THE EarthScope USArray IN THE MID-CONTINENT AND EASTERN US: STATUS AND RESULTS

The EarthScope USArray program is providing unprecedented observation of geophysical targets across the continental United States through the systematic deployment of both seismic and magnetotelluric instruments. The seismic components of USArray consist of the Transportable Array (TA), the Flexible Array (FA), and the Reference Network. The TA component of USArray has now occupied over 1,100 sites from the Pacific coast to east of the Mississippi River. The TA stations include a three-component broadband seismometer and barometric pressure and infrasound sensors. TA stations are deployed in a grid-like arrangement, with 70 km separation between stations. At any given time, there are approximately 400 installed stations, occupying a ~2000 km by 800 km “footprint.” Each station is operated for two years. The FA component of USArray provides a pool of instruments, ranging from high-frequency geophones to three-component broadband sensors, which are typically deployed to investigate specific geological targets for time periods ranging from days to years. Finally, the Reference Network provides a fixed, permanent reference frame for the TA and FA, with approximately 100 broadband stations deployed across the contiguous US at roughly 300 km spacing. The magnetotelluric (MT) component of USArray consists of both a fixed reference network of 7 backbone stations, a transportable array of 20+ long-period MT instruments that are deployed campaign style, using a 70 km grid spacing, similar to the seismic TA stations. Instruments are also available to investigators for targeted, FlexArray-style studies. To-date 300 MT transportable array stations have been completed in the NW quadrant of the US, and operations are shortly commencing in the upper Midwest.

We will present the current status of USArray activities and progress to date, with special emphasis on standardized data products that are created from USArray data, including phase picks, wave-field animations, observations of the ambient noise field, and MT transfer functions. We will also provide an overview of USArray deployment plans as a means to facilitate and encourage collaborative experiments and investigations, and will discuss opportunities for the seismological education and research communities to participate in and leverage the FA and TA efforts.