The earthquake of magnitude 8.8 that shook the coast of the Kamchatka Peninsula, at the eastern end of Russia, is one of the ten strongest in history and the largest in the world since 2011. This earthquake has caused damage to buildings and wounded in the largest nearby city, Petropávlovsk-Kamchatski, only 119 kilometers from the epicenter.
Tsunami alerts and evacuations have resonated in Russia, Japan and Hawaii, and notices have been issued for the Philippines, Indonesia and places as far away as New Zealand and Peru.
The Pacific region is very prone to great intensity earthquakes and the tsunamis that they cause, since it is in the so -called fire belt, an area of high seismic and volcanic activity. The ten most powerful earthquakes recorded in modern history occurred in that region.
Here is why the underlying structure of our planet makes this part of the world so unstable.
Why are such strong earthquakes in Kamchatka?
Just in front of the Kamchatka Peninsula coast is Kuril-Kamchatka’s pit, a tectonic plaque limit where the Pacific plate pushes under the Okhotsk plate.
While tectonic plates move continuously with respect to others, interconnection between them is usually “stuck.” The voltage accumulates until the resistance of said contact zone exceeds, at which time is released in the form of sudden rupture: an earthquake occurs.
Due to the large extensions of the contact points in the limits of the plates, both in length and in depth, the break can cover large areas. This results in some of the largest and most potentially destructive earthquakes on Earth.
Another factor that influences the frequency and magnitude of earthquakes in subduction areas is the speed at which the two plates move together.
In the case of Kamchatka, the Pacific plaque moves to approximately 75 millimeters per year with respect to Okhotsk. It is a relatively high speed for tectonic standards, which causes large earthquakes to be more frequent here than in other subduction areas. In 1952, there was an earthquake of magnitude 9.0 in the same subduction zone, just about 30 kilometers from the magnitude earthquake 8.8 produced today.
Other examples of earthquakes in subduction plates limits are the earthquake of 9.1 magnitude of Tohoku-Oki (Japan) of 2011 and the earthquake of magnitude 9.3 of Sumatra-Andaman Indonesia, occurred in 2004. Both began at a relatively low depth and broke the limit of the plate to the surface.
They raised one side of the seabed with respect to the other, displacing the ocean that was on it and causing devastating tsunamis. In the case of the earthquake of December 26, 2004, the rupture of the seabed occurred over about 1400 km.
What is likely to happen next?
At the time of writing this article, approximately six hours after the earthquake, 35 replicas of magnitude greater than 5.0 have already occurred, according to the United States geological service.
Replicas occur when tension within the earth’s crust is redistributed after the main earthquake. They are often of a magnitude lower than that of the main earthquake. In the case of today’s earthquake, that means that they are possible replicas of magnitude greater than 7.5.
In an earthquake of this magnitude, replicas can continue for weeks or months, but normally decrease in magnitude and frequency over time.
Today’s earthquake has also caused a tsunami that has already affected the coastal communities of the Kamchatka Peninsula, the Kuriles and Hokkaido Islands in Japan.
In the next few hours, that tsunami will spread through the Pacific, arriving in Hawaii approximately six hours after the earthquake and continuing to Chile and Peru.
Scientists specialized in Tsunamis will continue to improve their models of their effects as it spreads, and civil defense authorities will provide official information on the local effects planned.
What lessons can be extracted from this earthquake for other parts of the world?
Fortunately, earthquakes as large as today’s are rare. However, its effects at the local level and worldwide can be devastating.
Apart from its magnitude, several aspects of today’s earthquake in Kamchatka will make it an especially important research focus.
For example, the area has been very active seismically in recent months, and on July 20 there was an earthquake of magnitude 7.4. The way in which this previous activity has affected the location and time of the event today will be a crucial aspect of the investigation.
Like Kamchatka and northern Japan, New Zealand is also on a subduction zone; In fact, on two subduction zones. The largest of them, the Hikurangi subduction zone, extends inside along the east coast of the North Island.
According to the characteristics of these points of contact between plaques and the geological records of past earthquakes, it is likely that the Hikurangi subduction zone will be able to produce earthquakes of magnitude 9. It has not done so in historical times, but if it happened, it would cause a tsunami.
The threat of a large earthquake in the subduction zone never disappears. Today’s earthquake in Kamchatka is an important reminder for all who live in areas prone to earthquakes that must be kept safe and pay attention to the warnings of the civil defense authorities.
Dee Ninis, Earthquake Scientist, Monash University and John Townend, Professor of Geophysics, ((Link: external ||| https: //theconversation.com/institts/te-herenga-waka-victoria- university-of-f-wellington-1200 ||| Waka herenga-Victoria University of Wellington))
This article was originally published in The Conversation. Read the original.
