|Richter Magnitude Scale in Seismology (Study of earthquakes)|
- Mr. Subrahmanyam D.
|Seismologists use a Magnitude scale to express the seismic energy
released by each earthquake. Here are the typical effects of
earthquakes in various magnitude ranges:
Earthquake Severity Richter Earthquake Magnitudes Effects
Less than 3.5 Generally not felt, but recorded.
3.5-5.4 Often felt, but rarely causes damage.
Under 6.0 At most slight damage to well-designed buildings.
Can cause major damage to poorly constructed buildings
over small regions.
6.1-6.9 Can be destructive in areas up to about 100 kilometers
across where people live.
7.0-7.9 Major earthquake. Can cause serious damage over
8 or greater Great earthquake. Can cause serious damage in areas
several hundred kilometers across.
Though this is a very generalised scale it provides a very good
estimate from the damage information obtained
What about the energy released during earth quakes with respesct to
the Richter magnitude? Here is the table with examples
Here we assume one ounce of TNT exploded below ground yields 640
million ergs of seismic wave energy
Richter TNT for Seismic Example
Magnitude Energy Yield (approximate)
-1.5 6 ounces Breaking a rock on a lab table
1.0 30 pounds Large Blast at a Construction Site
1.5 320 pounds
2.0 1 ton Large Quarry or Mine Blast
2.5 4.6 tons
3.0 29 tons
3.5 73 tons
4.0 1,000 tons Small Nuclear Weapon
4.5 5,100 tons Average Tornado (total energy)
5.0 32,000 tons
5.5 80,000 tons Little Skull Mtn., NV Quake, 1992
6.0 1 million tons Double Spring Flat, NV Quake, 1994
6.5 5 million tons Northridge, CA Quake, 1994
7.0 32 million tons Hyogo-Ken Nanbu, Japan Quake, 1995;
Largest Thermonuclear Weapon
7.5 160 million tons Landers, CA Quake, 1992
8.0 1 billion tons San Francisco, CA Quake, 1906
8.5 5 billion tons Anchorage, AK Quake, 1964
9.0 32 billion tons Chilean Quake, 1960
10.0 1 trillion tons (San-Andreas type fault circling Earth)
12.0 160 trillion tons (Fault Earth in half through center,
OR Earth's daily receipt of solar energy)
That is really terrible. Is it Not? The last Tsunami is of 9.5
magnitude on Richter scale That means it has released an energy
equivelent to the energy produced by blasting 32 billion tons to 1 trillion tons on TNT.
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