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| Titel |
High-resolution seismic monitoring of rockslide activity in the Illgraben, Switzerland |
| VerfasserIn |
Arnaud Burtin, Niels Hovius, Michael Dietze, Brian McArdell |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250098562
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| Publikation (Nr.) |
 EGU/EGU2014-14251.pdf |
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| Zusammenfassung |
| Rockfalls and rockslides are important geomorphic processes in landscape dynamics. They
contribute to the evolution of slopes and supply rock materials to channels, enabling fluvial
incision. Hillslope processes are also a natural hazard that we need to quantify and, if
possible, predict. For these reasons, it is necessary to determine the triggering conditions and
mechanisms involved in rockfalls. Rainfall is a well-known contributor since water, through
soil moisture or pore pressure, may lead to the inception and propagation of cracks and can
induce slope failure. Water can also affect slope stability through effects of climatic
conditions such as the fluctuations of temperature around the freezing point. During the
winter of 2012, we have recorded with a seismic array of 8 instruments substantial rockslide
activity that affected a gully in the Illgraben catchment in the Swiss Alps. Three stations
were positioned directly around the gully with a nearest distance of 400 m. The
period of intense activity did not start during a rainstorm as it is common in summer
but during a period of oscillation of temperatures around the freezing point. The
activity did not occur in a single event but lasted about a week with a decay in time
of the event frequency. Many individual events had two distinct seismic signals,
with first, a short duration phase of about 10 s at frequencies below 5 Hz that we
interpret as a slope failure signature, followed by a second long duration signal
of > 60 s at frequencies above 10 Hz that we attribute to the propagation of rock
debris down the slope. Thanks to the array of seismic sensors, we can study the fine
details of this rockslide sequence by locating the different events, determining their
distribution in time, and systematic quantification of seismic metrics (energy, duration,
intensity-¦). These observations are compared to independent meteorological constrains
and laser scan data to obtain an estimate of the volume mobilized by the event. |
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