GPS stations record their position by communicating with satellites once a day. By repeatedly measuring distances between specific points geologists can determine the movement along faults or between plates.These get process in time series plots that have a rate of movement of North, East, Vertical. There are approximately 2570 gps stationsA strainmeter is an instrument that is used by geophysicists to measure the deformation in the earth.
Linear strainmeters measure changes in distance of 2 set locations. This is done using either a solid piece of material (used for short distances) or a laser interferometer (used over a long distance). Solid material strainmeters measure changes over very small distances and are normally placed in boreholes. Strainmeters can measure deformation over frequencies from a few hz over days, months or years