Fast short-term lava flow hazard assessment with graph theory

2020 ◽  
Author(s):  
Veronica Centorrino ◽  
Giuseppe Bilotta ◽  
Annalisa Cappello ◽  
Gaetana Ganci ◽  
Claudia Corradino ◽  
...  
Keyword(s):  
Graph Theory ◽  
Lava Flow ◽  
Graph Representation ◽  
Computational Time ◽  
Hazard Map ◽  
Short Term ◽  
Flow Paths ◽  
Lava Flow Hazard ◽  
Mt Etna

<p>We explore the use of graph theory to assess short-term hazard of lava flow inundation, with Mt Etna as a case study. In the preparation stage, we convert into a graph the long-term hazard map produced using about 30,000 possible eruptive scenarios calculated by simulating lava flow paths with the physics-based MAGFLOW model. Cells in the original DEM-based representation are merged into graph vertices if reached by the same scenarios, and for each pair of vertices, a directed edge is defined, with an associated lava conductance (probability of lava flowing from one vertex to the other) computed from the number of scenarios that reach both the start and end vertex. In the application stage, the graph representation can be used to extract short-term lava flow hazard maps in case of unrest. When a potential vent opening area is identified e.g. from monitoring data, the corresponding vertices in the graph are activated, and the information about lava inundation probability is iteratively propagated to neighboring vertices through the edges, weighted according to the associated lava conductance. This allows quick identification of potentially inundated areas with little computational time. A comparison with the deterministic approach of subsetting and recomputing the weights in the long-term hazard map is also presented to illustrate benefits and downsides of the graph-based approach.</p>

scholarly journals Lava flow hazard map of Piton de la Fournaise volcano 

2021 ◽  
Author(s):  
Oryaëlle Chevrel ◽  
Massimiliano Favalli ◽  
Villeneuve Nicolas ◽  
Andrew Harris ◽  
Alessandro Fornaciai ◽  
...  
Keyword(s):  
Lava Flow ◽  
18Th Century ◽  
Hot Spot ◽  
Hazard Map ◽  
Hazard Maps ◽  
Flow Paths ◽  
Piton De La Fournaise ◽  
Lava Flow Hazard ◽  
Multi Temporal ◽  
Deep Sources

<p>Piton de la Fournaise, situated on La Réunion Island (France), is one of the most active hot spot basaltic shield volcanoes worldwide, experiencing at least two eruptions per year since the establishment of the observatory in 1979. Eruptions are typically fissure-fed and form extensive lava flow fields. About 95 % of some ~250 historical events (since the first confidently dated eruption in 1708) have occurred inside an uninhabited horse-shoe shaped caldera (hereafter referred to as the Enclos) which is open to the ocean on its eastern side. Rarely (12 times since the 18th century), fissures have opened outside of the Enclos where housing units, population centers and infrastructure are at risk. In such a situation, lava flow hazard maps are a useful way of visualizing lava flow inundation probabilities over large areas. Here, we present a lava flow hazard map for Piton de la Fournaise volcano based on: i) vent distribution, ii) statistics of lava flow lengths, iii) lava flow recurrence times, and iv) simulations of lava flow paths across multi-temporal (i.e., regularly updated) topography using the DOWNFLOW stochastic numerical model. A map of the entire volcano highlights that the most probable (up to 12 %) location for future lava flow inundation is within the Enclos, where about 100,000 visitors are present each year. Hazard distribution changes throughout the analysis period due to the high frequency of eruptions that constantly modifies the vent opening distribution as well as the topography and the lava flow dimensional characteristics. Outside of the Enclos, probabilities reach 0.5 % along the well-defined rift zones and, although hazard occurrence in inhabited areas is deemed to be very low (<0.1 %), it may be underestimated here, as our study is only based on post-18th century records and neglects cycles of activity at the volcano. Specific hazard maps considering different event scenarios (i.e., events fed by different combinations of temporally evolving superficial and deep sources) are required to better assess affected areas in the future – especially by atypical, but potentially extremely hazardous, large volume eruptions. At such an active site, our method supports the need for regular updates of DEMs and associated lava flow hazard maps if we are to be effective in mitigating the associated risks.</p>

scholarly journals Lava flow hazard map of Piton de la Fournaise volcano

2021 ◽  
Vol 21 (8) ◽  
pp. 2355-2377
Author(s):  
Magdalena Oryaëlle Chevrel ◽  
Massimiliano Favalli ◽  
Nicolas Villeneuve ◽  
Andrew J. L. Harris ◽  
Alessandro Fornaciai ◽  
...  
Keyword(s):  
Lava Flow ◽  
Hazard Assessment ◽  
Land Use Planning ◽  
18Th Century ◽  
Hot Spot ◽  
Hazard Map ◽  
Hazard Maps ◽  
Piton De La Fournaise ◽  
Lava Flow Hazard

