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Earthquake presages – A comprehensive approach

25.09.2006
Investigating earthquake presages not taken separately but comprehensively is enabled by the Russian-Japanese geophysical observatory, its establishment in Kamchatka being sponsored by the International Science and Technology Center.

By its capabilities, the observatory has no equal either in Russia or abroad. Being actually “stuffed” with state of the art equipment including custom designed facilities, the observatory gives the researchers a unique opportunity to simultaneously carry out seismic, electromagnetic, acoustic, hydrogeochemical and ionospheric observations.

The researchers have been looking for a location for the observatory for quite a long time. In Japan, for example, there is no place to establish it – the level of man-caused noises – both electromagnetic and acoustic – is too high. A quiet place was found in the forest, 60 kilometers from Petropavlovsk-Kamchatsky, in the valley of the small Karimshina River, far from large settlements and transmission facilities. Here, natural and industrial interference turned out to be minimal.

Although the scientists are rather cautious in evaluation of the work outcome, it is clear already that the researchers have managed to reveal a number of pretty interesting regularities. For example, they have noticed that by measuring the variable magnetic field gradient it is possible to learn about the earthquake when it is only imminent!

The field oscillation measurements in the 0.003-3 Hz range allow to discover coseismal (1 minute around time of seismic wave arrival), near seismic (3 hours before the earthquake) and pre-seismic (several days prior to the earthquake) electromagnetism. And the most important thing: the researchers have ascertained that several (2-6) days prior to a powerful and isolated earthquake, the elecromagnetic field intensity decreases in this range.

This finding was obtained having analyzed the data of the 13-month regular observations in Karimshin, during which 20 rather intense and close earthquakes took place. So, the researchers have chosen a good place for the observatory – there are sufficient shakes to apply both statistical analysis and individual case analysis. In the long run, hopefully, the researchers will find out how to learn about impending earthquake in advance. The forewarned is forearmed. Indeed, knowledge is power.

“The observatory consists of five individual measuring systems for observation, - says Alexander Lutikov, one of the project participants, chief research officer of the Geophysical Service and Institute of Physics of the Earth (Russian Academy of Sciences). - First of all, there is equipment for seismic, variable geomagnetic field and acoustic emission recording. In fact, in order to “listen” to the sounds of the Earth, particularly when microfissures are being formed, and not to be deceived, for example, by man-caused noises or sound of the wind, a special well (30 meters deep) was drilled for acoustic sensors. In the same location, temperature and soil waters composition is constantly measured at different depths in other wells. However, analysis of obtained samples is still carried out not at the observatory but at a special laboratory in Petropavlovsk-Kamchatsky. Although, in the future this should probably be performed “on the spot”, ideally – in the on-line mode.

Secondly, there is a measuring system for the so-called telluric currents, roughly speaking, electric currents in the earth’s crust surface layer. And, finally, there are systems for measuring meteorological factors and characteristics of radio signals from navigation transmitters.

The point is that the major part of measurements has so far been carried out and continues to be carried out at thousands of stations all over the world. However, this is the scattered data. Now, (and this is exceptionally important) all this data is for the first time comprehesively and simultaneously at the researchers’ disposal. That allows to investigate much fuller the processes preceding earthquakes and certainly the ones taking place during the earthquakes.”

To extend opportunities for investigations, two more stations were built to supplement the observatory, the stations being located at the distance of 5 and 60 kilometers from the observatory. They were mainly required to measure magnetic field pulsation. Identical inductive magnetometers were placed at each of these stations and at the observatory. These uniquely precise and sensitive devices designed by the Russian specialists participating in the project have no analogues in terms of characteristics. Observations carried out at three stations at once allow not only to measure geomagnetic fields much more precisely, but also to separate the changes caused by seismic activity from the background ones.

Since it is impossible to process manually such enormous data array, the researchers have developed special software for combined analysis of seismic, electromagnetic and acoustic signals as well as hydrochemical and meteorological parameters. They have also developed software for statistical analysis of signals and for distribution functions computation. The researchers even used special filtration programs to detect very weak signals.

Specialists of several entities were involved in the establishment of the observatory and now they conduct investigations actively. On the Russian part, these are the Geophysical Service of the Russian Academy of Sciences and the Institute of Physics of the Earth (Russian Academy of Sciences). The Japanese participants to the project include specialists of the Institute of Physical and Chemical Research (RIKEN), University of Electrocommunications and the Tokay (not to be confused with the Tokyo) University.

Nadezda Markina | alfa
Further information:
http://www.informnauka.ru

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