Our system is designed to recognise 'P Waves'. These preceed the actual shaking (S Waves) and travel much faster than S waves. Our system can even send data to us before it gets damaged by a nearby quake. That data can then be used for the alerts.
Our seismic unit is a very clever little custom circuit board, the Raspberry Pi, that becomes a professional grade personal seismograph. It is probably the smallest seismograph of its caliber in existence, but don't let its size fool you - It can record earthquakes of all magnitudes, from the vanishingly small blips that are imperceptible to human senses, to the big destructive earthquakes that regularly happen around the world. As soon as the Unit is plugged in and set up, you can see, record and analyze the Earth's motion in real time! It will also be sending real-time data to us.
The Lert system has two main components.
The main sensor is a geophone, an exquisitely sensitive sensor about the size of your thumb. You can think of it as a microphone for Earth vibrations. The earth motion sensor that has been the standard in the oil exploration business for decades. As the Earth's tectonic plates move about, the Earth's brittle crust cracks and creaks. The geophone has been finely tuned to accurately measure even the smallest disturbances. The amplifier, digitizer and ARM processor all work together sending immediate data to our program.
Our plan is to set up sufficient numbers of units to cover all of New Zealand. These need to be in a grid of 50Km distances apart in rural areas and 25Km apart in areas closer to the main centres.
These are the most optimum distances from each other to enable more accurate recording of data and will help negate any false alarms.
These units will be visible through the global seismic network set up through Gempa. Click the following link to see the current units. http://www.raspberryshake.org/stationview
Data from all our Seismic Units streams continuously to the main server in Potsdam, Germany. The server analyses this information and if there is a spike in activity the data is sent to our own 'intelligent' algorithm for processing. It takes less than 2 seconds for us to get the information process and start sending an alert if needed.
If our program deems the data warrants sending an alert it checks all members phones and their location to the epi-centre. The alert is sent to these phones and based on the members location the message will display the amount of time the member has until the earthquake reaches them. Depending on our members location this timing may be between several seconds to over 60 seconds.