145 research outputs found
Regional trends and controlling factors of fatal landslides in Latin America and the Caribbean
A new data set of landslides that caused loss of life in Latin America and the
Caribbean in the 10-year period from 2004 and 2013 inclusive has been
compiled, providing new insight into the impact of landslides in this key
part of the world. This data set indicates that in the 10-year period a total
of 11 631 people lost their lives across the region in 611 landslides. The
geographical distribution of the landslides is highly heterogeneous, with
areas of high incidence in parts of the Caribbean (most notably Haiti),
Central America, Colombia, and southeast Brazil. There is significant interannual
variation in the number of landslides, with the El Niño/La Niña cycle
emerging as a key control. Our analysis suggests that on a continental scale
the mapped factors that best explain the observed distribution are
topography, annual precipitation and population density. On a national basis
we have compared the occurrence of fatality-inducing landslide occurrence
with the production of locally authored research articles, demonstrating that
there is a landslide research deficit in Latin America and the Caribbean.
Understanding better the mechanisms, distribution causes and triggers of
landslides in Latin America and the Caribbean must be an essential first step
towards managing the hazard
The archaeology of a landslide: Unravelling the Azores earthquake disaster of 1522 and its consequences
The multidisciplinary research described here shows how archaeologists can help reconstruct past seismic episodes and understand the subsequent relief operation, rehabilitation, and reconstruction processes. In October 1522, a major earthquake and landslide struck the then capital of the Azores, Vila Franca do Campo, 1500 km from the European mainland. Damage was extensive, destroying key monuments, affecting most of the inhabited area, and leaving few survivors among the early colonists. The results from twenty-six archaeological trenches, geological and geoarchaeological investigations, and documentary analysis are reviewed here. Distinctive archaeological deposits are identified and explained, using the high density of artefacts and the erosional contact between the landslide and the pre-1522 palaeosol to reconstruct the episode in detail
An acoustic emission landslide early warning system for communities in low-income and middle-income countries
This is an Open Access Article. It is published by Springer under the Creative Commons Attribution 4.0 Unported Licence (CC BY). Full details of this licence are available at: http://creativecommons.org/licenses/by/4.0/Early warning systems for slope instability are needed to alert users of accelerating slope deformation behaviour, enable evacuation of vulnerable people, and conduct timely repair and maintenance of critical infrastructure. Communities exposed to landslide risk in low- and middle-income countries seldom currently instrument and monitor slopes to provide a warning of instability because existing techniques are complex and prohibitively expensive. Research and field trials have demonstrated conclusively that acoustic emission (AE) monitoring can be an effective approach to detect accelerating slope movements and to subsequently communicate warnings to users. The objective of this
study was to develop and assess a simple, robust, low-cost AE monitoring system to warn of incipient landslides, which can be widely deployed and operated by communities globally to help protect vulnerable people. This paper describes a novel AE measurement sensor that has been designed and developed with the
cost constrained to a few hundred dollars (US). Results are presented from physical model experiments that demonstrate performance of the AE system in measuring accelerating deformation behaviour, with quantifiable relationships between AE and displacement rates. Exceedance of a pre-determined trigger level of AE can be used to communicate an alarm to users in order to alert them of a slope failure. Use of this EWS approach by communities worldwide would reduce the number of fatalities caused by landslides
Volume Characteristics of Landslides Triggered by the MW 7.8 2016 KaikĆura Earthquake, New Zealand, Derived From Digital Surface Difference Modeling
We use a mapped landslide inventory coupled with a 2âm resolution vertical difference model covering an area of 6,875Â km2 to accurately constrain landslide volumeâarea relationships. We use the difference model to calculate the source volumes for landslides triggered by the MW 7.8 KaikĆura, New Zealand, earthquake of 14 November 2016. Of the 29,519 mapped landslides in the inventory, 28,394 are within the analysis area, and of these, we have calculated the volume of 17,256 source areas that are â„90% free of debris. Of the 28,394 landslides, about 80% are classified as soil or rock avalanches and the remainder as mainly translational slides. Our results show that both the soil avalanches and the rock avalanches, ignoring their source geology, have area to volume powerâlaw scaling exponents (Îł) of 0.921 to 1.060 and 1.040 to 1.138, respectively. These are lower than the Îł values of 1.1â1.3 (for soil) and 1.3â1.6 (for rock) reported in the literature for undifferentiated landslide types. They are, however, similar to those Îł values estimated from other coseismic landslide inventories. In contrast, for 50 selected rotational, translational (planar slide surfaces), or compound slides, where much of the debris remains in the source area, we found Îł values range between 1.46 and 1.47, indicating that their slide surfaces were considerably deeper than those landslides classified as avalanches. This study, like previous studies on coseismic landslides, shows that soil and rock avalanches (disrupted landslides) are the dominant landslide type triggered by earthquakes and that they tend to be shallow.Key PointsWe use a 2âm resolution vertical difference model to estimate source volumes for 17,256 landslides with sources â„90% free of debris triggered by the MW7.8 2016 KaikĆura EarthquakeThe model was derived by subtracting a tectonically adjusted preâEQ surface model from a postâEQ model, covering an area of 6,875Â km2Landslide trigger mechanism, type/failure mode, and source material are critical for accurate estimation of landslide volumes from sourceâarea geometriesPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156166/2/jgrf21176.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156166/1/jgrf21176_am.pd
A novel Bayesian approach for decomposing the radio emission of quasars: I. Modelling the radio excess in red quasars
