Earthscope's USArray: Observations and Status

The three seismic observatory components of the USArray span up to five orders of magnitude in spatial scale, with deployment times ranging from days to years. The Transportable Array (TA) component of USArray has now occupied over 550 sites in the western United States, from the Pacific coast through the Rocky Mountains, and continues its multi-year migration towards the Atlantic coast. The three component broadband TA stations are deployed in a grid-like arrangement, with 70 km separation between stations. At any given time there are approximately 400 station sites, occupying a ~1900 km by 800 km “footprint.” Each station is operated for two years. The Flexible Array (FA) component of USArray provides a pool of instruments, ranging from high frequency geophones to three-component broadband sensors, and are typically deployed for focused geological targets at spatial scales two to four orders of magnitude less than the TA, and 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 geographical extent of USArray allows unprecedented observation of geophysical targets over a range of scales and the resultant data have fueled numerous studies. For example, the spatial extent and density of the TA deployment allows direct visualization of the wavefield. A number of standardized data products are produced from the USArray data, including phase picks, wave-field animations, and comprehensive observations of the ambient noise field. We present an overview of these products, as well as a review of the current status of USArray. We also discuss opportunities for the seismological education and research communities to participate in and leverage the FA and TA efforts.