This induces a small voltage in the wire coil.  These devices have been used for decades by oil and gas companies to conduct surveys of underground rock and strata, using induced seismic shocks. Although millions of them have been manufactured over the years they are often hard to find.  You can make your own geophone by suspending a strong magnet with a rubber band, so it hangs inside a coil of wire containing several hundred turns. Any vertical movement will produce a detectable voltage in the coil.  To reduce false signals produced by air movements, I suggest that the assembly be housed inside a pipe or some other container.