1,024 research outputs found

    The fast response of volcano-seismic activity to intense precipitation: Triggering of primary volcanic activity by rainfall at Soufrière Hills Volcano, Montserrat

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    One-minute resolution time series of rainfall and seismic data from the Soufriere Hills Volcano, Montserrat are analysed to explore the mechanism of external forcing of volcanic eruptions by rainfall over three years of activity. The real-time seismic amplitude (RSAM) shows a narrow, statistically significant, peak within 30 min after the start of intense rainfall events, and a much broader peak with a lag of 6?40 h. The classified seismic events indicate that the volcanic response to rainfall begins at the surface and gradually penetrates deeper into the dome, as there is an increase in the pseudo-magnitude of: surface rockfall events (including pyroclastic flows) with lags from the first 30 min to 40 h, long-period rockfalls (from shallow degassing) at lags of 4 and 14 h, and long-period and hybrid events (source depth approximately 1 km) with lags at 14 and 24 h after the start of rainfall events. There was no rainfall-related change in deeper, volcano-tectonic activity. There was no change in the frequency of any type of classified event, indicating that the rainfall acts to modulate existing, internal processes, rather than generating new events itself. These robust results are due to many (229) different rainfall events, and not just to a few, large magnitude cases. The rainfalltriggered volcanic activity examined here is consistent with a model of fast, shallow interactions with rainfall at the dome surface, after which, a deeper dome collapse follows

    Capital and Punishment: Resource Scarcity Increases Endorsement of the Death Penalty

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    Faced with punishing severe offenders, why do some prefer imprisonment whereas others impose death? Previous research exploring death penalty attitudes has primarily focused on individual and cultural factors. Adopting a functional perspective, we propose that environmental features may also shape our punishment strategies. Individuals are attuned to the availability of resources within their environments. Due to heightened concerns with the costliness of repeated offending, we hypothesize that individuals tend toward elimination-focused punishments during times of perceived scarcity. Using global and United States data sets (studies 1 and 2), we find that indicators of resource scarcity predict the presence of capital punishment. In two experiments (studies 3 and 4), we find that activating concerns about scarcity causes people to increase their endorsement for capital punishment, and this effect is statistically mediated by a reduced willingness to risk repeated offenses. Perceived resource scarcity shapes our punishment preferences, with important policy implications

    Real-time assessment of potential seismic migration within a monitoring network using Red-flag SARA

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    Magma opening new fluid pathways through the crust can generate migrating seismic sources following the trail of the magma. By using Seismic Amplitude Ratio Analysis (SARA), it is possible to detect this seismic migration simply from the amplitudes of continuous data recorded at different stations in a network, without having to do any picking of seismic phases. In this study, we present a modified method – Red-flag SARA, which adapts SARA for real-time monitoring. Red-flag SARA provides a quantitative tool to analyse amplitude ratios between stations in a network and detect temporal changes in these ratios. Since such changes imply seismic source location variations, Red-flag SARA is a handy tool during seismic crises to quickly answer the question of whether seismic activity, and therefore magma, is migrating or not. We tested Red-flag SARA on synthetic data and validated it using real data from two volcanoes – Piton de la Fournaise, Reunion Island, and Gede, Indonesia, for three scenarios: 1) magma migration ending as intrusion, 2) migration leading to eruption and 3) a burst of seismicity with no magma migration

    Explosive Dome Eruptions Modulated by Periodic Gas-Driven Inflation

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    Volcan Santiaguito (Guatemala) “breathes” with extraordinary regularity as the edifice\u27s conduit system accumulates free gas, which periodically vents to the atmosphere. Periodic pressurization controls explosion timing, which nearly always occurs at peak inflation, as detected with tiltmeters. Tilt cycles in January 2012 reveal regular 26 ± 6 min inflation/deflation cycles corresponding to at least ~101 kg/s of gas fluxing the system. Very long period (VLP) earthquakes presage explosions and occur during cycles when inflation rates are most rapid. VLPs locate ~300 m below the vent and indicate mobilization of volatiles, which ascend at ~50 m/s. Rapid gas ascent feeds pyroclast-laden eruptions lasting several minutes and rising to ~1 km. VLPs are not observed during less rapid inflation episodes; instead, gas vents passively through the conduit producing no infrasound and no explosion. These observations intimate that steady gas exsolution and accumulation in shallow reservoirs may drive inflation cycles at open-vent silicic volcanoes

    CO Total and preferential oxidation over stable Au/TiO2 catalysts derived from preformed au nanoparticles

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    CO preferential oxidation (PROX) is an effective method to clean reformate H2 streams to feed low-temperature fuel cells. In this work, the PROX and CO oxidation reactions were studied on preformed Au nanoparticles (NPs) supported on TiO2 anatase. Preformed Au NPs were obtained from gold cores stabilized by dodecanethiols or trimethylsilane-dendrons. A well-controlled size of ca. 2.6 nm and narrow size distributions were achieved by this procedure. The catalysts were characterized by high-resolution transmission electron microscopy and ex situ and in situ X-ray photoelectron spectroscopy (XPS). The XPS results showed that the preformed Au NPs exhibited high thermal stability. The different ligand-derived Au catalysts, as well as a conventional gold catalyst for comparison purposes, were loaded onto cordierite supports with 400 cells per square inch. The activity and selectivity of the samples were evaluated for various operation conditions. The catalyst prepared using dodecanethiol-capped Au NPs showed the best performance. In fact, CO conversions of up to 70% at 40% CO2 selectivity and 90% O2 conversion were observed operating at 363 K in H2-rich atmospheres. The performance of the best catalysts was subsequently tested on stainless steel microreactors. A 500-hour stability test was carried out under a real post-reformate stream, including 18 vol.% CO2 and 29 vol.% H2O. A mean CO conversion of ca. 24% was measured for the whole test operating at 453 K and a gas hourly space velocity (GHSV) of 1.3 × 104 h−1. These results reveal our dodecanethiol-and carbosilane-derived Au catalysts as extremely promising candidates to conduct a PROX reaction while avoiding deactivation, which is one of the major drawbacks of Au/TiO2 catalysts.Fil: Divins, Núria J.. Universidad Politécnica de Catalunya; EspañaFil: Lopez, Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Angurell, Inmaculada. Universidad de Barcelona. Facultad de Química; EspañaFil: Neuberg, Stefan. Fraunhofer Institute of Microengineering and Microsystems; AlemaniaFil: Zapf, Ralf. Fraunhofer Institute of Microengineering and Microsystems; AlemaniaFil: Kolb, Gunther. Fraunhofer Institute of Microengineering and Microsystems; AlemaniaFil: Llorca Piqué, Jordi. Universidad Politécnica de Catalunya; Españ
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