A seismograph is a scientific instrument which lists information about the duration, intensity, and direction of a seismic disturbance. In addition to marking earthquakes, seismographs can also track large explosions, tidal waves, and other events which cause the ground to shake. These devices are used to gather more information about seismic disturbances, and to monitor the earth for early warning signs of seismic events. The Richter scale is used to measure the magnitude of earthquakes. The scale is numbered from 0 – 10. It is a logarithmic scale, meaning each unit of increase on the scale corresponds to an absolute increase by an order of magnitude, or factor of 10. Earthquakes measured at less than about 2 on the Richter scale are not very dangerous, and can barely be measured, much less felt. An earthquake is usually considered much more serious once it hits about 5. At magnitudes of 7.0 or 8.0 the damage can be disastrous.
New Zealand Seismographs
