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Kurama Okubo - One of the best experts on this subject based on the ideXlab platform.
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dynamics radiation and overall Energy Budget of earthquake rupture with coseismic off fault damage
Journal of Geophysical Research, 2019Co-Authors: Kurama Okubo, Harsha S Bhat, Esteban Rougier, Samson Marty, Alexandre Schubnel, Earl E Knight, Zhou Lei, Yann KlingerAbstract:Earthquake ruptures dynamically activate coseismic off-fault damage around fault cores. Systematic field observation efforts have shown the distribution of off-fault damage around main faults, while numerical modeling using elastic-plastic off-fault material models has demonstrated the evolution of coseismic off-fault damage during earthquake ruptures. Laboratory scale micro-earthquake experiments have pointed out the enhanced high-frequency radiation due to the coseismic off-fault damage. However, the detailed off-fault fracturing mechanisms, subsequent radiation and its contribution to the overall Energy Budget remain to be fully understood because of limitations of current observational techniques and model formulations. Here, we constructed a new physics-based dynamic earthquake rupture modeling framework, based on the combined finite-discrete element method (FDEM), to investigate the fundamental mechanisms of coseismic off-fault damage, and its effect on the rupture dynamics, the radiation and the overall Energy Budget. We conducted a 2-D systematic case study with depth and showed the mechanisms of dynamic activation of the coseismic off-fault damage. We found the decrease in rupture velocity and the enhanced high-frequency radiation in near-field due to the coseismic off-fault damage. We then evaluated the overall Energy Budget, which shows a significant contribution of the coseismic off-fault damage to the overall Energy Budget even at depth, where the damage zone width becomes narrower. The present numerical framework for the dynamic earthquake rupture modeling thus provides the insight into the earthquake rupture dynamics with the coseismic off-fault damage.
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dynamics radiation and overall Energy Budget of earthquake rupture with coseismic off fault damage
arXiv: Geophysics, 2019Co-Authors: Kurama Okubo, Harsha S Bhat, Esteban Rougier, Samson Marty, Alexandre Schubnel, Earl E Knight, Yann KlingerAbstract:Earthquake ruptures dynamically activate coseismic off-fault damage around fault cores. Systematic field observation efforts have shown the distribution of off-fault damage around main faults, while numerical modeling using elasto-plastic, or homogenised damage, off-fault material models has demonstrated the evolution of coseismic off-fault damage during earthquake ruptures. Laboratory scale micro-earthquake experiments have pointed out the enhanced high-frequency radiation due to the coseismic off-fault damage. However, the detailed off-fault fracturing mechanisms, subsequent radiation and its contribution to the overall Energy Budget remain to be fully understood because of limitations of current observational techniques and model formulations. Here, we constructed a new physics-based dynamic earthquake rupture modeling framework, based on the combined finite-discrete element method (FDEM), to investigate the fundamental mechanisms of coseismic off-fault damage, its effect on rupture dynamics, radiation and overall Energy Budget. We conducted a 2-D systematic case study with depth (using lithosttaic confining pressure as a proxy for depth) and showed the mechanisms of dynamic activation of the coseismic off-fault damage. We found that the rupture velocity decreases and the near-field high-frequency radiation is enhanced due to coseismic off-fault damage. We then evaluated the overall Energy Budget, and show that there is significant contribution of the coseismic off-fault damage to the overall Energy Budget even at depth, where the damage zone width becomes narrower. The present numerical framework for dynamic earthquake rupture modeling thus provides a new insight into earthquake rupture dynamics with coseismic off-fault damage.
F S Mozer - One of the best experts on this subject based on the ideXlab platform.
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wave Energy Budget analysis in the earth s radiation belts uncovers a missing Energy
Nature Communications, 2015Co-Authors: A V Artemyev, O V Agapitov, D Mourenas, V Krasnoselskikh, F S MozerAbstract:Whistler-mode waves regulate trapped electrons in the magnetosphere, but an accurate determination of their Energy Budget has remained elusive. This study presents a full analysis of their magnetic and electric field contributions and finds that a large amount of Energy is stored in oblique waves.
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Wave Energy Budget analysis in the Earth's radiation belts uncovers a missing Energy
Nature Communications, 2015Co-Authors: A V Artemyev, O V Agapitov, D Mourenas, V Krasnoselskikh, F S MozerAbstract:Whistler-mode emissions are important electromagnetic waves pervasive in the Earth's magnetosphere, where they continuously remove or energize electrons trapped by the geomagnetic field, controlling radiation hazards to satellites and astronauts and the upper-atmosphere ionization or chemical composition. Here, we report an analysis of 10-year Cluster data, statistically evaluating the full wave Energy Budget in the Earth's magneto-sphere, revealing that a significant fraction of the Energy corresponds to hitherto generally neglected very oblique waves. Such waves, with 10 times smaller magnetic power than parallel waves, typically have similar total Energy. Moreover, they carry up to 80% of the wave Energy involved in wave–particle resonant interactions. It implies that electron heating and precipitation into the atmosphere may have been significantly under/over-valued in past studies considering only conventional quasi-parallel waves. Very oblique waves may turn out to be a crucial agent of Energy redistribution in the Earth's radiation belts, controlled by solar activity.
