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 Climate satellite: Tracking methane with robust laser technology
22.06.2017 | Fraunhofer-Gesellschaft

nachricht How reliable are shells as climate archives?
21.06.2017 | Leibniz-Zentrum für Marine Tropenforschung (ZMT)

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>