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FORECAST EARTHQUAKES USING ACOUSTIC EMISSION

Victorin Emilian Toader

Abstract

Microfracturing and rock deformation as effects of tectonic stress generates sounds called acoustic emission. Many reporting on the earthquakes say that first people hear a noise and then they feel the two shocks (P and S waves). How is this possible as long as the speed of sound is less than the P wave speed? This article gives an answer for these question. An earthquake is an effect of high tectonic stress in an area (hypocenter) and the last part of this process is the loss of elasticity of rocks followed by breaking and release of a great energy. Basically the seismic wave generates and carries on the acoustics. We record earthquakes using seismic equipment and pressure sensors (air and ground) in Vrancea (bending area of Romanian Carpathians Mountains). In both cases you can see the P and S waves but the sounds generated by cracks contain high frequencies that are attenuated rapidly and appear to several hours prior to the event. The sound depends on where you are registered (geological structure, seismic activity, soil, elasticity). Acoustic emission (AE) forecast earthquakes but we cannot evaluate the magnitude. We could have a big one or several small earthquake. AE is part of a multidisciplinary network that analyzes precursor phenomenon (atmospheric aerosols, ions, CO2, radon and clouds in relationship with temperature, humidity, atmospheric pressure, wind speed and direction, variations of the telluric currents, local magnetic field, infrasound, atmospheric electrostatic field, electromagnetic and seismic activity, radio waves propagation, and animal behavior). Our records indicate an intensity of sounds before earthquakes greater than 4.5R with 8 - 10 hours.

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DOI resolver: doi.org/10.5593/sgem2019/1.1/s05.100

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