The seismographic stations deployed as part of USArray are one component of the U. S. National Science Foundation-funded major research equipment facility EarthScope. When fully operational, USArray will include 400 broadband stations in a Transportable Array (TA) that will be deployed over a regular grid of sites with approximately 70 kilometer spacing. The TA will migrate across the United States over the next decade, ultimately occupying about 2000 sites in the conterminous United States and Alaska.