Earthquakes have been in the news a lot this year, from thee earthquake in Japan to the surprising quake in Virginia, to quakes in Oklahoma caused quite possibly by fraking, earthquakes have been on the brain. We often discuss the possible ways animals may help us predict earthquakes, or the science behind trying to predict the when and where through gadgets. That is still a ways off, but in the mean time, there are warning systems that can help you stay alert -- and there's at least one you can make yourself.
Instructable user Andrewblog came up with a design for an earthquake sensor. Andrewblog states, "When an earthquake hits a primary wave and a destructive wave travel through the earth surface. The primary wave is faster, but causes a small tremor that we can not feel. An high sensitive earthquake detector feels the small tremor some seconds before the big earthquake, and puts out a sound alarm. The time advantage depends on the distance from the epicenter."
The video shows the schematic for the device, and an example of the device working:
And there are more detailed instructions for creating the alarm over on MAKE.
"That device consists of an high sensitive lever, which is hooked to a spring. A weight is fixed at the end of the lever by a M8 screw (the lever should work with a frequency of about 2 HZ). When the sensor shakes, a M3 screw fixed on the lever will touch the horizontal spring, and it will close a delay off circuit which drives a piezoelectric bell."
The problem with this device is how to keep it from detecting footfalls or other non-earthquake-y shakes that trigger the alarm. It might need to be set up in a location that isn't overly sensitive to every minute movement (but that might also defeat the purpose). It is still a very interesting project, and considering where one lives, it might also be an important one.