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E. Brückl, M. Pregesbauer, S. Mertl:
"Seismic Activity of Deeply Creeping Rock Slopes";
Talk: XXI. Tectonomechanics Colloquium, Graz (invited); 2003-05-09 - 2003-05-10; in: "XXI.Tectonomechanics Colloquium", Graz (2003).

Deep creep of rock slopes is frequently observed in high mountain areas. Over a time span of some thousand years many of these slopes developed according the pattern of a "Sackung" and obtained a stable equilibrium at present. However, there are also examples of deep creep changing unexpectedly to a rapid and catastrophic sliding motion. Geological investigations and continuous geodetic observations supply essential information about deeply creeping rock slopes. However, a prediction of the future behaviour of a deeply creeping rock slope during a phase of accelerating movement is still not possible. Therefore, the intention of monitoring the seismic activity of deeply creeping rock slopes is to deepen the understanding of the process and to broaden the data basis for the prediction of a change from creep to rapid sliding.
During IDNDR several mass movements were investigated in Austria by geodetic (Brunner et. al., 2000), geophysical (Brückl, 2001) and remote sensing methods (Rott et. al., 2000). For the monitoring program we selected two of these rock slopes, which represent deep creep in an active and rather early state (Gradenbach, Carinthia and Hochmais-Atemskopf, Tyrol). Even there is no imminent danger, we cannot exclude a transition to a rapid and catastrophic rock slide for these slopes in future time. The two rock slopes are also monitored by geodetic methods by other organizations. The monitoring time we realized on the two rock slopes comprises a total of 30 d with up to 10 seismic stations contemporarely deployed. At an average about one event per day was detected and localized. Magnitudes and seismic moments of the events and their pattern in space-time will shown. Irreversible displacements associated with the seismic events are compared with the displacements measured by geodetic methods and the seismic efficiency is estimated. Up to now, the seismic monitoring program has been having the character of a pilot study. The extension to a long time monitoring including phases of accelerating movement is an essential task for the future.

References:
Brückl, E., 2001, Cause-effect models of large landslides. Natural Hazards, 23, Kluwer Academic Publishers, Netherlands, 291-314.
Brunner, F. K., Hartinger, H. and Richter, B., 2000, Continuous monitoring of landslides using GPS: a progress report. in Geophysical Aspects of Mass Movements, Bauer, S. J. and Weber, F. (Eds.), Austrian Academy of Sciences, 51-60.
Rott, H., Mayer, C. and Siegel, A., 2000, Monitoring slope motion and surface deformation by means of radar interferometry. in Geophysical Aspects of Mass Movements, Bauer, S. J. and Weber, F. (Eds.), Austrian Academy of Sciences, 75-88.

Project Head Ewald Brückl:
IDNDR19/03 - Monitoring