Today I checked the recordings for my DIY magnetometer (yup, that’s “magnetometer” and not “seismometer”; keep reading) and found that it managed to detect the Mag 7.7 earthquake offshore of British Columbia. That’s about 1200 miles away! Not bad for a device that’s not even intended to record earthquakes, 🙂

The  magnetometer is of torsion design with free hanging mirror. This makes is susceptible not only to magnetic fields but also to very slight vibrations. While this might be considered a drawback in a magnetometer, I enjoy being able to detect far away earthquakes.

Because of the way the mirror is attached, the device is very sensitive to horizontal vibrations and has limited sensitivity to vertical vibrations. This is the reason why the P-wave, which is mostly vertical, is barely detectable.