As rock interface are crossed, the elastic characteristics encountered (by seismic waves)generally change abruptly, which causes part of the energy to be reflected back to the surface, where it is recorded by seismic instruments. (4)
当岩石界面被穿过的时候，震波所遇到的弹性性质通常会发生突然的变化，这就使得一部分能量被反射回地面，在地面反射回来的波被震波纪录仪记录下来。
难句类型：复杂修饰、省略、过去分词与谓语易混
解释：绝大多数人读到the elastic characteristics encountered generally change abruptly这一句的时候，第一反应都是把encountered看成了谓语动词，再看到change abruptly的时候又搞不苾怎么会跑出来两个动词，反复看上n遍才看清楚这句话的结构。本句难就难在主语the elastic characteristics后面的表示袪的过去分词encountered的动作发出者在句子中根本就没有出现过，相当于原文在encountered后面省略了一个by seismic waves,倡读者却没有心理准备，同时也不熟悉这种分词修饰的方式，因此也难以读懂。
意群训练：As rock interface are crossed, the elastic characteristics encountered (by seismic waves)generally change abruptly, which causes part of the energy to be reflected back to the surface, where it is recorded by seismic instruments.