Stephane Pouvreau - One of the best experts on this subject based on the ideXlab platform.
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a dynamic Energy Budget deb growth model for pacific oyster larvae crassostrea gigas
Aquaculture, 2010Co-Authors: Benjamin Ricovilla, René Robert, Ismael Bernard, Stephane PouvreauAbstract:Abstract Dynamic Energy Budget (DEB) theory aims to quantify the energetic framework of an individual organism as a dynamic model, from the uptake of food to its utilisation in metabolic processes (maintenance, growth, development and reproduction). The purpose of the present paper is to extend the existing DEB model for adult Pacific oyster Crassostrea gigas to the larval life stage of this species. We present the application of generic DEB theory to oyster larvae, with the formulation of the specific assumptions based on the characteristics of this stage. The model depends on seawater temperature and food density, as forcing variables, followed throughout the whole larval development. We calculated DEB parameter values for larvae by means of laboratory experiments specifically designed to collect datasets on ingestion and growth at different levels of phytoplankton density and temperature. The DEB model developed here showed good growth simulations and provided an extensive description of the energetic needs of C. gigas during its larval stage. It was demonstrated that, at 27 °C, a food density of 1400 µm 3 µl − 1 must be maintained throughout larval development to maximise growth and metamorphosis success. Timing of metamorphosis decreases exponentially with increasing temperature.
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application of a dynamic Energy Budget model to the pacific oyster crassostrea gigas reared under various environmental conditions
Journal of Sea Research, 2006Co-Authors: Stephane Pouvreau, Yves Bourles, Sebastien Lefebvre, Aline Gangnery, Marianne AlunnobrusciaAbstract:The Dynamic Energy Budget (DEB) model (Kooijman, S.A.L.M., 1986. Energy Budgets can explain body size relations. J. Theor. Biol. 121, 269-282; Kooijman, S.A.L.M., 2000. Dynamic Energy and Mass Budgets in Biological Systems. Cambridge University Press, Cambridge, 424 pp.) has been adapted to describe the dynamics of growth and reproduction of the Pacific oyster (Crassostrea gigas) reared in different areas under conditions ranging from controlled to natural. The values of the model parameters were estimated from available physiological data and from published information. The sets of data used to validate the model came from three long-term growth experiments (> 5 months) performed on Pacific oysters reared under different conditions of food and environment. The forcing variables were temperature and phytoplankton densities, the latter being assessed from in vivo fluorescence and chlorophyll-a concentration measurement. The successful validation of the model on the three data sets demonstrated its ability to capture the dynamics of the Energy Budget in the Pacific oyster in various environments with the same set of parameters. The only parameter that varied between simulations was the half-saturation coefficient (XK), because of a different diet composition between the three environments under test. The model successfully reproduced quantitatively the growth and reproduction and the timing of spawning. These first simulation data led us to propose several promising perspectives of application for this model in shellfish ecosystems.
Roger M Nisbet - One of the best experts on this subject based on the ideXlab platform.
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predicting population dynamics from the properties of individuals a cross level test of dynamic Energy Budget theory
The American Naturalist, 2013Co-Authors: Benjamin T Martin, Roger M Nisbet, Tjalling Jager, Thomas G Preuss, Volker GrimmAbstract:Abstract Individual-based models (IBMs) are increasingly used to link the dynamics of individuals to higher levels of biological organization. Still, many IBMs are data hungry, species specific, and time-consuming to develop and analyze. Many of these issues would be resolved by using general theories of individual dynamics as the basis for IBMs. While such theories have frequently been examined at the individual level, few cross-level tests exist that also try to predict population dynamics. Here we performed a cross-level test of dynamic Energy Budget (DEB) theory by parameterizing an individual-based model using individual-level data of the water flea, Daphnia magna, and comparing the emerging population dynamics to independent data from population experiments. We found that DEB theory successfully predicted population growth rates and peak densities but failed to capture the decline phase. Further assumptions on food-dependent mortality of juveniles were needed to capture the population dynamics after...
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integrating dynamic Energy Budget deb theory with traditional bioenergetic models
The Journal of Experimental Biology, 2012Co-Authors: Roger M Nisbet, Marko Jusup, Tin Klanjscek, Laure PecquerieAbstract:Summary Dynamic Energy Budget (DEB) theory offers a systematic, though abstract, way to describe how an organism acquires and uses Energy and essential elements for physiological processes, in addition to how physiological performance is influenced by environmental variables such as food density and temperature. A ‘standard’ DEB model describes the performance (growth, development, reproduction, respiration, etc.) of all life stages of an animal (embryo to adult), and predicts both intraspecific and interspecific variation in physiological rates. This approach contrasts with a long tradition of more phenomenological and parameter-rich bioenergetic models that are used to make predictions from species-specific rate measurements. These less abstract models are widely used in fisheries studies; they are more readily interpretable than DEB models, but lack the generality of DEB models. We review the interconnections between the two approaches and present formulae relating the state variables and fluxes in the standard DEB model to measured bioenergetic rate processes. We illustrate this synthesis for two large fishes: Pacific bluefin tuna ( Thunnus orientalis ) and Pacific salmon ( Oncorhynchus spp.). For each, we have a parameter-sparse, full-life-cycle DEB model that requires adding only a few species-specific features to the standard model. Both models allow powerful integration of knowledge derived from data restricted to certain life stages, processes and environments.
