Noise ocean surf is one of the most beautiful "tunes" in the world. But U.S. scientists — oceanographers and seismologists — believe that it is not just the vibration, and only a fraction of a composite "voice" of the Earth. Put forward their hypothesis states that the interaction between the oceans and the atmosphere of the shelf creates a constant low-frequency vibrations, receiving a name — in infragravitatsionnyelny.
Ten years ago, researchers from the University of California discovered the existence of infrasonic background noise generated over the sea surface and spreading far enough inland. This acoustic wave with a frequency of 3.7 millihertz who can not hear or feel any person. Only by using ultrasensitive equipment, marine scientists were able to fix this vibration. Using data from seismic sensors around the world, two scientists from the University of California — Peter Bromirski and Peter Gershtoft — were able to locate its main sources. The epicenter of the most powerful "voice" of the Earth was recorded near the Pacific coast of Mexico, and the next power source turned off the west coast of Europe, writes sunhome.ru
Now, a decade later, at the disposal of scientists proved more powerful — a global network of seismological sensors USArray EarthScope. Located in the U.S. part of the global geological and geophysical program
has more than 400 sensors that allow you to register the most insignificant oscillations of the earth's crust. USArray unit was launched in 2003 and will continue until 2013. Forming its sensors are placed wide strip from north to south, so that the distance between them is less than 70 kilometers. For several months sensors receive and transmit seismic and tectonic information, after which they are transported and installed at the new location.
Mobile seismic shift from the U.S. Pacific coast to the east, and to the end of the period program
should collect data for a full seismic maps of North America. Obtained using USArray data showed that at the moment the most powerful source of the ground "voice" has moved north and is located near the Pacific coast of the U.S.. In the winter months, infrasound power increases significantly. Processing and analysis of all the results helped Oceanology and seismologists accurately articulate a theory of the origin of the world's "voice." The ocean surface is covered with ripples — water fluctuations with wavelength. This plays the role of a giant swell mediator between the air and water masses, supported by sustained infrasound vibrations.
When the swell reaches coastal areas, part of its energy through a complex nonlinear process is converted into infragravitatsionnye fluctuations with greater wavelength. It is these low-frequency tremors and recorded on the seismic stations, which are equipped with super-sensitive equipment.
Category: Scientists, experts, science