澎湖群島位在臺灣海峽，處於歐亞板塊東南邊緣的淺水區（< 100米深）。以前在此區的地球物理研究主要以整個臺灣海峽為主體，較少有以澎湖為目標的分析。因此這次的研究，將要利用噪訊成像反演澎湖群島的淺層剪力波速度構造。本研究於2015年5月至2015年6月在澎湖及其周圍佈放了125個單分量短週期的Texan儀器，從測站對的連續紀錄中重建兩測站之間的雷利波經驗格林函數，並使用多重濾波法以及影像轉換技術得到群速度以及相速度頻散曲線，相速度可信賴週期大約落在0.6-4.6秒，最後以相速度頻散曲線，反演波線的一維平均速度分佈得出剪力波速度構造。從速度構造結果顯示在西嶼、白沙島及澎湖本島和島嶼間的海灣，在短週期中島嶼速度相對較快，海灣速度相對較慢；在長週期中島嶼的速度則是相對較慢，而海灣則相對較快，反應出此區深部可能有受到火成岩的影響。;The Penghu Islands are located on the southeastern edge of the Eurasian plate in the Taiwan Strait. Previous geophysical studies mainly focused on the entire Taiwan Strait, but did not only target to the Penghu Islands as a research area. However, there are some geological variations in the Penghu Islands deserved for more detailed studies. In this study, I will use ambient noise to invert the shear wave velocity structure in the Penghu Islands for the first time. We deployed 125 Texan instruments from May to June 2015. The Rayleigh wave empirical Green′s function between the two stations is reconstructed from the continuous record of the station pair, and the group velocity and the phase velocity dispersion curve are obtained by using the multiple filter technique and the image transformation technique. Finally, the phase velocity dispersion curve is used to invert the one-dimensional average velocity distribution of the ray path in order to obtain the shear wave velocity structure. As a result, for the short periods of the phase velocities, the velocities beneath the islands (Siyu, Baisha Islands and Penghu Isles) show relatively faster than those beneath the bay areas. However, it is interesting to note that for the long periods of the phase velocities, the velocities beneath the islands are slower than those beneath the bay areas. Based on the well logs and the distribution of magnetic anomalies, the higher velocities beneath the bay areas could be related to the intrusive igneous rocks.
