Distribution of earthquakes

Earthquakes do not happen at random. While some parts of the world witness more than one quake a day, others, more fortunate, may have almost never had one.
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Updated on May 22, 2003 11:49 AM IST
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PTI | By HT Correspondent

Earthquakes do not happen at random. While some parts of the world witness more than one quake a day, others, more fortunate, may have almost never had one. Why are earthquakes concentrated in some areas?

Earthquake risk is maximum along fault lines, at the contact zones between two plates, especially converging ones. As these fault lines lie largely at the margins of the tectonic or lithospheric plates, the surface areas corresponding to these are most frequented by earthquakes.

The Pacific rim witnesses earthquakes on a regular basis. About 80 per cent of the minor earthquakes that occur daily are in this region. Among the heavily populated areas that are affected in this region include Japan, South East Asian islands including Taiwan, Philippines and most of Indonesia, New Zealand and western coasts of North and South America.

Another zone of high seismic activity is at the meeting point the Eurasian plate with a number of smaller plates from the south, including the Indian. This Eurasian zone begins from under the Mediterranean Sea and travels through western Asia, the Himalayas, the Arakans, Sumatra and Java, meeting the circum Pacific belt.

Flinn-Engdahl Regions
A widely accepted scheme for earthquake distribution is the Flinn-Engdahl scheme, by which the world is broken down into regions based on geographic and political boundaries. The scheme, proposed in 1965 and revised in 1995, assigns a unique number to each region. The boundaries of these regions are defined at one-degree intervals and therefore differ from irregular political boundaries.

Seismic Region   1
Alaska - Aleutian Arc              
 
Seismic Region   2
Southeastern Alaska to Washington  
 
Seismic Region   3
Oregon, California and Nevada      
 
Seismic Region   4
Gulf of California                 
 
Seismic Region   5
Mexico - Guatemala Area            
 
Seismic Region   6
Central America                    
 
Seismic Region   7
Caribbean Loop                     
 
Seismic Region   8
Andean South America               
 
Seismic Region   9
Southern Chile and Argentina       
 
Seismic Region  10
Southern Antilles                  
 
Seismic Region  11
New Zealand Region                 
 
Seismic Region  12
Kermadec - Tonga - Samoa Area      
 
Seismic Region  13
Fiji Area                          
 
Seismic Region  14
Santa Cruz - Vanuatu Area          
 
Seismic Region  15
Bismarck and Solomon Islands       
 
Seismic Region  16
New Guinea                         
 
Seismic Region  17
Caroline Islands Area              
 
Seismic Region  18
Mariana, Volcano & Bonin Islands   
 
Seismic Region  19
Eastern Japan to Kamchatka         
 
Seismic Region  20
Western Japan and Ryukyu Islands   
 
Seismic Region  21
Taiwan Area                        
 
Seismic Region  22
Philippine Islands                 
 
Seismic Region  23
Kalimantan, Sulawesi & Moluccas    
 
Seismic Region  24
Sunda Arc  
                       
Seismic Region  25
Myanmar and Southeast Asia         
 
Seismic Region  26
India and Southwestern China       
 
Seismic Region  27
Southern Xinjiang to Gansu         
 
Seismic Region  28
Alma-Ata to Lake Baykal           
 
Seismic Region  29
Western Asia                      
 
Seismic Region  30
Middle East, Crimea and Balkans    
 
Seismic Region  31
Western Mediterranean Area         
 
Seismic Region  32
Atlantic Ocean                     
 
Seismic Region  33
Indian Ocean                       
 
Seismic Region  34
Eastern North America              
 
Seismic Region  35
Eastern South America              
 
Seismic Region  36
Northwestern Europe                
 
Seismic Region  37
Africa                             
 
Seismic Region  38
Australia                          
 
Seismic Region  39
Pacific Basin                   
  
Seismic Region  40
Arctic Zone                       

Seismic Region  41
Eastern Asia                       
 
Seismic Region  42
Eastern Siberia & Arctic America   
 
Seismic Region  43
Southeastern & Antarctic Pacific  
 
Seismic Region  44
Galapagos Islands Area             
 
Seismic Region  45
Macquarie Loop                     
 
Seismic Region  46
Andaman Islands to Sumatera        
 
Seismic Region  47
Afghanistan and Pakistan           
 
Seismic Region  48
Hindu Kush and Pamir Area          
 
Seismic Region  49
Northern Eurasia                   
 
Seismic Region  50
Antarctica

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