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