There are special zones of increased seismic activity on Earth, where earthquakes constantly occur. Why is this happening? Why do earthquakes occur more often in mountainous areas and very rarely in deserts? Why do earthquakes occur constantly in the Pacific Ocean, generating tsunamis of varying degrees of danger, but we have heard almost nothing about earthquakes in the Arctic Ocean. It's all about the seismic belts of the earth.
Introduction
The earth's seismic belts are places where the planet's lithospheric plates come into contact with each other. In these zones, where the Earth's seismic belts are formed, there is increased mobility of the earth's crust and volcanic activity caused by the process of mountain building, which lasts for millennia.
The length of these belts is incredibly large - the belts stretch for thousands of kilometers.
There are two large seismic belts on the planet: the Mediterranean-Trans-Asian and the Pacific.
Rice. 1. Seismic belts of the Earth.
Mediterranean-Trans-Asian The belt originates off the coast of the Persian Gulf and ends in the middle of the Atlantic Ocean. This belt is also called the latitudinal belt, since it runs parallel to the equator.
Pacific belt– meridional, it stretches perpendicular to the Mediterranean-Trans-Asian belt. It is along the line of this belt that a huge number of active volcanoes are located, most of whose eruptions occur under the water column of the Pacific Ocean itself.
If you draw the Earth's seismic belts on a contour map, you will get an interesting and mysterious picture. The belts seem to border the ancient platforms of the Earth, and sometimes penetrate into them. They are associated with giant faults in the earth's crust, both ancient and younger.
Mediterranean-Trans-Asian seismic belt
The Earth's latitudinal seismic belt passes through the Mediterranean Sea and all the adjacent European mountain ranges located in the south of the continent. It stretches through the mountains of Asia Minor and North Africa, reaches the mountain ranges of the Caucasus and Iran, and runs through all of Central Asia and the Hindu Kush straight to Koel Lun and the Himalayas.
In this belt, the most active seismic zones are the Carpathian Mountains, located in Romania, all of Iran and Baluchistan. From Baluchistan the earthquake zone stretches to Burma.
Fig.2. Mediterranean-Trans-Asian seismic belt
This belt has active seismic zones, which are located not only on land, but also in the waters of two oceans: the Atlantic and Indian. This belt also partially covers the Arctic Ocean. The seismic zone of the entire Atlantic passes through the Greenland Sea and Spain.
The most active seismic zone of the latitudinal belt occurs at the bottom of the Indian Ocean, passes through the Arabian Peninsula and stretches to the very south and southwest of Antarctica.
Pacific belt
But, no matter how dangerous the latitudinal seismic belt is, the majority of all earthquakes (about 80%) that occur on our planet occur in the Pacific belt of seismic activity. This belt runs along the bottom of the Pacific Ocean, along all the mountain ranges encircling this largest ocean on Earth, and captures the islands located in it, including Indonesia.
Fig.3. Pacific seismic belt.
The largest part of this belt is the Eastern one. It originates in Kamchatka, stretches through the Aleutian Islands and the western coastal zones of North and South America straight to the South Antilles loop.
The eastern branch is unpredictable and little studied. It is full of sharp and twisting turns.
The northern part of the belt is the most seismically active, which is constantly felt by residents of California, as well as Central and South America.
The western part of the meridional belt originates in Kamchatka, stretches to Japan and beyond.
Secondary seismic belts
It is no secret that during earthquakes, waves from vibrations of the earth's crust can reach remote areas that are generally considered safe with regard to seismic activity. In some places, the echoes of earthquakes are not felt at all, and in others they reach several points on the Richter scale.
Fig.4. Map of Earth's seismic activity.
Basically, these zones, sensitive to vibrations of the earth's crust, are located under the water column of the World Ocean. The planet's secondary seismic belts are located in the waters of the Atlantic, Pacific Ocean, Indian Ocean and the Arctic. Most of the secondary belts are located in the eastern part of the planet, so these belts stretch from the Philippines, gradually descending to Antarctica. The echoes of tremors can still be felt in the Pacific Ocean, but in the Atlantic there is almost always a seismically calm zone.
What have we learned?
So, on Earth, earthquakes do not occur in random places. It is possible to predict the seismic activity of the earth's crust, since the bulk of earthquakes occur in special zones called seismic belts of the earth. There are only two of them on our planet: the Latitudinal Mediterranean-Trans-Asian seismic belt, which stretches parallel to the Equator, and the meridional Pacific seismic belt, located perpendicular to the latitudinal one.
