前鎮等區，以及橋頭、彌陀與永安附近。而墾丁南灣地區於恆春地震發生時有發生土壤液化並造成一些災情，經單站頻譜比法分析後，南灣地區發生之土壤液化可能與區域地質條件有關，從觀測上也並無發現大範圍之土壤液化區域。 Kaohsiung city is the most important harbor and second large city in Taiwan. Recently, there are many high-rise buildings and public transportation system are under construction in this area. Therefore, it is very important to know the surface geological conditions for many practical reasons especially after the strikes of 1999 Chi-Chi, Taiwan earthquake. The shear wave velocity is a very important parameter in earthquake engineering problems and essential for studying earthquake characteristic. This study estimates the S-wave velocity structures from the surface to a depth of 3 km by six microtremor arrays. The shallow S-wave velocities also compare well with which get by P-S logging. To serve the purpose of earthquake hazard mitigation, it would be better to understand the soil amplification effect of the Kaohsiung-Pingtung area. We then conducted a research to study the site effects of the area, which includes analyze three installed borehole seismometer arrays, and perform very dense microtremor measurements in the study area. After carefully selection, we pick 705 records and use the H/V ratio method to get information of soil amplification. In this study, we select several frequencies to plot out the contour map for understanding the frequency responses in this area. For the 0.6 ~ 1.5 Hz, the contours show that main amplification effects occurred at the southern part of Kaohsiung area and most Pingtung plain. With the frequency increasing to 2.0 Hz, the main amplification area move from the plain area to the hill area. For the higher frequency (3.0 Hz), there are no obvious high contour areas in the plain area. We pick the dominant frequency of each record and plot out the contour map. At the plain area, the dominant frequency is about 0.6 ~ 2.0 Hz, and the hill area is great than 2.0 Hz. We found that the basement structure can explain the contour very well. Yet, the H/V dominated frequency distribution map reveals more detail features. The Vs30 can’t exactly respond the site effects in the plain area stations. On December 26, 2006 at 20:26 and 20:34, two successive earthquakes with the same magnitude 7.0 on the Richter scale occurred in the southeast Taiwan Strait near HengChun peninsula, with one epicenter approximately 38.4 km southwest of HEN station, and another is located in 33.1km west of NEN station. The H/V method is extended to identify nonlinear soil responses. From our result, we find most of the nonlinear soil response usually occurred in soft alluvial plain near shore area of Kau-Ping plain. The liquefaction site, Nanwan area, the phenomena of liquefaction was caused by the local refill soil of ground surface. |
