Outside the buildings, rescuers stared at PET bottles containing water. If they saw water ripples, it meant that an aftershock was imminent, and they had to whistle a danger signal to tell their comrades inside the building to get out as quickly as possible.
同一時間，負責在建築外緊盯著盛水保特瓶的隊員，只要一發現有細微水紋表示餘震將起，就立刻吹哨發出危險信號，呼喚弟兄們緊急撤出。