All that came to my mind is making sure to physically bond it to the floor. But then you still need to have something that moves relative to the magnet and then

All that came to my mind is making sure to physically bond it to the floor. But then you still need to have something that moves relative to the magnet and then I got confused again. What do seismographs do? People also use acoustic pings to measure soil and rock density underground. What are those devices using for their “microphone”? And yeah, would an accelerometer work? I don’t know what the temporal resolution is on your standard Amazon / AliExpress accelerometer is but it’s probably pretty decent?