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.

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?

HT Image

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