Wow, I can’t believe someone picked that out already!

You’re absolutely right. In storyboarding, you use a lot of different methods to indicate camera movement. Camera shakes are indicated by those square corner markings.

People draw them slightly differently depending on the show’s specifications for what’s acceptable, but generally sets of vertical lines imply a horizontal shake, horizontal lines imply a vertical shake, and corner markings imply mixed shake. The camera is moved fractionally up, down, left and right, usually on a frame by frame basis, to create an earthquake or impact effect. You see it very often in cartoons when people get hit over the head or slam into walls etc.