Details of the Abstract
| Title of paper | Quick-clay Investigation using Radio-Magnetotelluric Method |
| List of authors | S. Wang1, M. Landrø1, M. Bastani2, K. Duffaut3, S. E. Johansen1 and R. A. Rørstadbotnen1 |
| Affiliation(s) |
1Centre for Geophysical Forecasting, Department of Electronic Systems, Norwegian University of Science and Technology, shunguo.wang@ntnu.no; martin.landro@ntnu.no; stale.johansen@ntnu.no; robin.a.rorstadbotnen@ntnu.no 2The Geological Survey of Sweden/Department of Earth Sciences, Uppsala University, mehrdad.bastani@sgu.se 3Equinor, kdu@equinor.com |
| Summary |
Recent years have seen a significant rise in quick-clay landslides in Nordic countries, notably in Alta, Gjerdrum, and Stenungsund, causing severe damage and fatalities. This study explores the use of geophysical methods, particularly the radio-magnetotelluric (RMT) technique, to analyze quick clay characteristics and behavior in these regions. The RMT method offers an advanced approach to investigating the electrical resistivity of subsurface structures, vital for identifying quick clay zones. The Rissa region in Norway serves as a focal point due to its historical quick-clay landslide and existing geophysical infrastructure. Following the devastating Rissa landslide in 1978, Norway initiated a comprehensive national quick clay mapping project, which this study builds upon. We also collected distributed acoustic sensing (DAS) data at Rissa, aiming to combine the two datasets for a thorough analysis. Geological investigations at Rissa indicate a straightforward stratigraphy with flat terrain and a 20-meter-thick marine clay layer. Quick clay layers, distinguished by their higher electrical resistivity compared to marine clays, are found within borehole samples. The study employs RMT to map these layers and examine the influence of seasonal variations on their properties. RMT data were collected along a 250-meter RMT profile with 10-meter station spacing using the Enviro_MT instrument in both summer and winter. Results reveal a four-layered model: unconsolidated sediment, marine clays, potential quick clays, and bedrock. Notably, seasonal variations affected resistivity models, with the marine clay layer appearing thicker in winter due to reduced freshwater, and potential quick clay pockets showing increased thickness in some areas. These findings demonstrate the effectiveness of RMT data in identifying resistivity changes at quick-clay sites due to seasonal variations. The velocity model inverted from DAS data indicates an increase in velocity with depth. However, it is hard to distinguish quick clays from marine clays in the velocity model. This research provides valuable insights into the dynamic distribution of quick clays and their seasonal behavior, with implications for infrastructure planning and disaster management in landslide-prone areas. The integration of RMT and DAS results offers a new perspective on studying and monitoring quick-clay landslides. |
| Session Keyword | 5.0 Monitoring: of GICs, environmental, tectonic and geomorphological hazards |
| File upload |
5.0_quick-clay_investigation_wang.pdf
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