[1] We analyze the mechanical properties needed to account for the large shallow slip during the 2011 Tohoku-Oki earthquake and the activation of landward normal faulting within the forearc. We show that the morphology and internal structure of the forearc follows closely the prediction of the critical Coulomb wedge in horizontal compression, implying a high internal pore pressure ratio ( = 0.7 + 0.14/ -0.48) and a low effective basal friction ( eff b = 0.14 + 0.18/ -0.04). We then show that the activation of the normal fault requires a lower effective basal friction beneath the outer wedge than beneath the inner wedge ( outer Ä 0.015), possibly due to transient dynamic weakening associated to the seismic rupture. Forearc normal faults could be considered as evidence for very efficient dynamic weakening along the megathrust and typify megathrust with high tsunamigenic potential.Citation: Cubas, N., J. P. Avouac, Y. M. Leroy, and A. Pons (2013), Low friction along the high slip patch of the 2011 Mw 9.0 Tohoku-Oki earthquake required from the wedge structure and extensional splay faults, Geophys. Res. Lett., 40,[4231][4232][4233][4234][4235][4236][4237]

A critical complication in handling nanoparticles is the formation of large aggregates when particles are dried e.g. when they need to be transferred from one liquid to another. The particles in these aggregates need to disperse into the destined liquid medium, which has been proven difficult due to the relatively large interfacial interaction forces between nanoparticles. We present a simple method to capture, move and release nanoparticles without the formation of large aggregates. To do so, we employ the co-non-solvency effect of poly(N-isopropylacrylamide) (PNIPAM) brushes in water-ethanol mixtures. In pure water or ethanol, the densely end-anchored macromolecules in the PNIPAM brush stretch and absorb the solvent. We show that under these conditions, the adherence between the PNIPAM brush and a silicon oxide, gold, polystyrene or poly(methyl methacrylate) colloid attached to an atomic force microscopy cantilever is low. In contrast, when the PNIPAM brushes are in a collapsed state in a 30-70 vol% ethanol-water mixture, the adhesion between the brush and the different counter surfaces is high. For potential application, we demonstrate that this difference in adhesion can be utilized to pick up, move and release 900 silicon oxide nanoparticles of diameter 80 nm using only 10 × 10 μm PNIPAM brush.

We propose a dynamical mechanism leading to the fluidization by external mechanical fluctuations of soft-glassy amorphous material driven below the yield-stress. The model is based on the combination of memory effect and non-linearity, leading to an accumulation of tiny effects over a long-term. We test this scenario on a granular packing driven mechanically below the Coulomb threshold. We bring evidences for an effective viscous response directly related to small stress modulations in agreement with the theoretical prediction of a generic secular drift. We finally propose to extend this result more generally, to a large class of glassy systems.PACS numbers: 81.40. Lm, 83.80.Fg Numerous amorphous materials such as concentrated suspensions, colloidal glasses, foams or granular materials share common global features in their mechanical response to shear [1,2]. They are characterized by a yield stress below which the material appears as a solid [3,4]. As this behaviour is shared by so many different materials, several conceptual and theoretical frameworks emerged recently [5][6][7][8][9][10] to provide a quantitative basis for the phenomenology of soft glassy rheology (SGR) above and beyond the yield stress. Even though many parallel approaches exist, sometimes at different level of description, they all share either explicitly or implicitly, the underlying idea that mesoscopic collective processes triggered by thermal or mechanical activation, contribute to the material fluidity. The direct visualization of local plastic events and the associated complex avalanching dynamics is supported by many experimental [11][12][13][14] or numerical [15][16][17] studies. In the "solid phase" corresponding to a strong dynamical arrest, soft-glassy systems display ageing properties manifesting in a slow creep relaxation process [18][19][20][21]. Ageing properties stem from a remaining thermal activation providing the possibility to cross enthalpic or entropic barriers and progressively set the system into deeper local minima where mechanical solidity is reinforced. The existence of external mechanical noise was also proposed as a substitute for thermal activation. In this sense, the behaviour of these amorphous soft glassy solids is very close phenomenologically to molecular glass-formers obtained by thermal quenching [22]. Yet, the fact that such mechanical noise truly acts as an effective temperature is presently debated [23] and indeed, deep differences in the way thermal noise and mechanical fluctuations act in amorphous systems has been recently pointed out [24].

Suspensions of cornstarch in water exhibit strong dynamic shear-thickening. We show that partly replacing water by ethanol strongly alters the suspension rheology. We perform steady and nonsteady rheology measurements combined with atomic force microscopy to investigate the role of fluid chemistry on the macroscopic rheology of the suspensions and its link with the interactions between cornstarch grains. Upon increasing the ethanol content, the suspension goes through a yield-stress fluid state and ultimately becomes a shear-thinning fluid. On the cornstarch grain scale, atomic force microscopy measurements reveal the presence of polymers on the cornstarch surface, which exhibit a cosolvency effect. At intermediate ethanol content, a maximum of polymer solubility induces high microscopic adhesion which we relate to the macroscopic yield stress.Suspensions are mixtures of undissolved particles in a liquid. They are literally found all around us: mud, paints, pastes and blood [1]. The viscosity of a dense suspension can vary by orders of magnitude in a small shear rate interval [2]. Subjected to an increasing shear rate, dense suspensions first tend to become less viscous (shear-thinning) and then more viscous (shearthickening). The viscosity of some suspensions, especially non-Brownian ones, may increase so much that they effectively become solid [3]. Although standard rheology measurements provide a great tool to study this phenomenon [e.g. 4, 5], they are mainly limited to steadystate conditions.Many studies point out that dense suspensions exhibit remarkable dynamic phenomena emerging under non-steady-shear conditions: stable holes in thin vibrated layers [6], non-monotonic settling [7], dynamic compaction front [8] or fracturing [3]. Oscillatory rheology helps to describe some of these dynamic behaviours [9], but remains limited to constant volume conditions. Dynamic shear-thickening has been widely investigated [10], but its physical origin remains an active debate. Although several parameters seem to contribute to it (e.g. particles size [11], shape [12] or roughness [13]), it has become increasingly clear that frictional and non-contact interactions between particles play a key role [14,15]. Such interactions are easily modified in numerical simulations, but present a real challenge in experiments. Consequently, only few experimental studies addressthe role of particle-particle interactions in dense suspensions rheology [e.g. 5, 16] however lacking systematic variation of these interactions. Moreover, direct measurements of these interactions in relation to the rheology are also lacking so far.Here, we directly probe the microscopic interactions between individual particles and explore their link with * adeline.pons@normalesup.org the macroscopic rheology for dense cornstarch (CS) suspensions. The archetypical suspension of CS grains in water exhibits a strong dynamic shear-thickening [3,[6][7][8]. Interestingly, Taylor [17] shows that replacing water by polypropylene glycol in CS suspensions completely su...