In this post I am not talking about the chopped audio method used in all my previous devices. This one is just straight audio – directly into the PC’s sound card.
Some time ago I had bought into the idea that “you can’t record earthquakes through a PC’s sound card because they don’t respond to low frequencies,” in fact I had repeated it myself. But recently I’ve found that this is not strictly true. Very long period waves from distant quakes will certainly not register much through a sound card, but quite good results can be obtained with local quakes and P waves from strong, distant quakes. (The trace in the above photo shows P waves from a 7.3 quake in Japan, a little left of center. Ignore the other stuff to the right of it; that’s “student quakes”.)