The analysis proved that between 1982 and 1993, earthquake frequency reduced drastically, the foci of earthquakes being located at the depth of less than 70 kilometers (known as shallow-focus earthquakes). Less powerful earthquakes (magnitude 7-7.5) took place 3-4 times less often during that period, and more powerful earthquakes (magnitude 8 and higher) – 10 times less often as compared to the previous and subsequent periods.
The most powerful shallow-focus earthquakes (magnitude exceeding 8.5 scores) arouse special interest. Between 1965 and 2001 there were none at all, and after 2001 occurred almost every year. These include the strongest shocks near the Sumatran coast on December 26, 2004 and on March 28, 2005, which were followed by gigantic tsunami.
After the eleven-year calm, deep-focus earthquakes also occurred. Up to mid-1993, there were no deep-focus earthquakes over 7 in magnitude, but between the end of 1993 and 2005, researchers recorded 12 earthquakes with magnitudes of 7.5, four with magnitudes of 8, and one with magnitude of 8.8. This most violent earthquake took place in the Atlantic Ocean near the eastern coast of South America at the depth of about 90 kilometers. As per relatively weak deep-focus events with magnitudes of about seven, they happened about five times a year since mid-1993 and later (which is several times more often than during the calm period).
Deep-focus earthquakes are connected with submersion of lithospheric plates into the upper earth mantle. It is probable that plates used to submerge slowly and smoothly during the calm period, thus loosening the tension in the earth lithosphere and reducing the number of seismic events in it. It is also possible that slow submersion of lithospheric plates contributes to the accumulation of geodynamic tension, followed by relaxation – elastic stress falloff in the form of earthquakes.
To confirm these findings, V.I. Ulomov listed several recent events that signify violent seismic activity of last decades:
- April 21, 2006 – an earthquake took place in Kamchatka (magnitude 7.6-7.8);
- November 15, 2006 – the most violent earthquake in the world in terms of magnitude took place in the central part of the Kurile Islands (magnitude 8.3 and 10-11-score seismic effect in the epicentre).
- January 13, 2007 – one more earthquake happened (magnitude 8.2) in the same focal area of the Kurile Islands, where the largest in magnitude earthquake had occurred two month before that.
- Quite recently, on September 12, 2007 – a recurrent violent earthquake (magnitude 8.4) occurred near Sumatra coast.
Nadezda Markina | alfa
Satellites reveal bird habitat loss in California
28.03.2017 | Duke University
Northern oceans pumped CO2 into the atmosphere
27.03.2017 | CAGE - Center for Arctic Gas Hydrate, Climate and Environment
The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.
To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
28.03.2017 | Physics and Astronomy
28.03.2017 | Health and Medicine
28.03.2017 | Life Sciences