Seismometer (Greek: seismos: earthquakes and metero: measure) is a tool or a vibration sensor, which is usually used to detect earthquakes or vibrations in the ground. Recordings of this instrument called a seismogram.

Prototypes of this device was first introduced in 132 BC by the Han Dynasty mathematician named Chang Heng. With this tool one can determine the future direction of where earthquakes occur.
With today’s technological developments, the ability of seismometers can be improved, so that it can record vibrations in the frequency range is quite wide. The tool is called broadband seismometers.

Seismograph is a device that measures and records earthquakes. In principle, the seismograph consists of a weight hanger and a pointed tip like a pencil. That way, it can be seen through the strength and direction of seismic motion picture of the earth as recorded in the form of seismograms.

The working principle

Seismograph has a sensitive instrument that detects seismic waves generated by earthquakes. Seismic waves that occur during an earthquake depicted as wavy lines on a seismogram. Seismologist measure these lines and calculate the magnitude of the earthquake.
Previously, only seismographs can detect horizontal movement, but this time the seismograph was able to record the movements of the vertical and lateral.

Seismograph using two mechanical movements and electromagnetic seismographer. Both types of mechanical motion can be detected both vertical movement and horizontal movement of the tools used depending whether vertical or horizontal.
Modern seismographs use electromagnetic seismographer to move volatility pull wire system to a magnetic field. Events that give rise to vibration is then detected through spejlgalvanometer. seismograph


In the mid-18th century, an earthquake is measured with an instrument called seismokop. Seismokop earthquake recording equipment is the most primitive. Seismokop consists of a simple container containing water or mercury. When an earthquake happens, the fluid will move up and down due to earthquake vibrations.

Major breakthrough for the measurement of earthquake came in 1920, when two American scientists developed a device called a Wood-Anderson seismograph. This tool is more sensitive than existing seismograph at the time, so immediately widely used around the world and became the forerunner of seismographs that now exists and develops. Currently, the seismographs used by Seismologist in studying faults and earthquakes.

Classification of Earthquake Measurement

Seismograph using two different classifications to measure seismic waves generated earthquakes, earthquake magnitude and intensity of the earthquake. The second classification of these measurements using different measurement scales. Measurement scale of the earthquake on the Richter Scale and Mercalli Scale. Richter scale used to describe the magnitude of the earthquake while the Mercalli Scale is used to indicate the intensity of an earthquake, or the influence of earthquakes on land, buildings, and people.

Classification of Magnitude Earthquake

In 1935, an American Geophysics named Charles Francis Richter (1900-1985) along with another Geophysics named Beno Gutenberg (1889-1960) developed a scale which in principle can compare all the seismograms to get a picture of a similar strength tremors. The scale is named on the Richter Scale and up to now recognized as a common standard magnitude scale.

Designed with the logarithmic Richter scale, which means that each step shows the strength that is 10 times more powerful than its predecessor. 5 on the Richter Scale indicates the crunch, that is 10 times stronger than the one at 4 and 100 times stronger than one in three on the Richter Scale. This calculation is often referred to as the Richter Scale is open, because it operates without any upper limit.

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