Temperature dependence of acoustic emission from impact fractured granites

• Energy distributions in AE time series from fracturing granites were constructed.
• Sample temperature varied from 20 °C to 600 °C.
• Energy distributions followed the power law in the range 20 °C to 300 °C.
• The b-value exhibited a trend to decrease with the increase of the temperature.
• Energy distributions followed the exponential law in the range 400 °C to 600 °C.

Pre-failure damage accumulation in deformed rock as well as crack propagation in fracturing geomaterials is accompanied with the generation of elastic (acoustic) waves. These processes are similar in main features in tectonic formations and under laboratory conditions. Therefore, the data obtained in acoustic emission (AE) experiments are widely used for interpreting some trends in natural seismic processes. However, the laboratory experiments on rock loading are usually performed at room temperature, while the temperature of geostructures at the depth of faulting can reach a few hundred degrees. In this communication, we present results of the AE study of impact-induced damage in granites of two grain sizes performed at different temperatures. The energy release distributions in AE time series (dependences of event number on event energy) were found to follow the Gutenberg–Richter type relation in the temperature range 20 °C to 300 °C; the b-value in this range showed a trend to decrease with the increase of the sample temperature. At higher temperatures (up to 600 °C), the energy distributions exhibited the Poissonian-type (exponential) behavior, thus evidencing the stochastic character of the process. The distributions of time intervals between successive pulses exhibited the same trend but less pronounced.