Moir\'e patterns on STM images of graphite from surface and subsurface rotated layer

We have observed with STM moir\'e patterns corresponding to the rotation of one graphene layer on HOPG surface. The moir\'e patterns were characterized by rotation angle and extension in the plane. Additionally, by identifying border domains and defects we can discriminate between moir\'e patterns due to rotation on the surface or subsurface layer. For a better understanding of moir\'e patterns formation we have studied by first principles an array of three graphene layers where the top or the middle layer appears rotated around the stacking axis. We compare the experimental and theoretical results and we show the strong influence of rotations both in surface and subsurface layers for moir\'e patterns formation in corresponding STM images.Comment: 5 pages, 6 figure

Numerical simulation of tsunami runup in northern Chile based on non-uniform k −2 slip distributions

Artículo de publicación ISIA large seismic gap lies along northern Chile and could potentially trigger a M (w) similar to 8.8-9.0 megathrust earthquake as pointed out in several studies. The April 1, 2014, Pisagua earthquake broke the middle segment of the megathrust. Some slip models suggest that it ruptured mainly from a depth of 30 to 55 km along dip and over 180 km in length, reaching a magnitude M (w) 8.1-8.2. The northern and southern segments are still unbroken; thus, there is still a large area that could generate a M (w) > 8.5 earthquake with a strong tsunami. To better understand the effects of source parameters on the impact of a tsunami in the near field, as a case study, we characterize earthquake size for a hypothetical and great seismic event, M (w) 9.0, in northern Chile. On the basis of physical earthquake source models, we generate stochastic k (-2) finite fault slips taking into account the non-planar geometry of the megathrust in northern Chile. We analyze a series of random slip models and compute vertical co-seismic static displacements by adding up the displacement field from all point sources distributed over a regular grid mesh on the fault. Under the assumption of passive generation, the tsunami numerical model computes the runup along the shore. The numerical results show a maximum peak-runup of similar to 35-40 m in the case of some heterogeneous slip models. Instead, the minimum runup along the coast, from the heterogeneous slip models tested, almost coincides with the runup computed from the uniform slip model. This latter assumption underestimates the runup by a factor of similar to 6 at some places along the coast, showing agreement with near-field runups calculated by other authors using similar methodologies, but applied in a different seismotectonic context. The statistical estimate of empirical cumulative distribution functions conducted on two subsets of slips, and their respective runups, shows that slip models with large amount of slip near the trench are more probable to produce higher runups than the other subset. The simple separation criterion was to choose slip models that concentrate at least 60 % of the total seismic moment in the upper middle part of the non-planar rupture fault.Conicyt (Comision Nacional de Ciencia y Tecnologia) under Grant Fondecyt 113063

Natural history of model organisms : The secret (group) life of Drosophila melanogaster larvae and why it matters to developmental ecology

ACKNOWLEDGMENTS ZP is funded by the Swedish Foundation for Strategic Research (SSF) within the Swedish National Graduate School in Neutron Scattering (SwedNess).Peer reviewedPublisher PD

Reconstructing paleoseismic deformation, 2: 1000 years of great earthquakes at Chucalén, south central Chile

In this paper we adopt a quantitative biostratigraphic approach to establish a 1000-year-long coastal record of megathrust earthquake and tsunami occurrence in south central Chile. Our investigations focus on a site in the centre of the rupture segment of the largest instrumentally recorded earthquake, the AD 1960 magnitude 9.5 Chile earthquake. At Chucalén coseismic subsidence in 1960 is recorded in the lithostratigraphy and biostratigraphy of coastal marshes, with peat overlain by minerogenic sediment and changes in the assemblages of diatoms (unicellular algae) indicating an abrupt increase in relative sea level. In addition to the 1960 earthquake, the stratigraphy at Chucalén records three earlier earthquakes, the historically documented earthquake of 1575 and two prehistoric earthquakes, radiocarbon dated to AD 1270–1450 and 1070–1220. Laterally extensive sand sheets containing marine or brackish diatom assemblages suggest tsunami deposition associated with at least two of the three pre-1960 earthquakes. The record presented here suggests a longer earthquake recurrence interval, averaging 270 years, than the historical recurrence interval, which averages 128 years. The lack of geologic evidence at Chucalén of two historically documented earthquakes, in 1737 and 1837, supports the previously suggested hypothesis of variability in historical earthquake characteristics. Our estimates of coseismic land-level change for the four earthquakes range from meter-scale subsidence to no subsidence or slight uplift, suggesting earthquakes completing each ∼270 year cycle may not share a common, characteristic slip distribution. The presence of buried soils at elevations below their modern equivalents implies net relative sea-level rise over the course of the Chucalén paleoseismic record, in contrast to relative sea-level fall over preceding millennia inferred from sites on the mainland. Sea-level rise may contribute to the preservation of evidence for multiple earthquakes during the last millennium, while net relative sea-level fall over the last 2000–5000 years may explain the lack of evidence for older earthquakes

Determination of seismogenic interplate contact zone and crustal seismicity around Antofagasta, Northern Chile using local data

International audienc

On a Conjecture of Goriely for the Speed of Fronts of the Reaction--Diffusion Equation

In a recent paper Goriely considers the one--dimensional scalar reaction--diffusion equation $u_t = u_{xx} + f(u)$ with a polynomial reaction term $f(u)$ and conjectures the existence of a relation between a global resonance of the hamiltonian system $u_{xx} + f(u) = 0$ and the asymptotic speed of propagation of fronts of the reaction diffusion equation. Based on this conjecture an explicit expression for the speed of the front is given. We give a counterexample to this conjecture and conclude that additional restrictions should be placed on the reaction terms for which it may hold.Comment: 9 pages Revtex plus 4 postcript figure