Coupled Seismogenic Geohazards in Alpine Regions (COGEAR)

Abstract eng:
COGEAR is an interdisciplinary natural hazard project to investigate short and long-term earthquake preparation processes as well as complex surface effects induced by seismic strong ground motion. It addresses tectonic processes and related variability of seismicity in space and time, earthquake forecasting and observation of possible short-term precursors, and modelling and observation of weak and strong ground motion as a result of complex source and path effects. In soils and rock, we study non-linear wave propagation phenomena and liquefaction, the long-term impacts of repeated earthquakes on slope stability through rock mass strength degradation, and the triggering of landslides; the potential of earthquake-induced snow avalanches is also be estimated. Our focus is on the physics of non-linear processes in relation to topography, geological disposition, water saturation and slope stability. The consequences of earthquakes will be evaluated through scenarios of direct seismic hazard and assessment of susceptibility to induced (secondary) effects. The Valais region in Switzerland, and specifically the area of Visp, as well as the Visper and Matter valleys, have been selected. In the past, the Valais has experienced every 100 years a magnitude 6 or larger event, with the last magnitude 6.1 earthquake in 1946. The region of Visp is hit by damaging earthquakes every 40 years (Intensity VI-VIII), with the last nearby event in 1960 reaching a macroseismic intensity of VIII. During all such events significant damage occurred from ground motion and different kinds of secondary phenomena such as liquefaction in the Rhone plain, slope instabilities and extended rock fall. Our integrated approach includes detailed field investigations, the development of new investigatory techniques, the development and application of numerical modelling techniques, and the installation of prototype multi-sensor monitoring systems. Such systems are planned for long-term operation and will include a continuous GPS and seismic network, a test installation for observing any earthquake precursors, and two test areas (Visp, St. Niklaus-Randa) for studying site-effects and non-linear surface phenomena as well as their interaction.

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