Evaluating the Efficacy of an Animation to Enhance Understanding of First Motion Diagrams

Having taught the interpretation of first motion diagrams (sometimes referred to as "beach ball diagrams" due to their appearance) in an Introduction to Physical Geology class over many semesters, I was frustrated with the hand-waving this effort entailed when describing static diagrams. I searched for a computer animation that would show how the initial ground motions in an earthquake correspond to the various shaded regions in each first motion diagram, but was not able to find such a pedagogical tool in existence. I decided to work with the staff of my University's Faculty Computing Services to create something that would serve this need. We designed and constructed an animation of strike-slip motions, which can be seen at http://people.hofstra.edu/alex_smiros/earthquake/grid_22march2011.swf. A still image of the animation appears in Figure 1. In order to see if utilizing this visualization enhanced student understanding of the difficult concepts involved in interpreting first motion diagrams, I compared scores on test questions involving first motion diagrams from two different semester iterations of the course: one was taught without utilizing the animation, and one was taught with utilization of the animation.