© 2024 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/Studies show that both radio jets from the active galactic nuclei (AGNs) and the star formation (SF) activity in quasar host galaxies contribute to the quasar radio emission; yet their relative contributions across the population remain unclear. Here, we present an improved parametric model that allows us to statistically separate the SF and AGN components in observed quasar radio flux density distributions, and investigate how their relative contributions evolve with AGN bolometric luminosity (\L\mathrm\bol\\) and redshift (z) using a fully Bayesian method. Based on the newest data from LOw-Frequency ARray Two-metre Sky Survey data release 2, our model gives robust fitting results out to \z\\, showing a quasar host galaxy SF rate (SFR) evolution that increases with bolometric luminosity and with redshift out to \z\\. This differs from the global cosmic SFR density, perhaps due to the importance of galaxy mergers. The prevalence of radio AGN emissions increases with quasar luminosity, but has little dependence on redshift. Furthermore, our new methodology and large sample size allow us to subdivide our data set to investigate the role of other parameters. Specifically, in this paper, we explore quasar colour and demonstrate that the radio excess in red quasars is due to an enhancement in AGN-related emission, since the host galaxy SF contribution to the total radio emission is independent of quasar colour. We also find evidence that this radio enhancement occurs mostly in quasars with weak or intermediate radio power.Peer reviewe
Dynamic liquefaction of shear zones in intact loess during simulated earthquake loading
The 2010-2011 Canterbury earthquake sequence in New Zealand exposed loess-mantled slopes in the area to very high levels of seismic excitation (locally measured as >2 g). Few loess slopes showed permanent local downslope deformation, and most of these showed only limited accumulated displacement. A series of innovative dynamic back pressured shear-box tests were undertaken on intact and remoulded loess samples collected from one of the recently active slopes replicating field conditions under different simplified horizontal seismic excitations. During each test, the strength reduction and excess pore water pressures generated were measured as the sample failed. Test results suggest that although dynamic liquefaction could have occurred, a key factor was likely to have been that the loess was largely unsaturated at the times of the large earthquake events. The failure of intact loess samples in the tests was complex and variable due to the highly variable geotechnical characteristics of the material. Some loess samples failed rapidly as a result of dynamic liquefaction as seismic excitation generated an increase in pore-water pressure, triggering rapid loss of strength and thus of shear resistance. Following initial failure, pore pressure dissipated with continued seismic excitation and the sample consolidated, resulting in partial shear-strength recovery. Once excess pore-water pressures had dissipated, deformation continued in a critical effective stress state with no further change in volume. Remoulded and weaker samples, however, did not liquefy, and instead immediately reduced in volume with an accompanying slower and more sustained increase in pore pressure as the sample consolidated. Thereafter excess pressures dissipated and deformation continued at a critical state. The complex behaviour explained why, despite exceptionally strong ground shaking, there was only limited displacement and lack of run-out: dynamic liquefaction was unlikely to occur in the freely draining slopes. Dynamic liquefaction however remained a plausible mechanism to explain loess failure in some of the low-angle toe slopes, where a permanent water table was present in the loess
The fundamental constants and their variation: observational status and theoretical motivations
This article describes the various experimental bounds on the variation of
the fundamental constants of nature. After a discussion on the role of
fundamental constants, of their definition and link with metrology, the various
constraints on the variation of the fine structure constant, the gravitational,
weak and strong interactions couplings and the electron to proton mass ratio
are reviewed. This review aims (1) to provide the basics of each measurement,
(2) to show as clearly as possible why it constrains a given constant and (3)
to point out the underlying hypotheses. Such an investigation is of importance
to compare the different results, particularly in view of understanding the
recent claims of the detections of a variation of the fine structure constant
and of the electron to proton mass ratio in quasar absorption spectra. The
theoretical models leading to the prediction of such variation are also
reviewed, including Kaluza-Klein theories, string theories and other
alternative theories and cosmological implications of these results are
discussed. The links with the tests of general relativity are emphasized.Comment: 56 pages, l7 figures, submitted to Rev. Mod. Phy
Possible variations of the fine structure constant and their metrological significance
We briefly review the recent experimental results on possible variations of
the fine structure constant on the cosmological time scale and its
position dependence. We outline the theoretical grounds for the assumption that
might be variable, mention some phenomenological models incorporating
a variable into the context of modern cosmology and discuss the
significance of possible variations for theoretical and practical
metrology.Comment: Latex, 17 pages, brief review. References updated, minor errors
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Rethinking cultural diversity in the UK film sector:practices in community filmmaking
© The Author(s) 2017. Academic, policy and industry debates have tended to focus on the mainstream film sector when discussing cultural diversity. One of the persistent challenges for the sector has been how to diversify cultural representation and participation. This article suggests that participatory modes of community filmmaking make an important contribution to cultural diversity. Drawing on an evidence base derived from qualitative research conducted in three English regions, the article shifts the spotlight away from the mainstream and onto the margins of the film sector in order to explore more âbottom-upâ approaches to cultural diversity. It examines how community filmmakers interpret and engage with questions of cultural diversity and how this connects to the participatory and business practices that they adopt. The findings highlight the significance of processes of practice in how mediated cultural diversity manifests itself and the value of community filmmaking in contributing to wider cultural diversity debates and practices.The authors thank the Arts and Humanities Research Council (UK) for funding the âCommunity Filmmaking and Cultural Diversity: Practice, Innovation and Policy projectâ (2013â2014)
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