The Earth's seismic belts are lines along which the boundaries between lithospheric plates pass. If the plates move towards each other, then mountains form at the junctions (such areas are also called mountain-building zones). If the lithospheric plates diverge, then faults appear in these places. Naturally, processes such as the convergence and divergence of lithospheric plates do not remain without consequences - about 95% of all earthquakes and volcanic eruptions occur in these areas. That is why they are called seismic (from the Greek seismos - to shake).
It is customary to distinguish two main seismic belts: the latitudinal Mediterranean-Trans-Asian and the meridional Pacific, perpendicular to it. The vast majority of all earthquakes occur in these two areas. If you look at the seismic hazard map, it becomes clearly visible that the zones highlighted in red and burgundy are located precisely at the location of these two belts. They extend for thousands of kilometers, circling the globe, on land and under water.
Almost 80% of all earthquakes and volcanic eruptions occur in the Pacific Seismic Belt, otherwise known as the Pacific Ring of Fire. This seismic zone really, as if in a ring, envelops almost the entire Pacific Ocean. There are two branches of this belt - Eastern and Western.
The eastern branch starts from the shores of Kamchatka and goes through the Aleutian Islands, passes through the entire western coast of North and South America and ends in the South Antilles loop. In this area, the most powerful earthquakes occur on the California Peninsula, which determines the architecture of cities such as Los Angeles and San Francisco - they are dominated by houses one or two stories high with the occasional multi-story building, mainly in the central parts of the cities.
The western branch of the Pacific Ring of Fire stretches from Kamchatka through the Kuril Islands, Japan and the Philippines, covers Indonesia and, arcing around Australia, through New Zealand reaches Antarctica itself. This area experiences many powerful underwater earthquakes, often leading to catastrophic tsunamis. Island countries such as Japan, Indonesia, Sri Lanka, etc. suffer the most from earthquakes and tsunamis in this region.
The Mediterranean-Trans-Asian Belt, as its name suggests, extends across the entire Mediterranean Sea, including the southern European, northern African and Middle Eastern regions. Then it stretches across almost all of Asia, along the ridges of the Caucasus and Iran to the Himalayas, to Myanmar and Thailand, where, according to some scientists, it connects with the seismic Pacific zone.
According to seismologists, this belt accounts for about 15% of the world's earthquakes, while the most active zones of the Mediterranean-Trans-Asian belt are considered to be the Romanian Carpathians, Iran and eastern Pakistan.
Secondary seismic belts
There are also secondary zones of seismic activity. They are considered secondary because they account for only 5% of all earthquakes on our planet. The seismic belt of the Atlantic Ocean begins off the coast of Greenland, stretches along the entire Atlantic and finds its end near the islands of Tristan da Cunha. There are no strong earthquakes here, and due to the remoteness of this zone from the continents, tremors in this belt do not cause destruction.
The Western Indian Ocean is also characterized by its own seismic zone, and although it is quite large in length (its southern end reaches as far as Antarctica), earthquakes here are not too strong, and their foci are located shallow underground. There is also a seismic zone in the Arctic, but due to the almost complete desolation of these places, as well as due to the low power of tremors, earthquakes in this region do not have a particular impact on people’s lives.
The most powerful earthquakes of the 20th-21st centuries
Since the Pacific Ring of Fire accounts for up to 80% of all earthquakes, the main cataclysms in terms of their power and destructiveness occurred in this region. First of all, it is worth mentioning Japan, which has repeatedly become a victim of severe earthquakes. The most destructive, although not the strongest in terms of the magnitude of its fluctuations, was the earthquake of 1923, which is called the Great Kanto Earthquake. According to various estimates, 174 thousand people died during and from the consequences of this disaster, another 545 thousand were never found, the total number of victims is estimated at 4 million people. The most powerful Japanese earthquake (with a magnitude of 9.0 to 9.1) was the famous disaster of 2011, when a powerful tsunami caused by underwater tremors off the coast of Japan caused destruction in coastal cities, and a fire at a petrochemical complex in the city of Sendai and an accident at The Fokushima-1 nuclear power plant caused enormous damage to both the economy of the country itself and the environment of the whole world.
The most powerful Of all the documented earthquakes, the Great Chilean earthquake with a magnitude of up to 9.5, which occurred in 1960, is considered (if you look at the map, it becomes clear that it also occurred in the region of the Pacific seismic belt). The disaster that claimed the largest number of lives in the 21st century was the 2004 Indian Ocean earthquake, when a powerful tsunami, which was its consequence, claimed almost 300 thousand lives from almost 20 countries. On the map, the earthquake zone refers to the western tip of the Pacific Rim.
Many large and destructive earthquakes also occurred in the Mediterranean-Trans-Asian seismic belt. One of these is the 1976 Tangshan earthquake, when according to official Chinese data alone, 242,419 people died, but according to some sources, the number of victims exceeds 655 thousand, which makes this earthquake one of the deadliest in human history.
