Seismograph

• A seismograph is one of the best known geophysical instruments. A seismograph allows scientists to study the movement of the earth's crust. This instrument measures the direction, duration and intensity of movements of the earth's crust. A seismograph is favored over a simple seismometer because a seismograph combines the detection capabilities of a seismometer with a permanent recording device. This allows scientists to efficiently study earthquakes and any other fluctuations in the earth's crust.
  
  

Magnetometer

• Scientists use a magnetometer to study the earth's magnetic field. This device can measure the strength and direction of a given magnetic field. Two main types of magnetometers are used: scalar magnetometers and vector magnetometers. Scalar magnetometers measure the strength of a magnetic field; vector magnetometers record the direction of a magnetic field. Magnetometers are used in conducting geophysical surveys and locating iron deposits, ship wrecks, buried objects and archeological sites.
  
  

Ground-penetrating Radar

• Ground-penetrating radar is a system used by scientists to map the interior of the earth. This method takes two-dimensional cross-sections of the earth's subsurface features. The process requires aiming a radar signal at the ground. Below-ground objects and layers reflect the signal. These reflections are detected by a receiver. The total time it takes for the signal to return shows the depth of an object or area. This data can later be analyzed to create three-dimensional images.
  
  

Magnetotelluric

• Magnetotelluric devices also allow scientists to map the interior of the earth. Magnetotelluric instruments measure electrical currents within the earth. Scientists gauge the resistivity of objects to electrical currents. They then are able to calculate the makeup of the earth's interior at a specific location. For example, rocks containing fluids will generally have a low resistivity, while cold and dry rocks will show a high resistivity.