arXiv subjects

Marta Perez-Gussinye

Publications and source records attributed to Marta Perez-Gussinye.

3 recordsLinked to original sources

arXiv2026

Variational Derivation of the Weak Form for Viscous Flows Involving Free Surfaces with Implications for Geodynamic Simulations

Geodynamic simulations involve solving the Stokes equations, where boundary conditions play a crucial role in governing internal dynamics and surface topography evolution. A common approach is to model the interface in contact with air as a free surface. This interface is stress-free and deforms in response to internal force balances, which is essential for understanding processes ranging from rifted margins to subduction. However, a free surface can introduce instabilities and oscillations in the numerical solution, commonly known as the "drunken sailor" instability, forcing the use of small time steps. Geodynamic models therefore often employ stabilization terms based on the gravitational effect of free-surface motion. To date, these terms have been derived primarily on a heuristic basis. Here, we apply variational calculus to the energy-minimization formulation of incompressible Stokes flow. Using the Gateaux derivative, we derive the complete weak form for a deforming free-surface domain and show that the stabilization terms arise naturally from the free-surface assumption. We consider the linear-viscosity case and identify two boundary-integral contributions: one associated with internal viscous deformation and the other with gravitational body force. Two benchmark cases demonstrate the consistency of the derived formulation with previously proposed stabilization approaches. Our results provide a mathematical foundation for the commonly used gravity stabilization and identify an additional viscous boundary contribution.

math.NA↗

arXiv2025

Interactions between syn-rift magmatism and tectonic extension at intermediate rifted margins

Intermediate rifted margins exhibit neither seaward dipping reflectors nor exhumed mantle at the continent-ocean transition (COT). Instead, they transition into normal-thickness, magmatic Penrose-type oceanic crust, and thus diverge from the classic magma-rich and magma-poor end-member models. However, several intermediate margins, such as the South China Sea (SCS), display detachment faulting similar to magma-poor margins and magmatic underplating typical of magma-rich ones. How tectonics and magmatism interact in these intermediate environments is poorly understood. Here we use 2D numerical models to demonstrate that the elevated initial geotherm inherited from prior plate subduction in the SCS explains several key observations: an early phase of wide rifting, subsequent localization onto core complexes with substantial footwall magmatic intrusions, and eventual formation of normal igneous oceanic crust at break-up. Thermal weakening caused by syn-rift footwall magmatic intrusions facilitates lower crustal ductile flow, promoting the development of rolling-hinge type detachment faults and exhumation of core complexes. These structures are associated with accelerated tectonic subsidence, which is later moderated by detachment-related doming, as observed in the SCS. Normal-thickness oceanic crust occurs after break-up, even under ultra-slow extension rates used in our simulations, highlighting the importance of inheritance in determining margin architecture, the spatio-temporal distribution of syn-rift magmatism, and the nature of the COT. This behavior contrasts sharply with magma-poor margins, where a cooler lithosphere and similar ultra-slow extension produce no syn-rift magmatism, leading instead to crustal embrittlement, mantle serpentinization and exhumation at the COT.

physics.geo-ph↗

arXiv2025

Tectonics controls hydration-induced rheological heterogeneities in ultraslow-spread oceanic lithospheres

At ultraslow, magma-poor spreading ridges, plate divergence is controlled by tectonics, with formation of detachment faults that expose variably serpentinized mantle rocks. Seismicity and the depth of seismic events in these environments are influenced by the degree of serpentinization, yet the nature and extent of deeper alteration remain poorly understood. This study uses a 2D visco-elasto-plastic model with thermodynamic calculations to explore the interaction between tectonics and hydration during ultraslow seafloor spreading. By coupling water availability and lithosphere hydration progress with active deformation, we reveal: (i) a tectonically controlled vertical extent of alteration along detachment faults; (ii) the preservation of amphibole-facies in exhumed serpentinized footwalls; (iii) significant lithospheric scale rheological heterogeneities due to variations in alteration mineral assemblages. We propose that tectonically controlled spatial variations in alteration play a key role in controlling earthquake depth distribution at mid-ocean ridges and associated transform faults and discuss the implications for seismogenesis in subduction zones.

physics.geo-ph↗