A 3-D lithospheric model of the Caribbean-South American plate boundary

A 3-D structural model of the Caribbean-South American plate boundary was constructed by gravity modeling. The model was constrained by four wide-angle seismic refraction sections, Moho depth estimations from receiver functions, and additionally seismological hypocenters, surface geology, and geodynamic information. Density values were calculated from empirical velocity-density functions, and mineralogical-chemical composition considering specific P/T conditions. We tested different structural models for Western and Eastern Venezuela. In the final model, the fit of the measured and modeled gravity fields for a long Caribbean slab in Western Venezuela was better than the fit obtained for a short one. This interpretation is consistent with the constraining data. The slab is interpreted to extend further to the south beneath Northern Colombia and culminates in the area of the seismic cluster of the Bucaramanga nest. The modeling estimates a slab dip angle under Maracaibo and Mérida Andes of 15°, which increases to 32° below 100 km depth. The dip direction of approx. N150°E ± 5 increases lightly eastward. In Eastern Venezuela, considering its short wavelength, lineaments analyzed from gravity data (by curvature methods and Euler deconvolution) seem to be related to shallow structures and density contrast in the Serranía del Interior and not from a deep detached slab beneath the continental crust. It is deduced from modeling results that this slab configuration has a very small influence on the gravity field. The slab was modeled according to the subduction-transform propagation model with purely westward subduction and a slab break off along a vertical dip-slip tear through the lithosphere.     

CFD simulation of blasting dust for the design of physical barriers

A computational fluid dynamics (CFD) model has been developed to simulate the dispersion of dust generated in blasting located in limestone quarries. This is a complex phenomenon that has been studied through the use of several digital video recordings of blasts and dust concentration field measurements by ‘light scattering’ dust collectors. In addition, the subsequent simulation of the dispersion of the dust cloud by means of multiphase CFD has also been studied. CFD calculations were carried out using software Ansys CFX 10.0, through transitory models with Lagrangian particle models crossing an Eulerian air continuous phase. This paper presents results obtained by model simulations where physical barriers are set close to the blasting, with the aim of decreasing the dust cloud dispersal and the associated environmental impact.     

Furrows in the southern Scan Basin, Antarctica: interplay between tectonic and oceanographic influences

Multibeam echosounder data and TOPAS seismic reflection profiles collected during the AntPac 1997, Scan 2004, and Scan 2008 cruises aboard the RV Hespérides reveal a host of surficial geomorphological features as yet poorly investigated in the Scan Basin, south-central Scotia Sea. This area represents one of the deep gateways between the Weddell Sea and the Scotia Sea, since it enables the northward flow of a branch of the Weddell Sea Deep Water (WSDW). Analysis of the data identifies numerous elongated depressions interpreted as furrows in the southernmost sector of the basin. These furrows show two main trends, i.e., either N?CNNW parallel to, or NE oblique to regional bathymetric contours. These trends plausibly reflect a tectonic influence on the bottom-flow distribution, conditioned by a set of recent, conjugate strike-slip faults that developed on the seafloor under dominant NNE?CSSW compression and orthogonal extension. The furrows exhibit distinct geomorphological patterns at either side of the basin, which can be related to west?Ceast asymmetry in the WSDW flow direction. Consistent with existing knowledge of regional WSDW dynamics, northward WSDW overflows would be channeled along the western part of the basin at higher bottom-current velocities, thereby generating more erosional-type furrows that are straighter, more elongated, and have more abrupt sidewalls than their eastern counterparts. In contrast, weaker southward WSDW would flow along the eastern part of the basin, resulting in more depositional-type furrows that are more curved, less elongated, and have gentler sidewalls.     

The Imaging and Slitless Spectroscopy Instrument for Surveys (ISSIS): expected radiometric performance,operation modes and data handling

ISSIS is the instrument for imaging and slitless spectroscopy on-board WSO-UV. In this article, a detailed comparison between ISSIS expected radiometric performance and other ultraviolet instruments is shown. In addition, we present preliminary information on the performance verification tests and on the foreseen procedures for in-flight operation and data handling.     

