I gave an ungraded pre-test before class to help you recall as much as you could about the concepts that we will discuss this class and next. Studies show that you will retain material better if you first struggle with problems (or questions) before you are shown “answers”.  Learning is more deep and meaningful when there is some struggle to recall.

• What is stress?
• What is strain?
• What is a tensor?
• What is Newton’s 2nd Law?
• What is a wave?
• What is the wave equation?

Any serious earthquake-science graduate student should be able to answer these questions. If you couldn’t it only means you should probably discuss the material more often – everyone forgets. Reinforcing understanding through discussion is an important reason universities work, they are places where such discussions occur naturally. Talk to each other about your work. Practice explaining things.