PhD position: gradiometric sensors for high-resolution seismic imaging using sparse recording configurations

100%, Zurich, fixed-term

Seismic waves allow us to image the Earth's sub-surface. This approach, originating in the field of exploration geophysics, is also gaining an increased interest in the sub-surface characterization of planetary bodies in our solar system. A shortcoming of seismic imaging is that the resolution is limited by the number of sensors, due to a signal processing principle known as the sampling theorem. While it may be relatively straightforward in Earth-based applications to add more sensors to obtain better images, deploying large-sensor arrays on the Moon or Mars is not. This forces us to think of ways to obtain the most information out of a sparse network of available sensors.

The Institute of Geophysics is looking for a PhD student. We are flexible with respect to the starting date but it should be no later than September 2023.

Project background

One potential approach around the sampling theorem is so-called generalized sampling. In generalized sampling, we compensate for the lack of recording locations by using information on the spatial derivatives of the seismic wave field. A ‘gradiometric sensor’ is a device capable of measuring such spatial derivatives. However, being a novel approach, there are no established designs for gradiometric sensors.  We want to solve this shortcoming using metamaterials — novel structures that present advanced wave control capabilities due to their precisely-controlled microstructure. Metamaterials can focus the sound at very small locations, route waves around objects or expand horizontally when elongated. In this project, we will use these properties to make gradiometric sensors, by designing a metamaterial structure so that it passively senses (combinations of) spatial derivatives of the seismic wave field. The derivatives will be converted to an electrical signal using a custom-made Micro Electro Mechanical System (MEMS) transducer.

Job description

In the Exploration and Environmental Geophysics (EEG) group at ETH Zürich, we are recruiting a PhD student to design, fabricate and test gradiometric sensors, based on mechanical metamaterials. You will involve a combination of theory and experiments. The theory work will comprise computer optimization of the sensor design whereas the experimental part will consist of the fabrication and characterization of the sensor. For fabrication, we will employ a combination of 3D printing and cleanroom-based microfabrication, and for characterization, we will use laser doppler vibrometry on a sandbox setup for instance containing lunar regolith simulant.

This project has a strong international component. You are expected to spend one year at AMOLF (Amsterdam) working on the sensor/metamaterial design, and several months at EPFL in Lausanne for device fabrication. The home base will be at the Centre for Immersive Wave Experimentation (CIWE) at ETH Zurich, where the laser/sandbox characterization setup is located. The resulting concept sensor will be part of a proposal for a lunar mission expected to take place in 2026.

Your profile

• MSc in Geophysics, Physics, Mechanical or Electrical Engineering, Material Science
• Strong interest and training in one or more of: physics of wave propagation, meta-materials, numerical modeling and optimization
• Strong interest in laboratory experimentation and fabrication
• Independent yet likes to work in a team   

Your workplace

Your workplace

We offer

ETH Zurich is a family-friendly employer with excellent working conditions. You can look forward to an exciting working environment, cultural diversity and attractive offers and benefits.

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Curious? So are we.

We look forward to receiving your online application by 28.02.2023 with the following documents:

• Certified copies of diplomas
• Certified copies of grade certificates
• Curriculum Vitae (CV)
• Cover letter

Please note that we exclusively accept applications submitted through our online application portal. Applications via email or postal services will not be considered.

Further information about the Institute of Geophysics and the Exploration and Environmental Geophysics group can be found on our website . Questions regarding the position should be directed to Prof. Johan Robertsson, Prof. Marc Serra-Garcia, and Dr. Dirk-Jan van Manen, email: [email protected] (no applications).

About ETH Zürich

ETH Zurich is one of the world’s leading universities specialising in science and technology. We are renowned for our excellent education, cutting-edge fundamental research and direct transfer of new knowledge into society. Over 30,000 people from more than 120 countries find our university to be a place that promotes independent thinking and an environment that inspires excellence. Located in the heart of Europe, yet forging connections all over the world, we work together to develop solutions for the global challenges of today and tomorrow.