Bulgarian Scientist: Pernik Quake Is Phenomenal Globally
The mechanism of the 5.8 magnitude on the Richter scale earthquake that shook western Bulgaria on May 22 is phenomenal on a global scale.
The explanation was made by the Head of the Seismology Department at the National Institute in Geophysics, Geodesy and Geography, at the Bulgarian Academy of Sciences, BAS, Emil Botev, saying that the tearing of the earth layers has been very slow and on a very steep slope.
The expert explained that during the quake the maximum energy of radiation has shifted to very low frequencies of vibration, generating an undulation in space which created the impression that the quake was happening far away and not just kilometers from the western city of Pernik. The lack of significant structure and building damage, compared to the 1986 5.7 on the Richter scale quake in the village of Strazhitsa in central Bulgaria, is also attributed to this mechanism.
Botev further clarifies that according to the magnitude scale, the Pernik shocks are considered a "moderate, not strong earthquake." Shocks from 0 to 3 are classified as micro quakes; from 3 to 4 – very weak; from 4 to 5 – weak, and from 5 to 6 – moderate.
Quakes from 6 to 7 are listed as strong; over 7 – catastrophic; over 8 – devastating, demolishing everything, not just what has been built by people, while those over 9 change in less than a second the period of rotation and the axis of the Earth and the entire landscape, says he.
The epicenter in Pernik is also unique because this is the very first time such strong tremors have been registered in the course of history, on the backdrop of several hundreds of prior weaker shocks that were never felt.
According to the expert, over 100 000 quakes with a magnitude of over 2 points are registered globally each year while 5-6 quakes with a magnitude of over 9 points happen in 100 years.
Some of the strongest earthquakes he mentioned are: 9.5 in 1960 in Chile, 9 in 1964 in Alaska, 9.3 in 2004 in Sumatra, 8.9 in 2010 again in Chile, and 9.1 in 2011 in Japan.
The strongest earthquakes happen through contacts between tectonic plates, which are mainly linked to the Pacific region, explained Botev. He added that these earthquakes produce "fantastic" tsunami waves that cause great devastation.
In Bulgaria, it is assumed that the strongest earthquake occurred in 1904 in the Kresna Gorge near the village of Krupnik. The magnitude was 7.8 on the Richter, the BAS expert reminded.
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