本研究使用多個短周期地震儀架設臨時的密集地震網，收集2020年中台灣西南部的地震資料，以及2016年美濃地震後的大量餘震資料，整合氣象局地震目錄及TAIGER的炸測數據等跨越空間與時間尺度的地震觀測資料，經過確實挑選與嚴格的篩選資料，透過有線差分法地震層析成象技術，計算出台灣西南部中尺度的精細速度模型，這個模型符合現有不同尺度的速度模型的共有特徵，在資料充足的地區，可通過水平與深度的6公里的棋盤格測試。根據新模型的定位結果，地震的群聚的現象比初始定位更加明顯，地震主要分布在$V_P$在5.2$km/s$的等值面以下，並重新演算的震源機制解，顯示出西部麓山帶以下5至10公里深的地震，主要由逆斷層與走向滑移的錯動型態，而且有區域分布上有明顯差異。藉由速度模型可以看整個研究區域的速度分布與地表地質分區有很強的相關性，北港高區的高速帶與西部鹿山帶的低速帶增厚，台南地區速度基盤最深可達15公里深，因此本研究所得的成果補足的過往觀測的尺度，並揭露出北港高區至台南盆地之間地震與波速變化特徵，這改進了大尺度速度模型對地質構造解析上的不足，對後續防災研究與盲斷層地震的調查提供更可信的基礎資料。;This study provides a moderate-scale seismic tomography for detailing the resolve of southwest Taiwan, which involves two temporal short-period dense seismic arrays from the SW Taiwan investigation project in 2020, aftershocks monitoring of the Meinong earthquake in 2016, and cooperated external catalog between 2012 and 2019 from the Central weather bureau, and four shots data in the TAIGER project. Optimized hypocenter through new model reveals several concentrated distributed events and their new focal mechanism with thrust or strike-slip in 5 to 10 km depth under the West foothill. The resolution test of the 6-kilometer cube checkerboard resumed well, which means small structures resolving is possible. Our results correspond to main velocity features such as Peikang High and Tainan Basin very well to others′ regional-scale tomography. Furthermore, the local velocity perturbations along the deformation front and faults in the west foothill suggest the opportunity to involve tomography interpretation with the existing geology and geophysical evidence. Hence, the evolving of dense seismic arrays and renewed tomography provide the chance to access more detailed structures in depth such as blind faults, which are difficult to detect in the past.