Abstract. Piton de la Fournaise, situated on La Réunion island (France), is one of the most active hot spot basaltic shield volcanoes worldwide, experiencing at least two eruptions per year since the establishment of the volcanological observatory in 1979. Eruptions are typically fissure-fed and form extensive lava flow fields. About 95 % of some ∼ 250 historical events (since the first confidently dated eruption in 1708) have occurred inside an uninhabited horseshoe-shaped caldera (hereafter referred to as the Enclos), which is open to the ocean on its eastern side. Rarely (12 times since the 18th century), fissures have opened outside of the Enclos, where housing units, population centers, and infrastructure are at risk. In such a situation, lava flow hazard maps are a useful way of visualizing lava flow inundation probabilities over large areas. Here, we present the up-to-date lava flow hazard map for Piton de la Fournaise based on (i) vent distribution, (ii) lava flow recurrence times, (iii) statistics of lava flow lengths, and (iv) simulations of lava flow paths using the DOWNFLOW stochastic numerical model. The map of the entire volcano highlights the spatial distribution probability of future lava flow invasion for the medium to long term (years to decades). It shows that the most probable location for future lava flow is within the Enclos (where there are areas with up to 12 % probability), a location visited by more than 100 000 visitors every year. Outside of the Enclos, probabilities reach 0.5 % along the active rift zones. Although lava flow hazard occurrence in inhabited areas is deemed to be very low (< 0.1 %), it may be underestimated as our study is only based on post-18th century records and neglects older events. We also provide a series of lava flow hazard maps inside the Enclos, computed on a multi-temporal (i.e., regularly updated) topography. Although hazard distribution remains broadly the same over time, some changes are noticed throughout the analyzed periods due to improved digital elevation model (DEM) resolution, the high frequency of eruptions that constantly modifies the topography, and the lava flow dimensional characteristics and paths. The lava flow hazard map for Piton de la Fournaise presented here is reliable and trustworthy for long-term hazard assessment and land use planning and management. Specific hazard maps for short-term hazard assessment (e.g., for responding to volcanic crises) or considering the cycles of activity at the volcano and different event scenarios (i.e., events fed by different combinations of temporally evolving superficial and deep sources) are required for further assessment of affected areas in the future – especially by atypical but potentially extremely hazardous large-volume eruptions. At such an active site, our method supports the need for regular updates of DEMs and associated lava flow hazard maps if we are to be effective in keeping up to date with mitigation of the associated risks.

scholarly journals Lava flow hazard map of Piton de la Fournaise volcano

2020 ◽  
Author(s):  
Magdalena Oryaëlle Chevrel ◽  
Massimiliano Favalli ◽  
Nicolas Villeneuve ◽  
Andrew J. L. Harris ◽  
Alessandro Fornaciai ◽  
...  
Keyword(s):  
Lava Flow ◽  
18Th Century ◽  
Hot Spot ◽  
Hazard Map ◽  
Flow Paths ◽  
Piton De La Fournaise ◽  
Lava Flow Hazard ◽  
Multi Temporal ◽  
La Réunion Island ◽  
Hazard Distribution

Abstract. Piton de la Fournaise, situated on La Réunion Island (France), is one of the most active hot spot basaltic shield volcanoes worldwide, experiencing at least two eruptions per year since the establishment of the observatory in 1979. Eruptions are typically fissure-fed and form extensive lava flow fields. About 95 % of some ~250 historical events (since the first confidently dated eruption in 1708) have occurred inside an uninhabited horse-shoe shaped caldera (hereafter referred to as the Enclos) which is open to the ocean on its eastern side. Rarely (12 times since the 18th century), fissures have opened outside of the Enclos where housing units, population centers and infrastructure are at risk. In such a situation, lava flow hazard maps are a useful way of visualizing lava flow inundation probabilities over large areas. Here, we present a lava flow hazard map for Piton de la Fournaise volcano based on: i) vent distribution, ii) statistics of lava flow lengths, iii) lava flow recurrence times, and iv) simulations of lava flow paths across multi-temporal (i.e., regularly updated) topography using the DOWNFLOW stochastic numerical model. A map of the entire volcano highlights that the most probable (up to 12 %) location for future lava flow inundation is within the Enclos, where about 100,000 visitors are present each year. Hazard distribution changes throughout the analysis period due to the high frequency of eruptions that constantly modifies the vent opening distribution as well as the topography and the lava flow dimensional characteristics. Outside of the Enclos, probabilities reach 0.5 % along the well-defined rift zones and, although hazard occurrence in inhabited areas is deemed to be very low (

scholarly journals Retrospective validation of a lava-flow hazard map for Mount Etna volcano

2011 ◽  
Vol 54 (5) ◽  
Author(s):  
Annalisa Cappello ◽  
Annamaria Vicari ◽  
Ciro Del Negro
Keyword(s):  
Lava Flow ◽  
Mount Etna ◽  
Hazard Map ◽  
Etna Volcano ◽  
Lava Flow Hazard

Lava-flow hazard on the SE flank of Mt. Etna (Southern Italy)

2008 ◽  
Vol 177 (4) ◽  
pp. 778-796 ◽  
Author(s):  
G.M. Crisci ◽  
G. Iovine ◽  
S. Di Gregorio ◽  
V. Lupiano
Keyword(s):  
Lava Flow ◽  
Southern Italy ◽  
Lava Flow Hazard ◽  
Mt Etna

