Revealing interior structure of planetary bodies from their tidal response

In particular, recent developments in seismology resulted in advanced global crust and mantle seismic velocity models. However, seismic data is known to be poorly sensitive to density structure, which is key for fields like geodynamics and geodesy, as it drives mantle convection and shapes the geoid. Consequently, additional methods are required to constrain the density structure. Tidal phenomena are ubiquitous in the universe. On Earth, tidal forces lead to periodic deformations by directly distorting solid components, as well as causing secondary deformations due to the weight of ocean tides — a process known as ocean loading tides. Tidally induced deformations are characterized by unique temporal and spatial frequencies, making tidal response an important complementary information, reflecting interior properties. In this study, we investigate the sensitivity of the ocean tidal loading response to the Earth's interior structure, with a primary focus on density. We examine the influence of common three-dimensional effects, such as surface topography, crustal thickness, and heterogeneous mantle structure on the tidal response and compute sensitivity kernels with respect to elastic parameters and density. To achieve this, we implemented an advanced numerical approach based on the high-order spectral element method. In the second part, we investigate the body tide deformation of Phobos, the innermost satellite of Mars. The origin of Phobos remains enigmatic, and to advance our understanding, more information about its interior is needed. We explore what constraints the body tide response can provide regarding Phobos' internal structure. The numerical framework and methods developed in this thesis are widely applicable to study tidal deformations. They also lay the foundations for inferring material properties from tidal observations using the adjoint method. We therefore expect numerous directions for follow-up research. For instance, in addition to the case studies on Earth and Phobos presented here, we have started studies involving atmospheric loads on Venus and body tides on Moon.

Grantor dc:publisher

ETH Zurich

Year dc:date

2025

Author dc:creator

• Dmitrovskii , Andrei

Contributors dc:contributor

• Fichtner, Andreas
• Böhm, Christian
• Khan, Amir
• Lau, Harriet
• Martens, Hilary

• Tides, Earth's interior structure, Tidal tomography
• Earth sciences

Statement dc:rights

• info:eu-repo/semantics/openAccess
• Creative Commons Attribution 4.0 International

Licence

• http://creativecommons.org/licenses/by/4.0/

Language dc:language

en

Identifier

https://doi.org/10.3929/ethz-c-000796329

OAI identifier oai:identifier

oai:www.research-collection.ethz.ch:20.500.11850/796329