12-24 months Post-Doc position in Seismology : cryo-seismology data analysis, array processing, vibration analysis, active and passive seismic imaging, ambient seismic noise

Place : Isterre Laboratory, Grenoble, France
 

Contract duration: 12 months extendable to 24 months
Required degree: doctorate
Welcome experiences: PhD Thesis or Post-Doc in seismology, seismic imaging, array processing and/or big data processing. Imaging and inversion techniques.

Funding: Ministry of Ecological Transition (secured) –

Assignments:

Develop tools to detect, characterize, monitor glacial and peri-glacial risks and permafrost slopes.

As part of a national program to acquire knowledge on glacial and peri-glacial risks, we wish to exploit seismic and seismological measurements collected at high altitude in the French Alps. The recruited person will take part in all or part of the following actions.

Action 1: study of microseismic activity on the scale of the Mont-Blanc massif (74). Identification, classification and characterization of surface events, including basal sliding of glaciers, rock falls and landslides, serac falls and avalanches.

Action 2: monitoring of resonance frequency above a glacial cavity, on the Tête Rousse glacier (74). The resonance frequency of the cavity has been identified and mapped, the value and intensity of the resonance peak is likely to vary with the evolution of the geometry of the cavity, and especially its filling. Monitoring for at least 2 years will be carried out, in correlation with meteorological data and readings from piezometric sensors in the glacier.

Action 3: monitoring the rigidity of a permafrost slope at risk of destabilization. The seismic background noise makes it possible to monitor the apparent seismic velocity of the ground on a daily basis, which can be extrapolated to the rigidity of the ground (in the absence of a major change in the water content). By linking variations in rigidity to environmental variations (temperature, frost, precipitation), an evaluation of the evolution of fracturing and/or ice content will be proposed. The objective will also be to evaluate the feasibility of using the seismic tool to identify a precursor signal to slope destabilization. This work will be carried out on the north face of Bellecôte (73)

Action 4: detection and characterization of glacial cavities or basal detachment. Within glaciers, the presence of glacial cavities (notably intra- or subglacial water pockets) generates a mechanical impedance contrast between the ice and the void or liquid water of the cavity. This results in the existence of a vibrational resonance frequency of the ice vault (superficial part accessible from the surface). A dense seismological network measurement campaign will be carried out on the Rosolin glacier in Tignes (73). The data will then be processed by spectral component ratio, and mapped.

Action 5: very high frequency seismic imaging on the Tête Rousse cavity (74). Setting up the experiment, supporting data processing and 3D imaging of the cavity using active seismic.

All these actions are relatively distinct and have shown their relevance to a number of geological objects in the past. But to date, they have not yet been carried out systematically on glacial and peri-glacial risks. The project is therefore at the interface between fundamental research and industrial innovation, and could lead to recommendations and proposals for monitoring methods (detection and characterization), monitoring and alerting, with the objective of operational control by design offices specializing in geophysics and natural risks. The candidate will have to participate in the writing of summaries and reports intended for scientists, but also for engineers and decision-makers.

Activities:

The work will include an activity to assist with instrumentation in the field, and an activity to analyze seismological and seismic data in the Savoie and Haute-Savoie massifs. The candidate:

1) will be comfortable with installing and maintaining equipment in the field (on glaciers and in high mountains)

2) will perform parametric inversion of resonance data to map the glacial cavity(ies)

3) will perform Background noise analysis and passive imaging

4) will analyze and map the Micro-seismicity, create a landslide database on the scale of the massif

5) will analyze the velocity variation and structure change based on seismic coda and background noise

6) will analyze the noise sources: mapping, location and characterization of water flows

7) will write scientific articles (in English), a methodological guide (for design offices) and an operational report for natural risk decision-makers.

SKILLS:

Processing and analysis of seismology data; imaging and inversion; mechanics and geophysics, with basic notions of glaciology.

Team work, field work, autonomy and initiative, project management. Optional: high mountain experience will be appreciated.

Work environment

The recruited person will join the “Fault Mechanics” team. The project team is made up of 4 researchers, 1 or 2 interns, and another post-doc or doctoral student. The PAPROG program, funded by the Ministry of Ecological Transition, brings together several laboratories (EDYTEM, ISTerre, IGE, INRAE) and state services such as RTM. Strong collaborations with these different institutions will be expected.

ISTerre is a Joint Research Unit of Grenoble Alpes University, CNRS, USMB, IRD and Gustave Eiffel University, located 1381 rue de la Piscine 38400 Saint-Martin d'Hères and on the Bourget du Lac Scientific Campus. It is part of the Observatory of Sciences of the Universe of Grenoble (OSUG) and the PAGE research center of the University Grenoble Alpes (UGA). Its workforce is around 300 people for an average annual budget of €7 million. It is organized around 9 research and service teams, the scientific objective being the physical and chemical study of planet Earth, particularly focusing on the couplings between observations of natural objects, experimentation and modeling. associated complex processes. ISTerre also carries out solid Earth observation missions, hosts and maintains national parks of geophysical instruments, as well as a data center.

Contact and application:

Send a CV and a motivation letter stating your points of interests and personal added value and research/career perspectives to:  Eric.larose@univ-grenoble-alpes.fr