Probabilistic seismic hazard maps from seismicity patterns analysis: the Iberian Peninsula case

Earthquake prediction is a main topic in Seismology. Here, the goal is to know the correlation between the seismicity at a certain place at a given time with the seismicity at the same place, but at a following interval of time. There are no ways for exact predictions, but one can wonder about the causality relations between the seismic characteristics at a given time interval and another in a region. In this paper, a new approach to this kind of studies is presented. Tools which include cellular automata theory and Shannon's entropy are used. First, the catalogue is divided into time intervals, and the region into cells. The activity or inactivity of each cell at a certain time is described using an energy criterion; thus a pattern which evolves over time is given. The aim is to find the rules of the stochastic cellular automaton which best fits the evolution of the pattern. The neighborhood utilized is the cross template (CT). A grid search is made to choose the best model, being the mutual information between the different times the function to be maximized. This function depends on the size of the cells β on and the interval of time τ which is considered for studying the activity of a cell. With these β and τ, a set of probabilities which characterizes the evolution rules is calculated, giving a probabilistic approach to the spatiotemporal evolution of the region. The sample catalogue for the Iberian Peninsula covers since 1970 till 2001. The results point out that the seismic activity must be deduced not only from the past activity at the same region but also from its surrounding activity. The time and spatial highest interaction for the catalogue used are of around 3.3 years and 290x165 km², respectively; if a cell is inactive, it will continue inactive with a high probability; an active cell has around the 60% probability of continuing active in the future. The Probabilistic Seismic Hazard Map obtained marks the main seismic active areas (northwestern Africa) were the real seismicity has been occurred after the date of the data set studied. Also, the Hurst exponent has been studied. The value calculated is 0.48±0.02, which means that the process is inherently unpredictable. This result can be related to the incapacity of the cellular automaton obtained of predicting sudden changes

Fractal behaviour of the seismicity in the Southern Iberian Peninsula

The fractal behaviour of the seismicity in the Southern Iberian Peninsula is analysed by considering two different series of data: the distance and the elapsed time between consecutive seismic events recorded by the seismic network of the Andalusian Institute of Geophysics (AIG). The fractal analyses have been repeated by considering four threshold magnitudes of 2.5, 3.0, 3.5 and 4.0. The re-scaled analysis lets to determine if the seismicity shows strong randomness or if it is characterised by time-persistence and the cluster dimension indicates the degree of time and spatial clustering of the seismicity. Another analysis, based on the reconstruction theorem, permits to evaluate the minimum number of nonlinear equations describing the dynamical mechanism of the seismicity, its 'loss of memory', its chaotic character and the instability of a possible predicting algorithm. The results obtained depict some differences depending on distances or elapsed times and the different threshold levels of magnitude also lead to slightly different results. Additionally, only a part of the fractal tools, the re-scaled analysis, have been applied to five seismic crises in the same area

Statistical distribution of elapsed times and distances of seismic events: the case of the Southern Spain seismic catalogue

International audienceSeveral empiric cumulative distributions of elapsed times and distances between seismic events occurred in the Southern Iberian Peninsula from 1985 to 2000 (data extracted from the seismic catalogue of the Andalusian Institute of Geophysics) are investigated. Elapsed times and distances between consecutive seismic events of the whole catalogue, taking into account threshold magnitudes of 2.5, 3.0, 3.5 and 4.0, and of five seismic crises, without distinguishing magnitudes, are investigated. Additionally, the series of distances and elapsed times from the main event to every aftershock are also analysed for the five seismic crises. Even though a power law is sometimes a satisfactory model for the cumulative distribution of elapsed times and distances between seismic events, in some cases a fit with a Weibull distribution for elapsed times performs better. It is worth of mention that, in the case of the seismic crises, the fit achieved by the power law is sometimes improved when it is combined with a logarithmic law. The results derived might be a contribution to a better representation of the seismic activity by means of models that could be based on random-walk processes

A probabilistic seismic hazard model based on cellular automata and information theory

International audienceWe try to obtain a spatio-temporal model of earthquakes occurrence based on Information Theory and Cellular Automata (CA). The CA supply useful models for many investigations in natural sciences; here, it have been used to establish temporal relations between the seismic events occurring in neighbouring parts of the crust. The catalogue used is divided into time intervals and the region into cells, which are declared active or inactive by means of a certain energy release criterion (four criteria have been tested). A pattern of active and inactive cells which evolves over time is given. A stochastic CA is constructed with the patterns to simulate their spatio-temporal evolution. The interaction between the cells is represented by the neighbourhood (2-D and 3-D models have been tried). The best model is chosen by maximizing the mutual information between the past and the future states. Finally, a Probabilistic Seismic Hazard Map is drawn up for the different energy releases. The method has been applied to the Iberian Peninsula catalogue from 1970 to 2001. For 2-D, the best neighbourhood has been the Moore's one of radius 1; the von Neumann's 3-D also gives hazard maps and takes into account the depth of the events. Gutenberg-Richter's law and Hurst's analysis have been obtained for the data as a test of the catalogue. Our results are consistent with previous studies both of seismic hazard and stress conditions in the zone, and with the seismicity occurred after 2001

