[Back]

S. Weginger:
"Detektion und Lokalisierung seismischer Signale zur Uberwachung der Massenbewegung Steinlehnen";
Supervisor: E. Brückl, S. Mertl; Institut für Geodäsie und Geophysik, 2012.

In spring 2003 there was a reactivation of the deep-seated gravitational
creep Steinlehnen (Tyrol, Austria). The result was an acceleration
of the mass movement associated with an increase of rockfall activities.
Immediately a temporary evacuation of the nearby settlements
and a roadblock was necessary. Permanent protection devices and the
installation of a monitoring system of the slope were initiated.
The mass movement consists of an highly active slap which is embedded
within a large area of the deep-seated gravitational creep. The
active slap has a size of 400 x 200 m with a thickness of up to 20 m. It
shows displacement rates of 15 cm per year and episodic accelerations.
In summer 2010 a seismic monitoring network on the slope was installed
again. At the same time a geodetic monitoring system of the
TU Darmstadt with a Syntetic Aperature Radar (GBSAR) was operating.
It provided every 7 minutes a high resoltion di_erence image
of the surface of the slope. During the observation period an increase
of the displacement rate of 70 mm within a few days took place again,
accompanied by rockfall activities. The monitoring system recorded a
large number of seismic events of various origins and intensities. The
most obvious signals caused by events on the surface such as rockfalls
and gravel avalanches could be determined in combination with the
radar images.
By determining signal descriptive parameters an objective classi_cation
algorithm was developed to distinguish between di_erent types
of events. The localization of the sources of seismic signals allows an
assignment to the mass movement. There is a correlation between
the geodetic measurements of movement rates and the seismic energy
emitted from the mass movement. The di_erent event classes show a
di_erent curve of the cumulative seismic energy. The maximum activity
of one class takes place even before the acceleration of the mass
movement. It shows the behavior of a precursor.

http://publik.tuwien.ac.at/files/PubDat_230256.pdf