A number of scales are used to measure earthquakes. These are broadly split into two main types. Magnitude scales and intensity scales.
Magnitude scales give an indication of the amount of energy released during an earthquake and intensity scales give an indication of the sevirity of ground shaking and resultant damage in a given location.
For more information on these, please see the related questions.
The most commonly referred to scale by the press and the public is the Richter scale for measuring earthquake magnitude. However this was actually replaced in the 1970s by the Moment Magnitude scale which is the magnitude scale favoured and in use by seismologists.
Seismometers measure the amplitude of seismic waves as well as the velocity and acceleration of the grounds surface. This allows seismologists to estimate the magnitude of an earthquake (the amount of energy released). From the energy emission per unit time they can estimate the power of the earthquake.
Magnitude of the 2011 Japan earthquake on moment magnitude scale is 9.0.The use of the Richter magnitude scale has largely been replaced by the moment magnitude scale in most countries. The United States Geological Survey (USGS), for example, uses the moment magnitude scale designated as MMS or Mw to measure all large earthquakes.UPDATE: Official magnitude was updated to 9.1 on Nov 7, 2016.
They could use the information from the seismic wave scale
The expression Richter Magnitude Scale refers to a number of ways to assign a single number to quantify the energy contained in an earthquake.In all cases, the magnitude is a base-10 logarithmic scale obtained by calculating the logarithm of the amplitude of waves measured by a seismograph. An earthquake that measures 5.0 on the Richter scale has a shaking amplitude 10 times larger and corresponds to an energy release of √1000 ≈ 31.6 times greater than one that measures 4.0.[1]Since the 1970s the use of the Richter Magnitude Scale has largely been supplanted by the moment magnitude scale
They use the Richter scale to measure magnitude and Moment Measure to measure energy released.
A Richter scale measures the power of a earthquake
Earthquake
Yes we still use the richtor scale today,, to find the force of the earthquake.
They measure the amplitude of the L waves to rate the earthquake.
You use a seismometer. Then, measure the magnitude according to the Richter scale.
The most commonly referred to scale by the press and the public is the Richter scale for measuring earthquake magnitude. However this was actually replaced in the 1970s by the Moment Magnitude scale which is the magnitude scale favoured and in use by seismologists.
No. The Richter scale (since replaced by the Moment Magnitude scale) was used to measure earthquake intensity. The Fujita scale (now the Enhanced Fujita scale in the U.S.) is used to rate tornadoes.
The Richter Scale to rate magnitude and seismograph to measure strength
Ritcher Scale
The most commonly used measurement for earthquakes today is the moment magnitude scale (Mw). It measures the total energy released by an earthquake by analyzing the seismic waves it generates. This scale provides a more accurate assessment of earthquake magnitude compared to older scales like the Richter scale.
Scientists use a machine called a seismometer to measure the strength of an earthquake. The calculated magnitude had been expressed on the Richter scale, a base 10 logarithmic scale, but with a usable limit of 6.5. Currently, magnitude is expressed on the Moment Magnitude Scale.