Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Diary of earthquake observation

01.10.2007
The eleven years from 1982 to 1993 were surprisingly calm in the seismic chronicle of the Earth. A period of heavy and frequent earthquakes began in 1993 with a magnitude exceeding 7 points according to the 9-score Richter scale. The phenomenon was discovered by Valentin Ulomov, specialist of the Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, after analysing 600 large-scale earthquakes between 1965 and 2005.

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
Further information:
http://www.informnauka.ru

More articles from Earth Sciences:

nachricht AWI researchers measure a record concentration of microplastic in arctic sea ice
24.04.2018 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

nachricht Climate change in a warmer-than-modern world: New findings of Kiel Researchers
24.04.2018 | Christian-Albrechts-Universität zu Kiel

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: BAM@Hannover Messe: innovative 3D printing method for space flight

At the Hannover Messe 2018, the Bundesanstalt für Materialforschung und-prüfung (BAM) will show how, in the future, astronauts could produce their own tools or spare parts in zero gravity using 3D printing. This will reduce, weight and transport costs for space missions. Visitors can experience the innovative additive manufacturing process live at the fair.

Powder-based additive manufacturing in zero gravity is the name of the project in which a component is produced by applying metallic powder layers and then...

Im Focus: Molecules Brilliantly Illuminated

Physicists at the Laboratory for Attosecond Physics, which is jointly run by Ludwig-Maximilians-Universität and the Max Planck Institute of Quantum Optics, have developed a high-power laser system that generates ultrashort pulses of light covering a large share of the mid-infrared spectrum. The researchers envisage a wide range of applications for the technology – in the early diagnosis of cancer, for instance.

Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of...

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Getting electrons to move in a semiconductor

25.04.2018 | Physics and Astronomy

Reconstructing what makes us tick

25.04.2018 | Physics and Astronomy

Cheap 3-D printer can produce self-folding materials

25.04.2018 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>