With 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.

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

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SeisMac – Turn your Macbook into a seismograph – Link