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131.
Rapid decompression experiments on natural volcanic rocks mimick explosive eruptions. Fragment size distributions (FSD) of such experimentally generated pyroclasts are investigated using fractal geometry. The fractal dimension of fragmentation, D, of FSD is measured for samples from Unzen (Japan) and Popocatépetl (Mexico) volcanoes.Results show that: (i) FSD are fractal and can be quantified by measuring D values; (ii) D increases linearly with potential energy for fragmentation (PEF) and, thus, with increasing applied pressure; (iii) the rate of increase of D with PEF depends on open porosity: the higher the open porosity, the lower the increase of D with PEF; (iv) at comparable open porosity, samples display a similar behavior for any rock composition.The method proposed here has the potential to become a standard routine to estimate eruptive energy of past and recent eruptions using values of D and open porosity, providing an important step towards volcanic hazard assessment. 相似文献
132.
Victoria González-Carman Natalia Machain Diego Albareda Hermes Mianzan Claudio Campagna 《Marine Policy》2012
This paper explores conservation policy pertinent to three species of marine turtles affected by fisheries, while crossing jurisdictions in their seasonal migrations through the SW Atlantic, particularly the Argentine waters. This case study reviews local legal and institutional frameworks for Argentina and concludes that tools are in place to monitor and mitigate the negative impact of bycatch on the populations. Argentina is signatory of the most relevant international treaties aimed at protecting transboundary species (e.g. Inter-American Convention for the Protection and Conservation of Sea Turtles, Convention on the Conservation of Migratory Species of Wild Animals). Legislation also exists at the federal and provincial levels. Yet, accidental captures continue to occur due to weaknesses in enforcement and the low priority that conservation has in fisheries management decisions. Some urgent practical actions supported by policy are suggested: (a) placement of on-board observers in coastal fishing fleets, (b) application of existing mitigation measures to reduce bycatch, (c) design of a national plan of action for marine turtles in Argentina, and (d) development of a regional plan between Argentina, Brazil and Uruguay. Stakeholder involvement, especially the fishing sector but also the civil society, would be important to energize practical and effective conservation decisions. The example of Argentina is typical for the region and may apply to other countries as well. The conservation community requires investing more in the application of policy, concomitant with perfecting legal tools. 相似文献
133.
The earliest known record of an aurora sighting in North America was made by Jesuit missionaries in New Brunswick, Canada, in the year 1611. Here, we wish to report an earlier record made in 1602 by the Notary Public of the Spanish Manila Galleon “San Antonio de Padua” while sailing near the coast of California. We also include a brief account of the circumstances and peculiar concurrence of events leading to the 1602 sighting. 相似文献
134.
A comparison of seismic risk maps for Italy 总被引:5,自引:3,他引:2
Helen Crowley Miriam Colombi Barbara Borzi Marta Faravelli Mauro Onida Manuel Lopez Diego Polli Fabrizio Meroni Rui Pinho 《Bulletin of Earthquake Engineering》2009,7(1):149-180
National seismic risk maps are an important risk mitigation tool as they can be used for the prioritization of regions within
a country where retrofitting of the building stock or other risk mitigation measures should take place. The production of
a seismic risk map involves the convolution of seismic hazard data, vulnerability predictions for the building stock and exposure
data. The seismic risk maps produced in Italy over the past 10 years are compared in this paper with recent proposals for
seismic risk maps based on state-of-the-art seismic hazard data and mechanics-based vulnerability assessment procedures. The
aim of the paper is to open the discussion for the way in which future seismic risk maps could be produced, making use of
the most up-to-date information in the fields of seismic hazard evaluation and vulnerability assessment. 相似文献
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139.
Christian Creixell Miguel Ángel Parada Diego Morata Pierrick Roperch César Arriagada 《International Journal of Earth Sciences》2009,98(1):177-201
Five mafic dike swarms between 30° and 33°45′S were studied for their geochemical signature and kinematics of magma flow directions
by means of AMS data. In the Coastal Range of central Chile (33°−33°45′S), Middle Jurassic dike swarms (Concón and Cartagena
dike swarms, CMDS and CrMDS, respectively) and an Early Cretaceous dike swarm (El Tabo Dike Swarm, ETDS) display the presence
of dikes of geochemically enriched (high-Ti) and depleted (low-Ti) basaltic composition. These dikes show geochemical patterns
that are different from the composition of mafic enclaves of the Middle Jurassic Papudo-Quintero Complex, and this suggests
that the dikes were injected from reservoirs not related to the plutonic complex. The mantle source appears to be a depleted
mantle for Jurassic dikes and a heterogeneous-enriched lithospheric mantle for Cretaceous dikes. In the ETDS, vertical and
gently plunging magma flow vectors were estimated for enriched and depleted dikes, respectively, which suggest, together with
variations in dike thickness, that reservoirs were located at different depths for each dike family. In the Elqui Dike Swarm
(EDS) and Limarí Mafic Dike Swarm (LMDS), geochemical patterns are similar to those of the mafic enclaves of the Middle Jurassic
plutons. In the LMDS, east to west magma flow vectors are coherent with injection from neighbouring pluton located to the
east. In the EDS, some dikes show geochemical and magma flow patterns supporting the same hypothesis. Accordingly, dikes do
not necessarily come from deep reservoir; they may propagate in the upper crust from coeval shallow pluton chamber.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
140.
M. Victoria Alonso Carlos Valotto Diego G. Lambas Hernán Muriel 《Monthly notices of the Royal Astronomical Society》1999,308(3):618-622
We present 83 new galaxy radial velocities in the field of 18 APM clusters with redshifts between 0.06 and 0.13. The clusters have Abell identifications and the galaxies were selected within 0.75 h −1 Mpc in projection from their centres. We derive new cluster velocity dispersions for 13 clusters using our data and published radial velocities.
We analyse correlations between cluster velocity dispersions and cluster richness counts as defined in Abell and APM catalogues. The correlations show a statistically significant trend although with a large scatter, suggesting that richness is a poor estimator of cluster mass irrespectively of cluster selection criteria and richness definition. We find systematically lower velocity dispersions in the sample of Abell clusters that do not fulfil APM cluster selection criteria, suggesting artificially higher Abell richness counts owing to contamination by projection effects in this subsample. 相似文献
We analyse correlations between cluster velocity dispersions and cluster richness counts as defined in Abell and APM catalogues. The correlations show a statistically significant trend although with a large scatter, suggesting that richness is a poor estimator of cluster mass irrespectively of cluster selection criteria and richness definition. We find systematically lower velocity dispersions in the sample of Abell clusters that do not fulfil APM cluster selection criteria, suggesting artificially higher Abell richness counts owing to contamination by projection effects in this subsample. 相似文献