Using SeisMac to Turn Your Laptop into a Seismograph for Teaching

Abstract

You probably are familiar with the situation. You're trying to explain the arrival of seismic waves to your class. Or maybe it is your spouse (or child, grandparent, parole officer, whatever). You are excited and enthusiastic, talking about frequencies and wavelengths, dispersion, Hilbert transforms, and so on, and all you get in return is blank stares. They don't get it. The problem is that you are showing them a static black-and-white image of squiggly lines, and you just can't get them to see the dynamic motions and transfers of energy involved. You wish you had an actual seismometer to whip out and use to demonstrate your points. Well, your wish has been granted! In fact, you very well may have access to it already. SeisMac is a free Mac OS X application that runs on a MacBook or MacBook Pro and turns built-in accelerometers into a three-component seismograph. These Mac laptops are installed with a sudden-motion sensor, similar to automobile air-bag accelerometers, that is designed to lock up your hard drive if your laptop falls to the ground. It works. Trust us (or, rather, trust the dents in our laptops). Early on, Mac users discovered this feature and were using it to do things like turn their laptops into Star Wars light sabers (complete with sound effects). However, freelance programmer Daniel Griscom realized the potential and created SeisMac (which he wrote about in Electronic Seismologist for SRL volume 77, issue 6 (November/December 2006) pp. 731–733). With some seed funding and guidance from the Incorporated Research Institutions for Seismology (IRIS), SeisMac was honed into a real seismograph. Yes, of course, you could achieve the same results by purchasing a separate three-component accelerometer and developing a graphical user interface (GUI) that could display the signal in a user-friendly manner. But most likely, …