High-Mobility Few-Layer Graphene Field Effect Transistors Fabricated on Epitaxial Ferroelectric Gate Oxides

The carrier mobility \mu of few-layer graphene (FLG) field-effect transistors increases ten-fold when the SiO_2 substrate is replaced by single-crystal epitaxial Pb(Zr_0.2Ti_0.8)O_3 (PZT). In the electron-only regime of the FLG, \mu reaches 7x10^4 cm^2/Vs at 300K for n = 2.4x10^12/cm^2, 70% of the intrinsic limit set by longitudinal acoustic (LA) phonons; it increases to 1.4x10^5 cm^2/Vs at low temperature. The temperature-dependent resistivity \rho(T) reveals a clear signature of LA phonon scattering, yielding a deformation potential D = 7.8+/-0.5 eV.Comment: 5 pages, 4 figure

El planteamiento de problemas y la construcción del Teorema de Bayes

Las tareas de resolución y planteamiento de problemas posibilitan indagar sobre aprendizajes específicos de los estudiantes. Plantear un problema significa idear un problema preconcibiendo un plan para su resolución. En la actualidad, sabemos poco de los procesos cognitivos usados por los estudiantes que pueden ser efectivos para plantear problemas de matemáticas. Para dar cuenta de cómo estudiantes universitarios construyen conocimiento relativo al teorema de Bayes cuando realizan tareas de planteamiento de problemas, usamos el modelo de la abstracción en contexto de acciones epistémicas anidadas de Hershkowitz, Schwarz y Dreyfus (2001). Los resultados muestran características distintas en el proceso de construcción del teorema de Bayes que ponen de manifiesto el potencial de las tareas de plantear problemas para desencadenar procesos de abstracción.Problem posing and problem solving are suitable tasks for inquiring into the learning of specific concepts. Posing a problem involves setting up a text for the problem and thinking about a plan to solve it. Currently, we have scarce knowledge about students' effective cognitive process when posing mathematical problems. We have used the theoretical framework of nested epistemic actions (Hershkowitz, Schwarz and Dreyfus, 2001) in order to study how university students built knowledge about Bayes' Theorem when they solve problem posing tasks. We have identified different characteristics in the process of constructing Bayes' Theorem and the potential of posing problem activities to generate the abstraction process

An Ising model for earthquake dynamics

This paper focuses on extracting the information contained in seismic space-time patterns and their dynamics. The Greek catalog recorded from 1901 to 1999 is analyzed. An Ising Cellular Automata representation technique is developed to reconstruct the history of these patterns. We find that there is strong correlation in the region, and that small earthquakes are very important to the stress transfers. Finally, it is demonstrated that this approach is useful for seismic hazard assessment and intermediate-range earthquake forecasting

Probabilistic seismic hazard maps from seismicity patterns analysis: the Iberian Peninsula case

International audienceEarthquake prediction is a main topic in Seismology. Here, the goal is to know the correlation between the seismicity at a certain place at a given time with the seismicity at the same place, but at a following interval of time. There are no ways for exact predictions, but one can wonder about the causality relations between the seismic characteristics at a given time interval and another in a region. In this paper, a new approach to this kind of studies is presented. Tools which include cellular automata theory and Shannon's entropy are used. First, the catalogue is divided into time intervals, and the region into cells. The activity or inactivity of each cell at a certain time is described using an energy criterion; thus a pattern which evolves over time is given. The aim is to find the rules of the stochastic cellular automaton which best fits the evolution of the pattern. The neighborhood utilized is the cross template (CT). A grid search is made to choose the best model, being the mutual information between the different times the function to be maximized. This function depends on the size of the cells ? on and the interval of time ? which is considered for studying the activity of a cell. With these ? and ?, a set of probabilities which characterizes the evolution rules is calculated, giving a probabilistic approach to the spatiotemporal evolution of the region. The sample catalogue for the Iberian Peninsula covers since 1970 till 2001. The results point out that the seismic activity must be deduced not only from the past activity at the same region but also from its surrounding activity. The time and spatial highest interaction for the catalogue used are of around 3.3 years and 290x165 km2, respectively; if a cell is inactive, it will continue inactive with a high probability; an active cell has around the 60% probability of continuing active in the future. The Probabilistic Seismic Hazard Map obtained marks the main seismic active areas (northwestern Africa) were the real seismicity has been occurred after the date of the data set studied. Also, the Hurst exponent has been studied. The value calculated is 0.48±0.02, which means that the process is inherently unpredictable. This result can be related to the incapacity of the cellular automaton obtained of predicting sudden changes