Supplementary material to "Lava flow hazard map of Piton de la Fournaise volcano"

2020 ◽  
Author(s):  
Magdalena Oryaëlle Chevrel ◽  
Massimiliano Favalli ◽  
Nicolas Villeneuve ◽  
Andrew J. L. Harris ◽  
Alessandro Fornaciai ◽  
...  
Keyword(s):  
Lava Flow ◽  
Hazard Map ◽  
Piton De La Fournaise ◽  
Lava Flow Hazard ◽  
Supplementary Material

Lava flow risk assessment on Mount Etna through hazard and exposure modelling

2020 ◽  
Author(s):  
Annalisa Cappello ◽  
Giuseppe Bilotta ◽  
Claudia Corradino ◽  
Gaetana Ganci ◽  
Alexis Hérault ◽  
...  
Keyword(s):  
Land Use ◽  
Lava Flow ◽  
Mount Etna ◽  
Service Networks ◽  
Analytic Hierarchy ◽  
Flow Paths ◽  
Thematic Layers ◽  
Exposed Population ◽  
Mt Etna ◽  
High Resolution Satellite Imagery

&lt;p&gt;Lava flows represent the greatest threat to exposed population and infrastructure on Mt Etna volcano (Italy). The increasing exposure of a larger population, which has almost tripled in the area around Mt Etna during the last 150 years, has resulted from poor assessment of the volcanic hazard, allowing inappropriate land use in vulnerable areas. We present a new methodology to quantify the lava flow risk on Etna&amp;#8217;s flanks using a GIS-based approach that integrates the hazard with the exposure of elements at stake. The hazard, showing the long-term probability related to lava flow inundation, is obtained by combining three different kinds of information: the spatiotemporal probability of the future opening of new flank eruptive vents, the event probability associated with classes of expected eruptions, and the overlapping of lava flow paths simulated by the MAGFLOW model. Data including all exposed elements have been gathered from institutional web portals and high-resolution satellite imagery, and organized in four thematic layers: population, buildings, service networks, and land use. The total exposure is given by a weighted linear combination of the four thematic layers, where weights are calculated using the Analytic Hierarchy Process (AHP). The resulting risk map shows the likely damage caused by a lava flow eruption, allowing rapid visualization of the areas subject to the greatest losses if a flank eruption were to occur on Etna.&lt;/p&gt;

Conceptual short-term memory (CSTM) supports core claims of Christiansen and Chater

2016 ◽  
Vol 39 ◽  
Author(s):  
Mary C. Potter
Keyword(s):  
Working Memory ◽  
Rapid Serial Visual Presentation ◽  
Language Comprehension ◽  
Short Term Memory ◽  
Visual Presentation ◽  
Long Term Memory ◽  
Short Term ◽  
Term Memory ◽  
Use Of Knowledge

AbstractRapid serial visual presentation (RSVP) of words or pictured scenes provides evidence for a large-capacity conceptual short-term memory (CSTM) that momentarily provides rich associated material from long-term memory, permitting rapid chunking (Potter 1993; 2009; 2012). In perception of scenes as well as language comprehension, we make use of knowledge that briefly exceeds the supposed limits of working memory.

Ultrastructural investigations of MDL 19,660-induced effects on the canine platelet and megakaryocyte

1990 ◽  
Vol 48 (3) ◽  
pp. 374-375
Author(s):  
D.E. Loudy ◽  
J. Sprinkle-Cavallo ◽  
J.T. Yarrington ◽  
F.Y. Thompson ◽  
J.P. Gibson
Keyword(s):  
Antidepressant Drug ◽  
Beagle Dogs ◽  
Long Term Effects ◽  
Short Term ◽  
Platelet Counts ◽  
Toxicological Studies ◽  
Induced Aggregation ◽  
Internal Architecture

Previous short term toxicological studies of one to two weeks duration have demonstrated that MDL 19,660 (5-(4-chlorophenyl)-2,4-dihydro-2,4-dimethyl-3Hl, 2,4-triazole-3-thione), an antidepressant drug, causes a dose-related thrombocytopenia in dogs. Platelet counts started to decline after two days of dosing with 30 mg/kg/day and continued to decrease to their lowest levels by 5-7 days. The loss in platelets was primarily of the small discoid subpopulation. In vitro studies have also indicated that MDL 19,660: does not spontaneously aggregate canine platelets and has moderate antiaggregating properties by inhibiting ADP-induced aggregation. The objectives of the present investigation of MDL 19,660 were to evaluate ultrastructurally long term effects on platelet internal architecture and changes in subpopulations of platelets and megakaryocytes.Nine male and nine female beagle dogs were divided equally into three groups and were administered orally 0, 15, or 30 mg/kg/day of MDL 19,660 for three months. Compared to a control platelet range of 353,000- 452,000/μl, a doserelated thrombocytopenia reached a maximum severity of an average of 135,000/μl for the 15 mg/kg/day dogs after two weeks and 81,000/μl for the 30 mg/kg/day dogs after one week.

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