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Recent Earthquakes

Nepal was hit by a 7.8 magnitude earthquake on April 25th, 2015.

Powerful 8.3 earthquake strikes Chile sending of tsunami warnings and evacuations of 1 million.

Afghanastan was hit by a 7.5 magnitude earthquake as reported by the U.S. Geological Survery, on October 26th, 2015.

Magnitude 6.9 earthquake strikes 106 km south east of Amahai, Indonesia.


 

  Earthquake Richter Scale

In an attempt to quantify and assign a magnitude of energy released from earthquakes to a scale the Richter Scale a base-10 logrithmic scale was developed defining the ratio of amplitude of seismic waves to an arbitrary, minor amplitude (Wikipedia, 2015). Each whole number increase of magnitude represents an increase of 10 time in amplitude corresponding to an increase of about 31.6 times the energy released. So, an increase of 0.2 in a doubling of energy released. A earthquake registering on the Richter Scale as a 6.0 by a seismometer has a shaking amplitude 10 times stronger than a 5.0 earthquake. This would indicate a difference of energy release of 31.6 times stronger by the 6.0 earthquake over the 5.0 earthquake.

This scale was developed in the 1930's but has been succeeded more recently in the 1970 by the Moment Magnitude Scale (MMS) by the U.S. Geological Survey. Earthquakes today are commonly incorrectly referred to as an earthquake registering on the Richter Scale when it should be reported as registering on the Moment Magnitude Scale (MMS).

The following describes the typical effects of earthquakes of various magnitudes near the epicenter. The values are typical only and should be taken with extreme caution, since intensity and thus ground effects depend not only on the magnitude, but also on the distance to the epicenter, the depth of the earthquake's focus beneath the epicenter, the location of the epicenter and geological conditions (certain terrains can amplify seismic signals).

The chart below shows values are only typical values of various magnitudes, description and damage near epicenters from earthquakes and should be taken with extreme caution because the intensity is dependent on variables such as magnitude, distance from epicenter, depth of the earthquakes focus and other various geological conditions such as lithology, terrain, porosity, etc.

Earthquake Richter Scale magnitude, description and damage.

Modified from Wikipedia, 2015 and based on U. S. Geological Survey documents.

References:

MSN News, 2015, Powerful Chile Quake Kills at least eight and 1 Million Evacuated

United States Geological Survey, 2014 Earthquake Magnitude Policy (implemented on January 18, 2002)

Wikipedia, 2015, Richter Magnitude Scale

William Spence, Stuart A. Sipkin, and George L. Choy, 1989, Earthquakes and Volcanoes
Volume 21, Number 1

 
 

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