震天 is a verb-object compound literally meaning 'shake the heavens', used to describe an extremely loud, resounding noise — deafening, earth-shattering. You can use it as a predicate (e.g. 鼓声震天 'the drumming shakes the heavens') or as a modifier (e.g. 震天的响声 'a deafening noise'). It carries a vivid, exaggerated tone typical of literary or dramatic contexts.