In the ocean off the coast of the eastern Russian Peninsia Kamchatka, a very powerful earthquake took place on Wednesday night at half past one with a magnitude of 8.8. Immediately the authorities issued a tsunami warning. The epicenter of the quake was 130 kilometers off the coast, in an area where seismic activity is the order of the day. But this quake was exceptionally powerful, and comes in sixth of the most powerful earthquakes ever measured.
“This is a remarkably powerful earthquake yes,” says earth scientist Rob Govers from Utrecht University. “Forces of 8.5 or larger are not more common worldwide than once or twice a decade. In the period from 1964 to 2004, there was not even a single earthquake that came close to a magnitude of 9.”
Messages about the damage to this quake seems to be not too bad come across as unbelievable on Govers. “The epicenter of the main shock was no more than 130 to 150 kilometers from the nearest city, Petropavlovsk, with 200,000 inhabitants. It is only possible that buildings have also been damaged and victims have been damaged there. In addition, the epicenter is actually not one point. It is a swarm of larger and smaller earth shock that extends to an area of a lot of area of the area that extends to one area of 400. minimal. ”
The area where the earthquake took place is a well-known subduction zone, an area where the Pacific earth plate slides under the North American plate. There is a deep trough on the seabed where sliding stresses between the overlapping earth plates occur, and behind it a ring of volcanoes where magma rises. “Geologists expect large earthquakes here, certainly because the tectonic movement here is pretty fast, with a shift of up to eight centimeters a year. The tension between the plates is rapidly rising until it comes loose with an earthquake as a result. There are constantly smaller quakes, with sometimes a powerful outlier, there was also an earthen breeze in 1952 also in the last of 1952 in Kamtsjatka with Kamtsjatka. area already a quake that we now see as front shock, with a force of 7.5. ”
Subduction areas are notorious because an earthquake there can potentially lead to a large tsunami. Sudden movements of the deep seabed transfer a lot of energy to the water column above it, causing a wave to be generated. The tsunami is virtually unrestrained in the deep water of the ocean, which explains that now to Chile and New Guinea tsunamiwaars have been issued.
In deep water, the Golf goes at a thousand kilometers per hour, “just as fast as a trafficplace,” says Govers. But arriving at a coast across the street, the water becomes shallower and a stowage is created, “just like cars that come in a traffic jam.” Where the tsunami on the open ocean was still a wave of a few dozen centimeters, he can swell on the coast to a meter -high wave. “The only side that the water can go there is up,” says Govers. Often the sea first retreats on the coast, and then returns to a large tidal wave or series of waves.
The enormous water mass can cause major destruction, also across the ocean. “We also saw that in 2004 at the great quake at Sumatra, where a tsunami also caused a lot of victims in the African country of Somalia, across the Indian Ocean.”
Incidentally, Govers notes that the provision of information from the US government is much scorer than normal-the effect of cuts by the US government Trump, he thinks. “Normally we get a detailed analysis about two hours after such a powerful earthquake about how it went exactly. Very important for estimating the severity of a possible tsunami, for example, whether the break after the initial shock at great depth has moved to poet below the surface. That information is difficult to estimate how it will now work further.”
The relocation of the tsunami is now still mapped by a limited number of measuring stations in the ocean that measure the pressure change on the seabed and so see the tsunamigolf of approximately fifty centimeters passing by. Govers also expects large disasters to be prevented because people along the ocean coast can still be warned to flee to higher areas on time.