The USArray component of the NSF-funded EarthScope project ended its observational period in September 2021 and all remaining close-out tasks concluded in March 2022. Hundreds of seismic stations were transferred to other operators and continue to collect scientific observations. This USArray.org website is now in an archival state and will no longer be updated. To learn more about this project and the science it continues to enable, please view publications here: http://usarray.org/researchers/pubs and citations of the Transportable Array network DOI 10.7914/SN/TA.

To further advance geophysics support for the geophysics community, UNAVCO and IRIS are merging. The merged organization will be called EarthScope Consortium. As our science becomes more convergent, there is benefit to examining how we can support research and education as a single organization to conduct and advance cutting-edge geophysics. See our Joining Forces website for more information. The site earthscope.org will soon host the new EarthScope Consortium website.

USArray
A Continental-scale Seismic Observatory

Sensors

A seismometer is a very sensitive instrument that can detect movements of Earth's surface. The surface is in constant motion due to natural and man-made phenomena. For example, the solid Earth tide is caused by the gravitational pull of the moon stretching Earth. Tucson slowly rises and falls twice a day about 40 cm due to the moon orbiting overhead. Mining explosions are a source of seismic energy. Ambient seismic noise amplitude is measured in nanometers, and can have a frequency bandwidth from 10s of Hz to days.

Very-Broadband Seismometer

Streckeisen STS-1

  • Flat to velocity 0.0028 - 10 Hz
  • Dynamic range > 140 dB
  • Requires extensive vault facilities
  • 3-orthogonal components, 24-bit digitized at 40 Hz
     

Broadband Seismometer

Streckeisen STS-2 and Guralp CMG-3T

  • Flat to velocity 0.01 to 50 Hz
  • Dynamic range > 140 dB
  • Requires simple concrete pad with thermal insulation
  • 3-orthogonal components, 24-bit digitized at 40 Hz
     
 

Teledyne-Geotech KS54000

  • Flat to velocity 0.003 - 16 Hz
  • Dynamic range > 140 dB
  • Emplaced in 8" borehole, at a depth of 100m
  • 3-orthogonal components, 24-bit digitized at 40 Hz
     
 

Short-Period Seismometer

Guralp CMG 40T-1Hz

  • Flat to velocity 1s - 100 Hz response
  • Dynamic range > 90 db
  • 2000 V/m/s sensitivity
  • Output 20 V peak-to-peak
  • No mass locking required
  • Power consumption = 38 Ma at 12 V DC
  • Weight = 2.49 Kg
  • Case diameter = 154 mm
  • Case height = 207 mm
  • Operating Temperature = -10 to + 75 deg C
  • Manufacturer link
     

High-Frequency Seismometer

 

Geospace GS11D

  • Natural Frequency 4.5 Hz
  • Coil resistance = 380 Ohms
  • Sensitivity = 0.32 V/cm/sec
  • Damping with 380 Ohm coil = 762
  • Moving mass = 23.6 g
  • Height = 3.35 cm
  • Diameter = 3.18 cm
  • Weight = 111 g
  • Manufacturer link
     

Strong-Motion Sensor

Kinemetrics Episensor ES-T

  • Dynamic Range > 155 Db
  • Bandwidth DC to 200 Hz
  • User selectable full-scale range +- 0.25 g, +-0.5 g, =+-1 g, +-2 g, or +-4 g
  • Power consumption = 35 mA (Low Noise aAmp) @ 12 V DC
  • Operating Temperature = -20 deg C to 70 deg C
  • Physical size = 13.3 cm; diameter = 6.2 cm height