Curriculum Vitae

Research

My research is focused on numerical modeling of continental collision and subduction dynamics. For the numerical flow models I'm using I2VIS and I2ELVIS thermo-mechanical codes developed by T.Gerya (2003, 2007), and Underworld (Moresi, et al., 2007). 

I investigate style of post-subduction collisional orogens in either compressional (Alps, Himalayas) and extensional (Northen Apennines, Figure 1) settings, looking at topography and heat flux time evolution, maximum metamorphic (P-T) degrees recorded by exhumed rocks, structures, stress/strain/brittle-ductile maps (Faccenda et al., Lithos, 2008; Faccenda et al, EPSL, 2009).

Fig. 1 - Decoupled collision zone. Left coloumn: snapshots of the model evolution. Right coloumn: a) time evoltion of the 1D topographic profile. b) time evolution of the 1D heat flux profile. c) tectonic stress map; the colour scale reflects stress magnitude; short and long double arrows indicate the orientation of the maximun and minimum principal stresses, respectively. d) rheological map: blue is brittle, red is viscous.

One of the unsolved problems of subduction settings is how and to which extent slab hydration occurs. There is strong evidence that slab hydration occurs mainly at the trench outer rise in response to the bending of the oceanic plate, but the mechanism that allows sea water percolation down to mantle depth remained unclear for many years. We have found that slab bending produces strong variations of the tectonic pressure and formation of subhydrostatic pressure gradients. As a consequence, fluids are pumped downward and react with dry mafic and ultramifc rocks forming hydrated and serpentinized rocks (Faccenda et al., Nat. Geo., 2009). At intermediate-depths, slab dehydration during unbending favors fluid flow toward the inner portion of the slab characterized by tectonic underpressure, yielding to the formation of a double hydrated zone.

 

Fig. 2 - Numerical model of slab hydration occurring at the trench outer rise and dehydration at intermediate-depths with the formation of a double hydrated zone (from Faccenda et al., 2012, G3).

Fig. 3 - Schematic cartoon showing the relation between tectonic pressure and fluid flow in the slab (from Faccenda et al., 2012, G3).

The interpretation of shear-wave splitting above subduction zones has been controversial and none of the inferred models seems to be sufficiently complete to explain the entire range of anisotropic patterns registered worldwide. We have addressed thi sproblem through numerical modeling of rock deformation, mineral physics and seismic wave propagaiton. The anisotropy may originate from both the strain-induced lattice preferred orientation (LPO) of anisotropic upper mantle minerals (Figure 4) and the slab fabric due to: 1) the crystallographic preferred orientation of highly anisotropic hydrous minerals (serpentine and talc) formed along steeply dipping faults; 2) the preferential orientation of fluid-filled cracks forming at intermediate depths as the slab undergoes dehydration; 3) the larger-scale vertical layering consisting of dry and hydrated crust-mantle sections whose spacing is several times smaller than teleseismic wavelengths. or the  (Figure 5).

Fig. 4 - Development of upper mantle anisotropy induced by slab subduction. Only half symmetric model is shown. Each bar represent the seismic fast direction of crystal aggregates (70% ol - 30% opx). The lenght and color of the bars areproportional to the transverse isotropy estimatedfrom the agregate elastic tensor (from Faccenda and Capitanio, 2012, GRL).

Fig. 5 - Schematic cartoon showing how slab anisotropy may affect SKS shear waves travelling in the upper mantle (from Faccenda et al., 2008, Nature).

1. Faccenda M. and Capitanio, F. A. Seismic anisotropy around subduction zones: insights from three-dimensional modelling of upper mantle deformation and SKS splitting calculations. Geochem. Geophys. Geosyst.,
   10.1002/ggge.20055 (2013). [Reprint]
2.  Capitanio, F. A. and Faccenda, M. Complex mantle flow around heterogeneous subducting oceanic plates. Earth Planet. Sci. Lett., 353-354, 29-37 (2012). [Reprint]
   
3. Faccenda M. and Capitanio, F. A. Development of mantle seismic anisotropy during subduction-induced 3D flow. Geophys. Res. Lett., 39, doi:10.1029/2012GL051988 (2012). [Reprint]
4. Faccenda, M., T. V. Gerya, N. S. Mancktelow, and L. Moresi (2012), Fluid flow during slab unbending and dehydration: Implications for intermediate-depth seismicity, slab weakening and deep water recycling, Geochem. Geophys. Geosyst., 13, Q01010, doi:10.1029/2011GC003860. [Reprint]
5. Faccenda M., Mancktelow, N. S. Fluid flow during unbending: implications for slab hydration, intermediate-depth earthquakes and deep fluid subduction. Tectonophys. 494, 149-154 (2010). [Reprint]
6. Faccenda M., Gerya, T.V., Burlini L. Deep slab hydration induced by bending-related variation of the tectonic pressure. Nature Geoscience 2, 790-793 (2009). [Reprint]
7. Faccenda M., Minelli G., Gerya T.V. Numerical modeling of active advancing and retreating post-subduction collision controlled by rheological weakening of the subduction channel. Earth Plant. Sci. Lett. 278, 3-4, 337-349 (2009). [Reprint]
8. Faccenda M., Burlini L., Gerya T.V., Mainprice D. Fault-induced seismic anisotropy by hydration in subducting oceanic plates. Nature 455, 1097-1100 (2008). [Reprint]
9. Faccenda M., Gerya, T.V., Chakraborty, S. Styles of post-subduction collisional orogeny: Influence of convergence velocity, crustal rheology and radiogenic heat production. Lithos 103, issue 1-2, pp. 257-287, doi: 10.1016/j.lithos.2007.09.009 (2008). [Reprint]
10. Faccenda M., Bressan G., Burlini L. Seismic properties of the upper crust in the central Friuli area (northeastern Italy) based on petrophysical data. Tectonophys.  445, issue 3-4, 210-226, doi:10.1016/j.tecto.2007.08.004 (2007). [Reprint]

Corso di Modellizzazione numerica nelle geoscienze