Missions

s part of the ERC ABYSS ("Megathrust Faults Monitoring from Abyssal Distributed Acoustic Sensing") project, we are looking for a postdoctoral fellow to work on temporal tracking of seismic wave velocity changes and plate interface imaging, using seismic doublets (repeaters) and microseismic noise recorded by Distributed Acoustic Sensing (DAS). This project aims to transform our observation capabilities of the giant subduction fault in Chile through the use of three DAS instruments, which over the past two years have been providing a continuous measurement of ground motion along more than 450 km of sub-optical fibermarine of the Chilean GTD network.

Activités

* Seismic velocity change monitoring =
To specifically target seismic velocity variations at the depth of the plate interface, we propose (1) to increase spatial resolution by using waves that probe these depths, such as seismic doublets, and (2) to identify and correct disturbances induced by other sources, such as oceanic or atmospheric variations, to improve our ability to detect signals that reveal hydromechanical conditions at the active structures. Any significant variation in seismic velocity will be interpreted together with the concomitant seismic activity anomalies, to give a complete picture of the underlying seismic processes. A preparatory work for this analysis will be to identify the repeaters in the seismic catalogue. Several swarms and main shock sequences – aftershocks in the La Serena area will be treated as a priority.

* High-resolution imaging =
We will use the 450 km of DAS measurements to produce models of crustal shear wave velocity, image and identify major seismically active structures in the plate contact area, as well as structural heterogeneities that lead to differences in the behavior of the subduction zone.

Compétences

• Proven experience (several years) in geophysical data analysis and visualization, signal processing, and ideally machine learning. • Practical knowledge of distributed acoustic detection (DAS) and its applications in seismology (valued asset). • Ability to work as a team and collaborate effectively with other researchers. • Communication skills, both oral and written, including the writing of scientific reports and presentation of results. • Flexible attitude and versatile mind, essential to meet unforeseen challenges and seize opportunities that arise in an exploratory project.

Contexte de travail

The Géoazur laboratory is a mixed multidisciplinary research unit composed of geophysicists, geologists and astronomers uniting around major scientific issues: telluric hazards (seismic, gravity and tsunami) and associated risks, the dynamics of the lithosphere and Earth imaging, the geodesy-metrology of the Earth and the near Universe. It includes about 200 people (researchers, teachers-researchers, engineers, doctoral students...). It is spread over 2 sites: the Azur CNRS campus in Valbonne Sophia Antipolis and the site of Calern – Caussols of the Observatoire Côte d'Azur. The person recruited will join a dynamic group of scientists working on DAS, who are experts in the use of DAS data for multiple applications, especially for seabed seismology. In addition, the ABYSS project will offer very rich interactions with a group of about ten people on a wide range of seismic applications of DAS data.
The employer will be the Observatoire de la Côte d'Azur (OCA) and the workplace will be located at the site of Sophia Antipolis. The Observatoire de la Côte d'Azur (OCA) is a national public institution for higher education and administrative research (EPA). The OCA brings together and directs research activities in Earth and Universe sciences of the Azurean region through its joint unit of services, Galilée and its three multi-institutional research units (OCA, CNRS, UNS, IRD): Artémis, Géoazur and Lagrange. The OCA is a member of the ComUE Université Côte d'Azur founded on 27 February 2015.