Difference between 惊讶 and 吃惊？
yes, there is a way to tell the two apart. 


惊讶 is mostly used as an adjective, like 惊讶的表情 which means 'a surprising face look'. 
吃惊 is used as the same as 'be surprised', for example 我吃了一惊 which means 'I was surprised'.