Coseismic damage near active faults : a laboratory perspective
Event details
Date | 17.11.2017 |
Hour | 12:15 › 13:15 |
Speaker | Prof. Dr Mai Linh Doan, ISTerre, University of Grenoble, France |
Location | |
Category | Conferences - Seminars |
Abstract : Earthquakes are generated by the fast propagation of slip along active faults.The faults are not a pure sharp discontinuity but are borded by a damage zone, that witnessed the history of the fault growth, tectonics loading and previous earthquakes. The latter is of great interest for the study of previous earthquakes but it needs to be discriminated from static damage. That’s why we pioneered a series of experiments to find markers of dynamic damage.
To do so, several rocks were loaded with Split Hopkinson Pressure Bars. We found that at strain rate, crystalline rocks tend to fragment in finely grained rocks but the accumulated strain is so small that the initial rock structure is preserved. This is similar to the pulverised rocks found in the field.The high strain needed to create this pervasive diffuse damage suggest an exceptionally high strain rate shaking, which is important for seismic hazard assessment. By repeating loading, a similar phenomenon occurs, but the threshold is only reduced by half.
Besides being promising for paleoseismic studies, the study of dynamic damage reveals appealing properties for the coseismic damaged rocks, with a sharply reduced sonic velocity and a strongly enhanced permeability, which can strongly affect the hydromechanical properties of active faults.
Bio : Mai-Linh Doan is assistant professor at ISTerre, an Earth Sciences laboratory of Université Grenoble-Alpes. She majored in physics at ENS Paris and then switched to geophysics to works on the mechanics of active faults (PhD in IPG-Paris and postdoctoral stay at UCLA and UCSC). She combines in situ observation of the hydromechanics of fault zone through scientific drilling and borehole geophysics, with laboratory rock mechanics experiments. Especially, she works to identify how the dynamic loading of earthquakes can produce markers of dynamic damage that can be used as marker of previous large earthquakes.
Practical information
- General public
- Free
Organizer
- Prof. Dr Brice Lecampion & Prof. Dr Katrin Beyer
Contact
- Prof. Dr Marie Violay, LEMR François Passelègue, LEMR