Measuring the Damage

©1995 The Regents of the University of California

Using the Richter and Mercali Scales

Richter Scale The Richter Scale measures the energy of an earthquake by determining the size of the greatest vibrations recorded on a seismogram. On this scale, one step up in magnitude (from 5.0 to 6.0, for example) increases the energy more than 30 times.

Richter Magnitude How many kilograms of TNT would have this much energy?


0	                 0.6	


1.0	               20	  


2.0	               600	                *  Smallest quake people can normally feel


3.0	               20 000   	        *  Most people near epicenter feel the quake
       
                                              *  Nearly 100, 000 occur every year of size 2.5 - 3.0

4.0	               60 000	           *  A small fission atomic bomb

                                              *  Quakes above 4.5 can cause local damage
  
5.0	               20 000 000	    *  A standard fission bomb, similar to the first bomb tested in New 
                                   Mexico, U.S.

6.0	               60 000 000  	  *  A hydrogen bomb;  can cause great damage locally

                                             *  About 100 shallow quakes of size 6.0 every year

7.0	               20 billion	      *  Major earthquake;  about 14 every year

                                             *  Enough energy to heat New York City for 1 year

                                             *  Large enough to be detected all over globe

8.0	               60 billion	      *  Largest known:  8.9 in Japan and in Chile/Ecuador

                                             *  San Francisco destroyed by 8.25 in 1906

9.0	               20 trillion	    *  Roughly the world’s energy usage in a year

Mercali Scale<.p The Mercali Scale measures an earthquake according to the observable results or effects the damage caused, the sensations described by people, etc. (Mercali numbers do not correspond directly to Richter numbers; for example, V on the Mercali Scale is not equivalent to 5 on the Richter Scale).

Mercali Magnitude Observable Results and Effects

I	    Most people do not notice,  animals may be uneasy,  can be detected by a 
      seismograph

II Hanging objects sway back and forth
III Many people feel the movement, parked cars may rock
IV Doors, windows, and shelves may rattle, people indoors can feel movement
V Light furniture moves, pictures fall off walls, objects fall from shelves
VI Nearly everyone feels movement, light furniture falls over, windows may crack
VII Some people fall over, walls may crack
VIII Heavy furniture falls over, some walls crumble
IX Many people panic, some buildings collapse, dams crack
X Railroad lines are bent, most buildings are damaged, roads crack
XI Bridges collapse, buried pipes break, most buildings collapse
XII All manmade structures are destroyed


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