强震前兆: forerunner earthquakeforerunner of strong earthquake
前兆: omen; forewarning; premonition; foreshadow; forerunner 短语和例子暴风雨的前兆 warning signs [indications] of a storm; 成功的前兆 an omen of success; 地震的前兆 warning signs of an earthquake
预兆: omen; presage; sign; harbinger; foretaste; foregleam; foreshadow; a straw in the wind 短语和例子夏装的款式常常是秋装的预兆。 summer styles are often a foretaste of autumn fashion. 报界把这件事看作是两国之间即将恢复邦交的预兆。 the