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Professional seismic observatories usually have instruments measuring three axes, north-south, east-west, and up-down. Seismologists generally prefer a vertical seismograph if only one instrument is available.
A professional station is sometimes mounted on bedrock with an uncracked connection to a continental plate. The best mountings may be in deep boreholes, which avoid thermal effects, ground noise and tilting from weather and tides. Amateur, or less exotic instruments are often mounted in insulated enclosures on small buried piers of unreinforced concrete. Reinforcing rods and aggregates would distort the pier as the temperature changes. A site should always be surveyed for ground noise with a temporary installation before pouring the pier and laying conduit.
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