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| Titel |
Pre-failure behaviour of an unstable limestone cliff from displacement and seismic data |
| VerfasserIn |
J.-L. Got, P. Mourot, J. Grangeon |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Science ; 10, no. 4 ; Nr. 10, no. 4 (2010-04-15), S.819-829 |
| Datensatznummer |
250008085
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| Publikation (Nr.) |
 copernicus.org/nhess-10-819-2010.pdf |
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| Zusammenfassung |
| We monitored the displacement and seismic activity of an unstable vertical
rock slice in a natural limestone cliff of the southeast Vercors massif,
southeast France, during the months preceding its collapse. Displacement
measurements showed an average acceleration of the movement of its top, with
clear increases in the displacement velocity and in the discrete seismic
event production rate during periods where temperature falls, with more
activity when rainfall or frost occurs. Crises of discrete seismic events
produce high amplitudes in periodograms, but do not change the high frequency
base noise level rate. We infer that these crises express the critical crack
growth induced by water weakening (from water vapor condensation or rain) of
the rock strength rather than to a rapid change in applied stresses. Seismic
noise analysis showed a steady increase in the high frequency base noise
level and the emergence of spectral modes in the signal recorded by the
sensor installed on the unstable rock slice during the weeks preceding the
collapse. High frequency seismic noise base level seems to represent
subcritical crack growth. It is a smooth and robust parameter whose
variations are related to generalized changes in the rupture process. Drop of
the seismic noise amplitude was concomitant with the emergence of spectral
modes – that are compatible with high-order eigenmodes of the unstable rock
slice – during the later stages of its instability. Seismic noise analysis,
especially high frequency base noise level analysis may complement that of
inverse displacement velocity in early-warning approaches when strong
displacement fluctuations occur. |
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