When the Earth trembles, earthquakes spread energy in the form of seismic waves. A seismograph is the primary earthquake measuring instrument. The seismograph produces a digital graphic recording of the ground motion caused by the seismic waves. The digital recording is called a seismogram. The seismograph produces a digital graphic plotting of the ground motion of the event.
An earthquake has one magnitude unit. The magnitude does not depend on the location where measurement is made. Since , the Moment Magnitude Scale has been used because it supports earthquake detection all over the Earth.
To get a better idea of the strength of the shaking and damage, the Moment Magnitude Scale was developed to capture all the different seismic waves from an earthquake to worldwide seismic networks. There can be multiple intensity measurements.
The Modified Mercalli Scale measures the amount of shaking at a particular location. An important piece of information to keep in mind is that the magnitude scale is logarithmic.
This helps us understand that while the size amplitude differences between small and big quakes are big enough, it is the strength energy differences that are meaningful. From until , the earthquake magnitude scale was the Richter scale, a mathematical formula invented by Caltech seismologist Charles Richter to compare quake sizes.
The Richter Scale was replaced because it worked largely for earthquakes in Southern California, and only those occurring within about miles of seismometers.
In addition, the scale was calculated for only one type of earthquake wave. It was replaced with the Moment Magnitude Scale, which records all the different seismic waves from an earthquake to seismographs across the world. Richter's equations are still used for forecasting future earthquakes and calculating earthquake hazards.
MMS measures the movement of rock along the fault. It accurately measures larger earthquakes, which can last for minutes, affect a much larger area, and cause more damage. Earthquakes are also classified in categories ranging from minor to great, depending on their magnitude.
It is logarithmic which means, for example, that an earthquake measuring magnitude 5 is ten times more powerful than an earthquake measuring 4. Earthquakes measuring on the scale happen regularly, and they are so small that people cannot feel them.
Liquefaction can also cause severe mudslides. Sign up for our Newsletter! Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. Mobile Newsletter chat avatar. Mobile Newsletter chat subscribe. Prev NEXT. Forces of Nature. Natural Disasters. How can an earthquake affect groundwater or changes in wells?
Groundwater levels in wells may oscillate up and down while seismic waves pass, and in some cases, the water level may remain higher or lower for a period of time after the seismic wavetrain has ended. What are those booms I sometimes hear before or during an earthquake? Of course, most "booms" that people hear or experience are actually some type of cultural noise, such as some type of explosion, a large vehicle going by, or sometimes a sonic boom, but there have been many reports of "booms" At what magnitude does damage begin to occur in an earthquake?
It isn't that simple. There is not one magnitude above which damage will occur. It depends on other variables, such as the distance from the earthquake, what type of soil you are on, etc. That being said, damage does not usually occur until the earthquake magnitude reaches somewhere above 4 or 5. Learn more: Earthquake Magnitude, Energy Release, Filter Total Items: 5. Year Published: Shaking intensity from injection-induced versus tectonic earthquakes in the central-eastern United States Although instrumental recordings of earthquakes in the central and eastern United States CEUS remain sparse, the U.
Hough, Susan E. View Citation. Year Published: The ShakeOut Scenario This is the initial publication of the results of a cooperative project to examine the implications of a major earthquake in southern California. Jones, Lucile M. Year Published: Did you feel it?
Wald, David J. Did you feel it? Boatwright, J. Year Published: Earthquake Shaking - Finding the "Hot Spots" A new Southern California Earthquake Center study has quantified how local geologic conditions affect the shaking experienced in an earthquake.
Field, Edward H. Filter Total Items: 6. Date published: April 24, Date published: March 28, Date published: March 1, Attribution: Science Application for Risk Reduction. Date published: October 17, Attribution: Natural Hazards. Date published: May 18,
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