EarthScope uses a wide variety of instrument types to conduct research. The Plate Boundary Observatory has 1100 permanent GPS stations, 78 borehole seismometers, 74 borehole strainmeters, 28 shallow borehole tiltmeters and 6 long-baseline strainmeters. USArray has 400 transportable seismic stations that will occupy 2000 sites. The Flexible array has 2146 seismometers available for use in temporary experiments. The Reference Network has 118 permanent seismic stations. The Magnetotelluric Array has 27 magnetic and electric field detectors. SAFOD has instruments installed in an active part of the San Andreas Fault.