Check out "The Scientific American Book Of Projects For The Amateur Scientist" - C. L. Strong describes quite a bit of this in the section "The earth sciences". The schematics date from 1960 (tubes, not transistors) but you'll find updates around the web.

http://www.sciencemadness.org/library/books/projects_for_the...

The basics of detecting lightning is to measure the potential difference (voltage) between the earth and the air. A simple home experiment you can do to detect it is to create Franklin bells:

http://en.wikipedia.org/wiki/Franklin_bells

http://www.instructables.com/id/Franklins-Bells/

In the case of this, instead of the higher voltage being in the sky (hence why lightning discharges down), the higher voltage is in the earth. You can measure the voltage between the bells (multimeters usually only go up to a few hundred volts, so wouldn't be enough) at various locations across a large area, and see if any anomalies come up before an earthquake :) You might get annoyed by the ringing first though...