Geophones use a custom msp430 capture board with input amps. This pcb has a serial link to base station which can ask for readings in batches. Current plan is capture to RAM (about 1k per channel?), then flush to eeprom. Base fetches values from RAM. A timestamp is needed at the start of each capture cycle.
Useful page about fast sampling 
Davis book points to a 17ms delay to wait for internal Vref to power up - we need to check this is done for all ADC12 inputs (incl probe code)