QoS-Based Middleware Architecture for Distributed Control Systems

The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-540-85863-8_70This paper presents an implementation of a middleware architecture to control distributed systems. The main objective is providing a QoS level between the communications layer and the control layer. This architecture is based on the use of a hierarchical communications structure called logical namespace tree and a structured set of control processes interconnected, called logical sensors graph . This architecture is named Frame Sensor Adapter Control (FSA-Ctrl). In this architecture communication layer and control layer can manage the QoS policies. The communication layer is based on the Data Distribution Service (DDS), a standard proposed by Object Management Group (OMG). Control layer is derived from the Sensor Web Enablement (SWE) model proposed by Open Geospatial Consortium (OGC). Middleware components use messages queues to manage components QoS requirements. By means of QoS policies, control components can take important decisions about distributed questions, like components mobility or information redundancy detection.The architecture described in this article is a part of the coordinated project KERTROL: Kernel control on embedded system strongly connected. Education and Science Department, Spanish Government. CICYT: DPI2005-09327-C02-01/02.Poza-Lujan, J.; Posadas-Yagüe, J.; Simó Ten, JE. (2009). QoS-Based Middleware Architecture for Distributed Control Systems. En International Symposium on Distributed Computing and Artificial Intelligence 2008 (DCAI 2008). Springer. 587-595. https://doi.org/10.1007/978-3-540-85863-8_70S587595Matteucci, M.: Publish/Subscribe Middleware for Robotics: Requirements and State of the Art. Technical Report N 2003.3, Politecnico di Milano, Milano, Italy (2003)OMG. Data Distribution Service for Real-Time Systems, v1.1. Document formal/2005-12-04 (2005)Botts, M., Percivall, G., Reed, C., Davidson, J. (eds.): OGC. Sensor Web Enablement: Overview and High Level Architecture. OGC White Paper. OGC 06-050r2 (2006)Coulouris, G., Dollimore, J., Kindberg, T.: Distributed systems, concepts and design, 3rd edn. Addison-Wesley, Reading (2001)OMG. Real-Time Corba Specification version 1.1. Document formal /02-08-02 (2002)FIPA. Specfication. Part 2, Agent Communication Language. Foundation for Intelligent Physical Agents (1997)Hapner, M., Sharma, R., Fialli, J., Stout, K.: JMS specification, vol. 1.1. Sun Microsystems Inc., Santa Clara (2002)Pardo-Castellote, G.: OMG Data-Distribution Service: architectural overview. In: Proceedings of 23rd International Conference on Distributed Computing Systems Workshops, Providence, USA, vol. 19-22, pp. 200–206 (2003)Vogel, A., Kerherve, B., von Bochmann, G., Gecsei, J.: Distributed Multimedia and QoS: A Survey. IEEE Multimedia 2(2), 10–19 (1995)Crawley, E., Nair, R., Rajagopalan, B.: RFC 2386: A Framework for QoS-based Routing in the Internet. IETF Internet Draft, pp. 1–37 (1998)Botts, M., Percivall, G., Reed, C., Davidson, J.: OGC. Sensor Web Enablement: Overview and High Level Architecture. OpenGIS Consortium Inc. (2006)Posadas, J.L., Perez, P., Simo, J.E., Benet, G., Blanes, F.: Communication structure for sensory data in mobile robots. Engineering Applications of Artificial Intelligence 15(3-4), 341–350 (2002)Poza, J.L., Posadas, J.L., Simó, J.E., Benet, G.: Hierarchical communication system to manage maps in mobile robot navigation. In: Proceedings of International Conference on Automation, Control and Instrumentation, Valencia, Spain (2006)Poza, J.L., Posadas, J.L., Simó, J.E.: Distributed agent specification to an Intelligent Control Architecture. In: 6th International Workshop on Practical Applications of Agents and Multiagent Systems, Salamanca, Spain (in press, 2007

Ideal barriers to polarization reversal and domain-wall motion in strained ferroelectric thin films

The ideal intrinsic barriers to domain switching in c-phase PbTiO_3 (PTO), PbZrO_3 (PZO), and PbZr_{1-x}Ti_xO_3 (PZT) are investigated via first-principles computational methods. The effects of epitaxial strain on the atomic structure, ferroelectric response, barrier to coherent domain reversal, domain-wall energy, and barrier to domain-wall translation are studied. It is found that PTO has a larger polarization, but smaller energy barrier to domain reversal, than PZO. Consequentially the idealized coercive field is over two times smaller in PTO than PZO. The Ti--O bond length is more sensitive to strain than the other bonds in the crystals. This results in the polarization and domain-wall energy in PTO having greater sensitivity to strain than in PZO. Two ordered phases of PZT are considered, the rock-salt structure and a (100) PTO/PZO superlattice. In these simple structures we find that the ferroelectric properties do not obey Vergard's law, but instead can be approximated as an average over individual 5-atom unit cells.Comment: 9 pages, 13 figure