Several physical processes and properties have been proposed to play a role in the nucleation and triggering of earthquakes, including fault frictional properties, structural heterogeneity, the presence of fluids, thermal effects, aseismic deformation, as well as static and dynamic stress changes. However, their relative significance and relevant spatial and temporal scales remain uncertain. Integrative modeling of earthquake source processes is critically needed to deliver transformative science that capitalizes on recent progress in seismic, geodetic, geologic, laboratory, and numerical studies.


To answer these questions, my research aim to develop and apply physics-based computational methods that can address the interplay between long-term tectonics and rapid and localized earthquake source processes, including multiple temporal scales (dynamic rupture, interseismic period/earthquake sequences, and tectonic deformation), multiple spatial scales (fault core, fault segment, and network), and multiple physical and chemical factors (fluid effects, metamorphic reactions, realistic geometry, and inelastic processes).

RESEARCH

How do earthquakes start?

How do slow-slip events and earthquakes interact in space and time?

Faults accommodate deformation with a variety of different mechanisms that vary in space and time. Slip phenomena outside earthquake rupture, which include transient creep, slow-slip events, and afterslip, are characterized by slip velocities that vary by many orders of magnitude, from a few millimeter per year to meters per second.


The spatial and temporal history of fault slip undoubtedly influences the location, timing, and size of future earthquakes. As such, I develop earthquake cycle models that simulate the behavior of fault systems over many earthquake cycles, which include periods of slow tectonic loading and aseismic slip, earthquake nucleation, coseismic rupture, and afterslip/postseismic relaxation processes that are essential to understanding the behavior of seismogenic faults.

How can pore fluids in fault zones affect and trigger slow-slip events and earthquakes?

Pore fluids, ubiquitous in nature, have profound effects on fault structures. Their presence, chemistry, and movement can dramatically alter the rheological properties of the bulk rocks, compressive stresses felt across faults, fault loading, and shear resistance of the slipping layers. At the same time, earthquakes also directly affect the hydrogeological structure: fault rock damage can create permeability pathways that heal after an earthquake and seismic waves can increase permeability even at great distance. A major challenge in earthquake physics is to incorporate a fully coupled hydro-seismological modeling over the entire temporal and spatial scales of deformation.


To address this challenge, I develope two-phase flow numerical models — which couples solid rock deformation and pervasive fluid flow — to investigate how crustal stress and fluid pressure evolve along fluid-bearing fault structures before and during slow-slip events and earthquakes. This unified numerical framework accounts for full inertial (wave) effects and fluid flow in a poro-visco-elasto-plastic compressible medium. This new method contributes to improve our understanding of earthquake source processes along fluid-bearing fault structures, and demonstrate that fluids play a key role in controlling the interplay between seismic and aseismic slip.

LUCA DAL ZILIO