Characterization of in-situ clay blocks in the Harmalière landslide using seismic and electric methods.

Many regions of the world are exposed to landslides in clay deposits, which pose major problems for land management and population safety. Landslide hazard assessment is then of crucial importance to prevent such events and requires a thorough understanding of the internal controlling factors. Earthflows/earthslides are very tricky to understand both structurally and kinematically speaking.

This internship deals with the characterization of in-situ decameter-size clay blocks in the Harmalière landslide (40km south of Grenoble) using seismic and electric methods. The main goal is to retrieve the geophysical parameters (Vp, Vs and electrical resistivity) to characterize in detail the different layers in order to better understand the geophysical properties of the landslide at the hectometer scale and to retrieve precursory marker of the rupture comparing these results and previous data set analysis. A particular attention will be paid to the problem of geophysical anisotropy, which may be significant in those deposits.

The scientific questions of this work are :
–  What are the properties of each layer ?
–  What is the influence of these properties and especially of the anisotropy on the geophysical response ?

The internship will include three main steps :
1) In-situ data acquisition on blocks.
2) Data Processing and retrieving of the geophysical parameters in different orientations.
3) Numerical modeling for understanding the landslide images.

This study will participate to a global project that aimed at understanding the rheology of the clays during landsliding and particularly to the solid-to-fluid transition. 

Supervisors :
Denis JONGMANS (denis.jongmans univ-grenoble-alpes.fr), Gregory BIEVRE (gregory.bievre univ-grenoble-alpes.fr) and sylvain FIOLLEAU (sylvain.fiolleau univ-grenoble-alpes.fr).