Alexis Sáez

Welcome! I am a postdoctoral researcher in the Division of Geological and Planetary Sciences at Caltech, working with Prof. Jean-Philippe Avouac and Prof. Ares Rosakis (from the Division of Engineering and Applied Science). Before coming here, I obtained my PhD in Geomechanics from the École Polytechnique Fédérale de Lausanne (EPFL), where I was advised by Prof. Brice Lecampion, and did a short postdoctoral research stay with Prof. Dmitry Garagash at Dalhousie University.

Broadly speaking, my research aims to understand how geological faults respond to tectonic and anthropogenic forcing, and how fluids interact with the Earth’s crust. I am particularly interested in simple yet fundamental questions: How do earthquakes start and stop? How do fluids influence fault slip and earthquake occurrence? Using tools from theoretical, computational, and experimental mechanics (solid and fluid), I develop and test physics-based models to explain geophysical and geological observations of the Earth. Through this approach, I seek to advance our understanding of the physics of rock-fluid interactions, faults, and earthquakes, as well as the associated natural and human-induced hazards that affect our societies.

During my PhD, I worked primarily on fluid-driven frictional ruptures and their applications to injection-induced seismicity, a key challenge for the safe deployment of geo-energy technologies that are critical to the decarbonization of our energy systems, such as deep geothermal energy and geological CO₂ storage. While I continue to work on and collaborate in these areas, my current research focuses largely on other fundamental problems in earthquake science. In particular, I am investigating the physical mechanisms that control:

• Fault segmentation patterns observed in historical and paleoseismic records along major plate-boundary faults
• The connection between metamorphic dehydration reactions and slow earthquakes in subduction zones
• The spatio-temporal dynamics of earthquake swarms in fluid-rich environments and fault networks
• The timing of earthquake nucleation
• Fluid transport and fault-slip processes in faults that lose fluid to their country rock

Through collaborations, I also help to investigate:

• The role of elastic interactions within fault systems in generating the synchronization and alternation patterns observed in earthquake sequences in the geologic record
• Fault opening and slip induced by pore-fluid pressure transients
• The factors controlling the maximum magnitude of reservoir-depletion-induced earthquakes
• Earthquake triggering associated with mining and hydraulic fracturing operations
• And beyond Earth, hydrochemical processes that may explain the possible presence of water in the middle crust of Mars