You have probably heard all about the Japan Earthquake Early Warning System system. If not, the prior link has a great article on the subject. Unfortunately, the United States has nothing like this. It might be coming soon, but in the meantime, we are all flying blind here.
After the Japanese earthquake, I begin to look around for some equipment to do the same. I first turned to a company called Seismic Warning Systems, who has yet to return any of my inquires to purchase hardware. So, I had to set my sights a little lower for the commonly available Quake Alarm. After connecting it to an Arduino, writing a python script, and scanning for the first sign of a P-Wave, and filtering out local vibrations, I am proud to say that we have not seen one false positive! We have not had an earthquake to test with, but after simulating a P-Wave by slowly oscillating an exterior wall, I am quite certain that it will work just fine.
Originally, the system used an iPhone app to push notifications at the moment a quake was detected. It turns out, the Apple notification system has very, very low latency, ranging from 0 to 2 seconds (Up to 2 seconds if the device display is off in standby mode). I wrote a nice little app to provide notifications, but this proved to be not ideal. First, I would have to deal with the AppStore approval and maintenance of an application, and second, I would be leaving out a chunk of users.
The system I have put online uses traditional SMS notifications through an SMS aggregator I use. The delay is usually very low, so its a close second to iPhone alerts. I have had a few folks on this system testing it, and I think I am ready to open this up for anyone else interested.
If you want quake early warnings, visit this link to sign up.
Note that this thing isn’t going to go off with one of those little quakes, but you may see notifications on 5.0 and larger. You know, the ones you might want a little warning before hand.
Since I only have one sensor (anyone else want to put one up?), I cannot provide estimated arrival time, intensity, and likelyhood of advance notice. If the quake happens close to you, but far from my sensor, you may not see any advanced warning.
UPDATE Oct 17, 2011: Software and hardware guide now on GitHub! https://github.com/spaceneedle/P-Wave-Detector