Localization of acoustic emission sources according to the data of a distributed system of combined receivers

The article relates to the field of non-destructive testing of the stress-strain state of rocks in seismically active regions using the acoustic-emission method. The studied rocks are the source of the signal. Long-term studies in Kamchatka show that geoacoustic emission signals are a combination of pulses of various amplitudes, duration (about 30-100 ms) and fill frequency (up to 10 kHz), with a steep front and a smooth decline. The pulse repetition rate varies from units per minute to several hundred per second, depending on the stress-strain state of the rocks. The article presents the results of an experiment to determine the distance to sources of high-frequency acoustic radiation generated in near-surface sedimentary rocks. An underwater distributed acoustic system installed in Mikizha lake in Kamchatka is used to record signals. Two combined receivers are used as sensors, recording sound pressure and three of its gradients, and one sound pressure receiver. The direction to the source of the geoacoustic signal recorded by each receiver is determined by vector-phase methods. After that, radiation sources are localized in two ways: by triangulation and by the difference in the arrival time of signals from spaced receivers (empirical implementation of the difference-range-measuring method). The features of the application of the methods are described, taking into account the design features of the registration system. During the experiment, the coordinates of more than 40 sources of geoacoustic emission were measured, and their spatial distribution was plotted. The measurement error was less than 0.5 m. The paper presents directions for further development of research to improve the accuracy of emission sources localization. This article is an expanded and revised version of the report of the same name, presented by the authors at the XIII international conference “Solar-terrestrial relations and physics of earthquake precursors” (September 25 – 29, 2023, Paratunka, Kamchatka).