This article explores the suitability of a Wii nunchuk based USB accelerometer as an earthquake sensor for the Quake-Catcher Network (QCN) project. It examines the nunchuk over several metrics: precision and range, frequency response, total cost and availability.
Using a Wii Nunchuk as an earthquake sensor - [Link]
The USGS maintains a server online that consolidates all the seismic data received from sensors all around the world. Terremoto uses an LPC Expresso board and an XPORT AR ethernet module to query the USGS server for a list of earthquake activity. When a new earthquake is received by Terremoto, tones are generated that correlate with the magnitude of the earthquake.
Terremoto – Earthquake Sounder based on the 555 Timer – [Link]
this DIY project you can record earthquakes from around the world. This is a well-documented build, but you will have to purchase some software to interface with your seismometer. This site is a good place to start your amateur seismology and research. [via]
The following papers contain descriptions of a seismometer sensitive enough to detect and record earthquakes from around the world. It can be built using readily available parts from your local hardware store and from any general- purpose mail-order electronics supplier.
Build Your Own Seismometer - [Link]