Single-block rockfall dynamics inferred from seismic signal analysis
Seismic monitoring of mass movements can significantly help to mitigate the associated hazards; however, the link between event dynamics and the seismic signals generated is not completely understood. To better understand these relationships, we conducted controlled releases of single blocks wit...
Main Authors: | , , , , , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2017-05-01
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Series: | Earth Surface Dynamics |
Online Access: | http://www.earth-surf-dynam.net/5/283/2017/esurf-5-283-2017.pdf |
Summary: | Seismic monitoring of mass movements can significantly help to
mitigate the associated hazards; however, the link between event dynamics and
the seismic signals generated is not completely understood. To better
understand these relationships, we conducted controlled releases of single
blocks within a soft-rock (black marls) gully of the Rioux-Bourdoux torrent
(French Alps). A total of 28 blocks, with masses ranging from 76 to 472 kg, were used
for the experiment. An instrumentation combining video cameras and
seismometers was deployed along the travelled path. The video cameras allow
reconstructing the trajectories of the blocks and estimating their velocities
at the time of the different impacts with the slope. These data are compared
to the recorded seismic signals. As the distance between the falling block
and the seismic sensors at the time of each impact is known, we were able to
determine the associated seismic signal amplitude corrected for propagation
and attenuation effects. We compared the velocity, the potential energy lost,
the kinetic energy and the momentum of the block at each impact to the true
amplitude and the radiated seismic energy. Our results suggest that the
amplitude of the seismic signal is correlated to the momentum of the block at
the impact. We also found relationships between the potential energy lost,
the kinetic energy and the seismic energy radiated by the impacts. Thanks to
these relationships, we were able to retrieve the mass and the velocity
before impact of each block directly from the seismic signal. Despite high
uncertainties, the values found are close to the true values of the masses
and the velocities of the blocks. These relationships allow for gaining a better
understanding of the physical processes that control the source of high-frequency
seismic signals generated by rockfalls. |
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ISSN: | 2196-6311 2196-632X |