Full-waveform automatic location of small seismic events using synthetic strain Green’s tensors in an underground mine
DOI:
https://doi.org/10.17159/Abstract
A reliable method to locate microseismic events is an important objective26 for routine mine seismic monitoring. We hence developed an algorithm that can
automatically and reliably locate an event from a single uniaxial trace. Recorded
seismograms consist of the direct P- and S-waves as well as the waves reflected off
the underground excavations. We take advantage of the extra complexity these
reflections introduce as they make the signal more unique. In our investigation we
cross-correlated unaltered synthetic seismograms against trial waveforms created
from a linear combination of appropriate waveforms from a library of numerically
calculated strain Green’s tensors. We use a single uniaxial synthetic seismogram
to invert for the source location, six moment tensor components and frequency.
The resulting cost functions are constructed as maximal correlations at each node
in the mine grid through the true source x -planes. This function is maximised by
Differential Evolution to simultaneously yield the source parameters. Sensitivity
tests such as shifting the mine plans and altering the background velocities of
the media are investigated to test the methods robustness. We contaminate the
data with 40% white noise to test the methods resolution against simulated real
recorded seismograms. In this paper the method is demonstrated using synthetic
data calculated with a realistic underground 3D velocity model. The synthetic model is then applied to a real event.
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Copyright (c) 2024 Sahil Brijraj, Suleman Moolla, Richard Lynch
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