A Continental-scale Seismic Observatory

Magnetotelluric Array


Since 2006, the magnetotelluric (MT) component of EarthScope’s USArray has deployed instruments which measure the Earth's naturally occurring electric and magnetic fields. Its backbone array consists of seven stations (MT-BB) operated across the United States since 2008 as a reference network. In addition, each summer up to twenty portable MT systems (MT-TA) are deployed campaign-style occupying large footprints in areas of special interest as proposed by the MT community (2006-2011 in the Pacific Northwest, 2011-2013 in the Mid-Continent Rift). Each MT-TA site is occupied for approximately three-weeks with a nominal 70-km grid spacing for imaging of crustal and lithospheric conductivity structure. These data can also be integrated with other geophysical data to identify North America's thermal structure and study the significance of fluids in the crust. Data are archived with IRIS, and processed into transfer functions that are available for a significant number of EarthScope and other MT stations. The USArray MT program also provides instruments and modest support (i.e. instrument preparation and data handling) for PI-driven Flexible Array (MT-FA) studies.

The MT instruments are operated and maintained by the National Geoelectromagnetic Facility at Oregon State University under a subaward (PI Adam Schultz) from IRIS. Andy Frassetto serves as the MT program lead at IRIS. The scientific and operational goals of the MT program are overseen by members of the EarthScope community serving on the Electromagnetic Advisory Committee (EMAC), chaired by Rob Evans.

Recent News

  • With approval from NSF, six MT-BB stations (excluding the Blacksburg, VA site) have been decommissioned and converted to be used in portable deployments, bolstering the EarthScope MT instrument pool.
  • The 2014-2018 EarthScope MT Siting Plan was adopted by the EMAC. Deployments of the MT-TA through 2016 will focus in the Midwest, Southeast, and Mid-Atlantic before shifting westward in 2017.
  • The USGS deployed 22 MT stations in Florida (early 2015) and 20 stations in the Mississippi Embayment (late 2016) as a complement to the MT-TA.
  • Under a supplemental award from NSF reflecting priorities in the National Space Weather Action Plan, MT-TA stations were collected across New England in 2016-2017, completing the MT-TA along the Eastern Seaboard.
  • The EMAC, in consultation with IRIS governance and MT-program management at IRIS and OSU, has approved a change in the MT Siting Plan to instead occupy sites in the Great Plains at full spacing during the 2017-2018 field campaigns, thus bridging the two current footprints at full resolution.

Station Information

Status Map

Footprints of MT-TA (by year), MT-BB (now demobilized) and MT-FA (iMUSHMOCHA, MAGIC on-land) stations. Click to enlarge. Updated 8/3/17

Planned EarthScope MT-TA Deployment Through 2018

Existing MT-TA stations (white), USGS (yellow), and planned MT-TA sites in 2017-2018 (open circles). Click to enlarge. Updated 8/3/17