Key USArray facilities include the Transportable Array of seismometers and atmospheric sensors, which was deployed progressively across the 48 contiguous states and is now moving to Alaska, and the pool of portable seismometers in the Flexible Array. They directly permit acquisition of the requisite seismic data for imaging subsurface structure at multiple scales and for studying earthquakes in many environments. USArray also consists of permanent broadband seismic stations—Reference Network—that provide a large-aperture, fixed grid of observing sites essential for tying together the 70-km-spaced grid of sequential Transportable Array deployments. Data acquired by USArray’s Magnetotelluric Facility supplement the seismic data by providing images of crustal and lithospheric conductivity structure. Transportable Array and Reference Network station distribution together provide unprecedented spatial coverage and uniformity of seismic wavefield sampling, enabling well-established and new seismological analyses to reveal deep Earth structure and to characterize earthquake sources throughout the continent. The scientific community is able to conduct a host of research projects with Transportable Array data and with separately funded field deployments of Flexible Array sensors.
Station L44A in Lake County Forest Preserve, IL