Heat flow and depth to a possible internal ocean on Triton

The Raz Fossae, a pair of ≈15-km wide trough en echelon interpreted as grabens, can be used to propose an estimation of the depth to the brittle-ductile transition on Triton. This estimation may in turn give an idea of the thermal state of Triton's icy lithosphere when these features formed. Given the young age of its surface, the conclusions obtained could be roughly applicable to the present state of this satellite of Neptune. Considering water or ammonia dihydrate as possible components of the lithosphere and a feasible range of strain rates, it was estimated that surface heat flow is greater than that inferred from radiogenic heating, especially for a lithosphere dominated by water. Also, an internal ocean could lie at a depth of only ∼20 km beneath the surface. The presence over the surface of an insulating layer of ice of low thermal conductivity (e.g., nitrogen) or of regolith would only substantially alter these estimates if the effective surface temperature were considerably higher than the observed value of 38 K.     

Episodic flood inundations of the northern plains of Mars

Throughout the recorded history of Mars, liquid water has distinctly shaped its landscape, including the prominent circum-Chryse and the northwestern slope valleys outflow channel systems, and the extremely flat northern plains topography at the distal reaches of these outflow channel systems. Paleotopographic reconstructions of the Tharsis magmatic complex reveal the existence of an Europe-sized Noachian drainage basin and subsequent aquifer system in eastern Tharsis. This basin is proposed to have sourced outburst floodwaters that sculpted the outflow channels, and ponded to form various hypothesized oceans, seas, and lakes episodically through time. These floodwaters decreased in volume with time due to inadequate groundwater recharge of the Tharsis aquifer system. Martian topography, as observed from the Mars Orbiter Laser Altimeter, corresponds well to these ancient flood inundations, including the approximated shorelines that have been proposed for the northern plains. Stratigraphy, geomorphology, and topography record at least one great Noachian-Early Hesperian northern plains ocean, a Late Hesperian sea inset within the margin of the high water marks of the previous ocean, and a number of widely distributed minor lakes that may represent a reduced Late Hesperian sea, or ponded waters in the deepest reaches of the northern plains related to minor Tharsis- and Elysium-induced Amazonian flooding.     

A model of characteristic earthquakes and its implications for regional seismicity

Regional seismicity (i.e. that averaged over large enough areas over long enough periods of time) has a size–frequency relationship, the Gutenberg–Richter law, which differs from that found for some seismic faults, the Characteristic Earthquake relationship. But all seismicity comes in the end from active faults, so the question arises of how one seismicity pattern could emerge from the other. The recently introduced Minimalist Model of Vázquez‐Prada et al. of characteristic earthquakes provides a simple representation of the seismicity originating from a single fault. Here, we show that a Characteristic Earthquake relationship together with a fractal distribution of fault lengths can accurately describe the total seismicity produced in a region. The resulting earthquake catalogue accounts for the addition of both all the characteristic and all the non‐characteristic events triggered in the faults. The global accumulated size–frequency relationship strongly depends on the fault length fractal exponent and, for fractal exponents close to 2, correctly describes a Gutenberg–Richter distribution with a b exponent compatible with real seismicity.     

Cadomian volcanosedimentary complexes across the Ediacaran–Cambrian transition of the Eastern Pyrenees,southwestern Europe

International Journal of Earth Sciences - The volcanism hosted by the Ediacaran–Terreneuvian Canaveilles Group of the Eastern Pyrenees displays two distinct geochemical affinities: (1)...     

SO2 degassing from Turrialba Volcano linked to seismic signatures during the period 2008–2012

In 1996, after 150 years of relative calm, Turrialba Volcano was reawakening. A visible plume and serious damage to surrounding vegetation due to acid rain are the most obvious signals. As part of the Network for Observation of Volcanic and Atmospheric Change project, four gas-monitoring stations were initially installed on the west flank of the volcano with the purpose of measuring sulphur dioxide emissions during this period of increased activity using the scanning-differential optical absorption spectroscopy technique. We present here the results of semicontinuous gas flux measurements over a period of 5 years (from 2008 to 2012), providing a novel data set that documents a relatively rapid increase in SO₂ fluxes from around 350 t day^?1 to around 4,000 t day^?1 leading up to an eruptive period, followed by a gradual return to the former baseline values. Gas flux data were also compared with seismic data for selected periods of interest, providing insights into the link between degassing and seismicity. The most important result from this comparison is the identification of an inflexion point in the gas emissions followed by a clearly increasing trend in seismic activity, distinguishable 6 months prior to a phreatic eruptive event that occurred on 5 January 2010. This signal can be interpreted as a possible indicator of future eruptive events. Monitoring of SO₂ thus complements seismic monitoring as a forecasting tool for eruptive events. Such monitoring is critical considering the proximity of Turrialba to the Central Valley, an area inhabited by more than 50 % of Costa Rica’s population.