1,721,144 research outputs found
Numerical models of slab migration in continental collision zones
No full text""\\"Continental collision is an intrinsic feature of plate tectonics. The closure of an oceanic basin leads to the onset of subduction of buoyant continental material, which slows down and eventually stops the subduction process. In natural cases, evidence of advancing margins has been recognized in continental collision zones such as India-Eurasia and Arabia-Eurasia. We perform a parametric study of the geometrical and rheological influence on subduction dynamics during the subduction of continental lithosphere. In our 2-D numerical models of a free subduction system with temperature and stress-dependent rheology, the trench and the overriding plate move self-consistently as a function of the dynamics of the system (i.e. no external forces are imposed). This setup enables to study how continental subduction influences the trench migration. We found that in all models the slab starts to advance once the continent enters the subduction zone and continues to migrate until few million years after the ultimate slab detachment. Our results support the idea that the advancing mode is favoured and, in part, provided by the intrinsic force balance of continental collision. We suggest that the advance is first induced by the locking of the subduction zone and the subsequent steepening of the slab, and next by the sinking of the deepest oceanic part of the slab, during stretching and break-off of the slab. These processes are responsible for the migration of the subduction zone by triggering small-scale convection cells in the mantle that, in turn, drag the plates. The amount of advance ranges from 40 to 220 km and depends on the dip angle of the slab before the onset of collision.\\""
How collision triggers backarc extension: insight into Mediterranean style of extension from 3-D numerical models
Full text linkThe formation and evolution of a backarc basin are linked to the dynamics of the subduction system. The opening of the central Mediterranean basins is a well-documented example of backarc extension characterized by short-lived episodes of spreading. The underlying reasons for this episodicity are obscured by the complexity of this subduction system, in which multiple continental blocks enter the subduction zone. We present results from three-dimensional numerical models of laterally varying subduction to explain the mechanism of backarc basin opening and the episodic style of spreading. Our results show that efficient backarc extension can be obtained with an along-trench variation in slab buoyancy that produces localized deformation within the overriding plate. We observe peaks in the trench retreating velocity corresponding first to the opening of the backarc basin, and later to the formation of slab windows. We suggest that the observed episodic trench retreat behavior in the central Mediterranean is caused by the formation of slab windows
The role of the lithospheric stiffness and plate ageing on trench kinematics: insights from numerical models
No full textOn the relation between trench migration, seafloor age, and the strength of the subducting lithosphere
No full textOceanic lithosphere thickens and strengthens as it grows older. Worldwide databases reveal that the age of the slab to a certain extent
controls the subduction style. Old and thick (and consequently strong) slabs show a trench “advance,” while younger, thin (weak) slabs are
migrating in retreating style (trench “rollback”). We performed numerical models to show that this confi guration could be the result of the
dynamic equilibrium between gravity and resisting forces. In particular we show that energy dissipation caused by bending and unbending
of the slab, although less important than other resisting forces, could be a primary control on trench migration. Our results fi t well with
global compilations of kinematic data from modern subduction zones in two reference frames with different amounts of net rotations. Based
on the age at which the transition from retreating to advancing style occurs, we propose an effective lithosphere/mantle viscosity of ~200
during bending of the lithosphere into the subduction zone
On the relation between trench migration, seafloor age and the strength of the subducting lithosphere
No full text
Modelling fluid flow in complex natural fault zones. Implications for natural and human-induced earthquake nucleation
Full text linkPore fluid overpressures in active fault systems can drive fluid flow and cause fault weakening and seismicity. In return, deformation accommodated by different modes of failure (e.g. brittle vs. ductile) also affects fault zone permeability and, hence, fluid flow and pore fluid pressure distribution. Current numerical simulation techniques model how fluid flow controls fault reactivation and associated seismicity. However, the control exerted by pore fluid pressure on the transition from slow aseismic fault sliding to fast seismic sliding, during the earthquake nucleation phase, is still poorly understood. Here, we model overpressured, supercritical CO2 fluid flow in natural faults, where non-linear, complex feedback between fluid flow, fluid pressure and fault deformation controls the length of the nucleation phase of an earthquake and the duration of the interseismic period. The model setup is an analogue for recent seismic source events in the Northern Apennines of Italy (e.g. Mw 6.0 1997-98 Colfiorito and Mw 6.5 2016 Norcia earthquakes). Our modelling results of Darcy fluid flow show that the duration of the nucleation phase can be reduced by orders of magnitude, when realistic models of fault zone architecture and pore pressure- and deformation-dependent permeability are considered. In particular, earthquake nucleation phase duration can drop from more than 10 years to a few days/minutes, while the seismic moment can decrease by a factor of 6. Notably, the moment of aseismic slip (M0=109Nm) obtained during the nucleation phase modelled in our study is of the same order as the detection limit of local strain measurements using strain meters. These findings have significant implications for earthquake early warning systems, as the duration and moment of the nucleation phase will affect the likelihood of timely precursory signal detection. Interestingly, aseismic slip has been measured up to a few months before some recent large earthquakes, although in a different tectonic context than the model developed here, rekindling interest in the nucleation phase of earthquakes. In addition, our results have important implications for short and long term earthquake forecasting, as crustal fluid migration during the interseismic period may control fault strength and earthquake recurrence intervals
Analogue modelling of plate rotation effects in transform margins and rift-transform intersections.
No full textRaw data for the manuscript titled "Analogue modelling of plate rotation effects in transform margins and rift-transform intersections." to the AGU journal Tectonics.Farangitakis, G.-P., Sokoutis, D., McCaffrey, K. J. W., Willingshofer, E., Kalnins, L. M., van Hunen, J., & van Steen. (2018). Analogue modelling of plate rotation effects in transform margins and rift-transform intersections. [Data set]. Zenodo. https://doi.org/10.5281/zenodo.132123
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