Revival Of The Clay Jug Method

A long time ago, people inhabiting settlements at the boarder of Dykoye Pole (Wild Field) used to bury empty jugs into the ground: if they started buzzing this meant that a cavalry detachment was galloping across the steppe and it was time to escape to the outpost from the foray. Specialists of the Institute of Physics of the Earth, Russian Academy of Sciences, suggest a similar way for tracking oncoming natural disasters like earthquakes or catastrophic landslides.

“The main task of the forecast is to get a reliable warning about the time and place of a destructive event. The task can be simplified if the long-term observation location is chosen in advance – in that case the major effort can be focused on determination of time of disaster in that particular region. To this end, it is necessary to deploy the observation network within the bounds of a big town or in the vicinity of particularly important objects,” says Alexy Nikolayev, Corresponding Member of the Russian Academy of Sciences. One of the observation methods applied may be the measurement of noise which occurs in the the interior of the Earth.

The history of the method dates back to slightly more than a century. In any case, at the end of the 19th century, De Rossi from Rome installed a microphone at the depth of 20 meters and discovered a multitude of various sounds. Sometimes they became unbearably loud, especially once, half an hour prior to an earthquake. Back in the 50s of the last century, Professor Rikitake from the Tokyo Earthquake Research Institute came to the conclusion that investigation of vibrations in the audio-frequency range might be useful for disaster forecasting. In Russia, research of the “Earth’s voice” started twenty years ago. In 1999-2000, researchers placed sensors in Obninsk, Kislovodsk and Petropavlovsk-Kamchatski, the sensors being installed in deep boreholes (about one hundred meters deep), and since that time they have been accumulating statistics in order to later correlate parameters of sounds heard with certain events. Sometimes they manage to do that. Thus, the sensors in Kislovodsk proved that the noise produced by the interior of the Earth was evidently louder during massive bombing of Iraq in March 2003 than that after downfall of Bagdad and the campaign termination.

It has turned out that the sound in the earth’s crust is capable of passing enormous distances and informing about catastrophes that happened thousand of kilometers away. For example, at night of 16/17 February 1998, the “Moskva”seismic station (geophysical service of the Russian Academy of Sciences) recorded the sound of a powerful earthquake that had occurred in the North of the Atlantic Ocean. ‘It is amazing that sensors managed to hear such a signal in a megapolis where the noise is very intense anyway, says A.V. Nikolayev. We have only to regret that subterranean background noise research has not achieved adequate development for a long time”. The situation is being improved both by new devices for audio signal recording and visualization, and constant measurements of the sound which started in 2000. Concurrent accumulation of data in the areas of high seismicity (Kislovodsk) and of low seismicity (Obninsk) allow to discover synchronous variations of audio parameters and to determine their correlation with seismic activity.