Talks and Poster Presentations (with Proceedings-Entry):
E. Brückl, S. Mertl:
"Seismic Monitoring of Deep-Seated Mass Movements";
- 2006-09-29; in: "Disaster Mitigation of Debris Flows, Slope Failures and Landslides",
Universal Academic Press, Inc. Tokyo, Japan,
Deep-seated mass movements in crystalline rock start frequently with internal deformation comprising the whole rock mass. In an advanced state deformation concentrates to one or several shear zones. The surface velocities remain still in the range of 0.01 - 1 m/year and the deformation process can be classified as creep. Most of these mass movements stabilize after a displacement of the center of gravity in the range of 100-300 m. However, a few examples exist that transformed from creep to rapid sliding. This transition can be equivalent to a catastrophic event. State and velocity dependent friction laws can explain this behavior. A fully developed basal shear plane is prerequisite for a transition from creep to rapid sliding. The only observational indication of such an event is approximately exponential increasing velocity. Additional observational quantities related to the development of deep-seated mass movements would be very helpful to support prediction. The mass movements we consider take place in brittle rock and are expected to produce fractures or to display stick-slip movement on existing shear planes. Both processes generate seismic energy. Information that can be gained from monitoring and analyzing this seismic activity is manifold. Focal coordinates tell where brittle deformation takes place and other seismic parameters may be related to the state of the mass movement.
Since 2001 several passive seismic monitoring campaigns were carried out on three deep-seated mass movements (saggings) in the Eastern Alps in Austria: Gradenbach (Schober Range, Carinthia), Hochmais-Atemskopf (Ötztaler Alpen, Tyrol), and Niedergallmig-Matekopf (Samnaun Range, Tyrol). Different recording systems have been used, mostly with 3C-seismometers, natural frequency 4.5 Hz. Up to 11 stations operated simultaneously on one mass movement. Since September 2004 also one broadband seismometer has been operating continuously on Gradenbach. The seismic events produced by the mass movements and recorded by our monitoring system have frequency contents (above noise level) up to 30 Hz, durations of 5s to 20 s, and magnitudes MW of -2 to 0. Several automated event detection and localization methods are under development. We will present the results we achieved so far. A characterization of the observed seismic activity related to status and velocity of each mass movement will be attempted.
deep-seated mass movement, creep, seismic activity, instability, prediction
Electronic version of the publication:
Project Head Ewald Brückl:
IDNDR19/03 - Monitoring
Created from the Publication Database of the Vienna University of Technology.