3d model for visualizing earthquake focal mechanisms

Tuesday 1:30pm-2:40pm CC Building Circadian
Share-a-thon Part of Tuesday


Joann Stock, California Institute of Technology


I will bring several sets of these models and some whiteboard markers so the participants can try it for themselves.


Students use a transparent hemisphere and a rigid inset of two perpendicular planes. The inset represents the earthquake fault plane and auxiliary plane. The students use erasable whiteboard markers to trace the intersections of the planes with the lower hemisphere. Then they remove the inset and look down on the transparent hemisphere to see how the fault plane traces appear from above. They can then draw this 3D perspective on a sheet of paper to show what the focal mechanism looks like.


I use this in a freshman class and in a graduate class when discussing earthquakes. It allows the students to easily visualize what is represented by an earthquake focal mechanism.

Why It Works

The marks traced onto the transparent atmosphere hemisphere are completely erasable so the student can experiment with focal mechanisms and faults of different orientations. They can then erase their work and let the next student try it. This is innovative because the transparent hemispheres can be easily purchased from a craft store. The rigid fault inset is made from 2 pieces on a 3D printer.