Dr. Alexander Rösner

My research covers a wide range of geohazard-related phenomena, e.g., earthquake nucleation & propagation, submarine landslides, and tsunamis. I am involved in three projects scattered around the world:

• Lake Lucerne (Switzerland)
• offshore Nice (France)
• offshore the Kii peninsula (Japan – Kumano drilling transect)

These study areas have a long record of historically documented geohazards, causing casualties and infrastructural damage to the nearby coast. By combining various methods such as geophysical in-situ measurements, coring, laboratory experiments, and long-term observations, the overall goal is to better understand geohazards' physics.

Lake Tsunamis: Causes, Controls, and Hazard - Lake Lucerne (Singeria Project)

The project aims at unraveling the trigger mechanisms, preconditions, processes, and impacts of lake tsunamis, a so-far underexplored natural hazard. General tsunami research has traditionally focused on the large ocean megatsunamis; however, historic chronicles document clearly that waves of similar heights also occur on lakes, potentially causing widespread coastal damage and even casualties. With a detailed historical database and its extensive previous limnogeologic and paleoseismic research, Central Switzerland offers an outstanding field laboratory to assess the relevant lake-tsunami processes. Results are anticipated to be applicable to other lake districts, and as added bonus, the gained knowledge of underlying processes will contribute to a better general understanding of mass-movement induced tsunami waves in the marine realm

Slope Stability - offshore Nice

The shallow Nice submarine slope is notorious for the 1979 tsunamigenic landslide that caused casualties and severe infrastructural damage. It is most likely one of the best-studied submarine landslides in the world. Nevertheless, the trigger mechanism for the slide was never resolved undoubtedly. Furthermore, the risk potential for future submarine landslides, e.g., triggered by earthquakes, high river discharge, and changing sedimentation patterns, is not well understood. I am working on a slope stability study assessing the slope stability offshore Nice during an Mw ~6 earthquake.

Earthquake Mechanics - Kumano Drilling Transect offshore Japan

The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE); a multi expedition International Ocean Discovery Program (IODP) drilling project offshore Japan, was designed to investigate fault mechanics and seismogenesis along the Kumano Transect offshore the Kii Peninsula. For 1300 years, devastating tsunamigenic earthquakes are documented for the Nankai Trough with recurrence intervals of 90 – 150 years. In the last century, two megathrust earthquakes 1944 Tonankai (Mw 8.1) and 1946 Nankaido (Mw 8.3), nucleated in the Nankai Trough. I am using core samples from different fractures zones in the Nankai Trough subduction zone to evaluate the velocity dependency of frictional behavior of preexisting fault and wall rock. Moreover, my project incorporates pressure and temperature data time series measured in various boreholes along the Nankai Trough. Based on this data, long-term transients can be analyzed.

In the projects mentioned above, I am using various tools, methods, and experiments.

• Deep-sea observatories
• Long-term pressure and temperature monitoring
• Time series analysis
• Seismic imaging
• Bathymetry
• Coring (gravity coring, piston coring, drilling)
• Geotechnical experiments, e.g., Triaxial, Rotary shear, and Direct shear experiments
• Velocity step and Slide-Hold-Slide friction experiments
• and many more …