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dynamic Energy Budget theory and population ecology lessons from daphnia
Philosophical Transactions of the Royal Society B, 2010Co-Authors: Roger M Nisbet, Edward Mccauley, Leah R JohnsonAbstract:Dynamic Energy Budget (DEB) theory offers a perspective on population ecology whose starting point is Energy utilization by, and homeostasis within, individual organisms. It is natural to ask what it adds to the existing large body of individual-based ecological theory. We approach this question pragmatically—through detailed study of the individual physiology and population dynamics of the zooplankter Daphnia and its algal food. Standard DEB theory uses several state variables to characterize the state of an individual organism, thereby making the transition to population dynamics technically challenging, while ecologists demand maximally simple models that can be used in multi-scale modelling. We demonstrate that simpler representations of individual bioenergetics with a single state variable (size), and two life stages (juveniles and adults), contain sufficient detail on mass and Energy Budgets to yield good fits to data on growth, maturation and reproduction of individual Daphnia in response to food availability. The same simple representations of bioenergetics describe some features of Daphnia mortality, including enhanced mortality at low food that is not explicitly incorporated in the standard DEB model. Size-structured, population models incorporating this additional mortality component resolve some long-standing questions on stability and population cycles in Daphnia. We conclude that a bioenergetic model serving solely as a ‘regression’ connecting organismal performance to the history of its environment can rest on simpler representations than those of standard DEB. But there are associated costs with such pragmatism, notably loss of connection to theory describing interspecific variation in physiological rates. The latter is an important issue, as the type of detailed study reported here can only be performed for a handful of species.
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sublethal toxicant effects with dynamic Energy Budget theory model formulation
Ecotoxicology, 2010Co-Authors: Erik Muller, Roger M Nisbet, Heather A BerkleyAbstract:We develop and test a general modeling framework to describe the sublethal effects of pollutants by adding toxicity modules to an established dynamic Energy Budget (DEB) model. The DEB model describes the rates of Energy acquisition and expenditure by individual organisms; the toxicity modules describe how toxicants affect these rates by changing the value of one or more DEB parameters, notably the parameters quantifying the rates of feeding and maintenance. We investigate four toxicity modules that assume: (1) effects on feeding only; (2) effects on maintenance only; (3) effects on feeding and maintenance with similar values for the toxicity parameters; and (4) effects on feeding and maintenance with different values for the toxicity parameters. We test the toxicity modules by fitting each to published data on feeding, respiration, growth and reproduction. Among the pollutants tested are metals (mercury and copper) and various organic compounds (chlorophenols, toluene, polycyclic aromatic hydrocarbons, tetradifon and pyridine); organisms include mussels, oysters, earthworms, water fleas and zebrafish. In most cases, the data sets could be adequately described with any of the toxicity modules, and no single module gave superior fits to all data sets. We therefore propose that for many applications, it is reasonable to use the most general and parameter sparse module, i.e. module 3 that assumes similar effects on feeding and maintenance, as a default. For one example (water fleas), we use parameter estimates to calculate the impact of food availability and toxicant levels on the long term population growth rate.
A V Artemyev - One of the best experts on this subject based on the ideXlab platform.
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wave Energy Budget analysis in the earth s radiation belts uncovers a missing Energy
Nature Communications, 2015Co-Authors: A V Artemyev, O V Agapitov, D Mourenas, V Krasnoselskikh, F S MozerAbstract:Whistler-mode waves regulate trapped electrons in the magnetosphere, but an accurate determination of their Energy Budget has remained elusive. This study presents a full analysis of their magnetic and electric field contributions and finds that a large amount of Energy is stored in oblique waves.
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Wave Energy Budget analysis in the Earth's radiation belts uncovers a missing Energy
Nature Communications, 2015Co-Authors: A V Artemyev, O V Agapitov, D Mourenas, V Krasnoselskikh, F S MozerAbstract:Whistler-mode emissions are important electromagnetic waves pervasive in the Earth's magnetosphere, where they continuously remove or energize electrons trapped by the geomagnetic field, controlling radiation hazards to satellites and astronauts and the upper-atmosphere ionization or chemical composition. Here, we report an analysis of 10-year Cluster data, statistically evaluating the full wave Energy Budget in the Earth's magneto-sphere, revealing that a significant fraction of the Energy corresponds to hitherto generally neglected very oblique waves. Such waves, with 10 times smaller magnetic power than parallel waves, typically have similar total Energy. Moreover, they carry up to 80% of the wave Energy involved in wave–particle resonant interactions. It implies that electron heating and precipitation into the atmosphere may have been significantly under/over-valued in past studies considering only conventional quasi-parallel waves. Very oblique waves may turn out to be a crucial agent of Energy redistribution in the Earth's radiation belts, controlled by solar activity.