a) The AIA field-of-view in 171 Å, displaying the active region AR11227 and the flare epicenter. b)−d) Running difference images illustrate the QPF wave trains. The wavefronts of three distinct wave trains are marked by arrow groups in varied colors. The solid lines (L1-L5) forming a fan geometry are the cuts used in making time-distance arrays. The dashed arcs are concentric at the flare epicenter, the radii are 100 Mm, 200 Mm and 300 Mm, respectively.