Lithosphere density model in Italy: no hint for slab pull

Abstract

The lithosphere–asthenosphere system of the Italic region in terms of shear-velocity and density distribution with depth is suitable to investigate the geodynamic context of the region. The velocity structure is obtained through nonlinear inversion of dispersion curves compiled from surface wave tomography on cells 1° × 1° and a smoothing optimization method to choose the representative cellular model, whose layering is used as fixed (a priori) information to obtain a density model by means of linear inversion of gravimetric data. Seismicity and heat flow are used as independent constraints in outlining both the crustal and the seismic lid thickness; the nonlinear moment tensor inversion of recent damaging earthquakes allows some insight in the ongoing kinematic processes. Asymmetry between west-directed (Apennines) and east-directed (Alps, Dinarides) subductions is a robust feature of the velocity model, while density model reveals that slabs are not denser than the ambient mantle, thus supplies no evidence for slab pull

Seismic waves in 3-D: from mantle asymmetries to reliable seismic hazard assessment

“…Following this procedure, it has been shown in several cases that the LVZ does not correspond to a low-density zone, and thus, it is gravitationally stable (e.g. Brandmayr et al 2011;Zhang et al 2014).…”

Caveats on tomographic images

“…not subject to previous basaltic melt extraction) mantle compositions. A suite of global and regional studies have shown that, as a general rule, the effects of temperature and composition on buoyancy are comparable in the shallow continental mantle (Jordan, 1975;Forte and Perry, 2000;Kaban et al, 2003;Kelly et al, 2003;Artemieva, 2007;Brandmayr et al, 2011;Tumanian et al, 2012). In the deep mantle, composition and not temperature dominates buoyancy (Trampert and van der Hilst, 2005).…”

“…Only in a few cases have formal uncertainties in tomographic results been published (e.g. Panza et al, 2007;Brandmayr et al, 2010;Cor-chete andChourak, 2010, 2011;Raykova and Panza, 2010;Gonzales et al, 2011). If uncertainties were published routinely, many seismic anomalies interpreted geologically, widely used in undergraduate teaching, and relied upon to support geochemical and geodynamic models,…”

“…The best absolute models use all available data, including, for example, local and regional earthquakes and artificial sources, which introduce turning waves (e.g. Du and Panza, 1999;Panza et al, 2007;Brandmayr et al, 2011). These are superior to models based on adding calculated anomalies to starting models.…”

Transition from continental collision to tectonic escape? A geophysical perspective on lateral expansion of the northern Tibetan Plateau

“…This approach has been extensively applied to upper crustal problems; however, applications to the lower crust and upper mantle have been limited (e.g., Brandmayr et al 2011;Welford and Hall 2007;Welford et al 2010). Refined mesh design and sensible regularization procedures permit reasonable resolution of the Moho surface, whilst Figure 1 Tectonic map of the Tibetan Plateau (Yin and Harrison 2000).…”