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München, Germany

Li Y.,TU Munich | Pelties C.,Ludwig Maximilians University of Munich | Kaser M.,Geo Risks Research | Nararan N.,TU Munich
2012 2nd IEEE International Workshop on Requirements Patterns, RePa 2012 - Proceedings

Requirements patterns help reusing the knowledge of capturing required functionalities and properties of a system. To improve requirements engineering in seismological software development, we identify commonly used requirements patterns. This paper introduces research of identifying two main requirements patterns in projects typical for computational seismology, namely, the forward simulation pattern and the data access pattern. They help efficiently and effectively eliciting requirements by providing necessary abstractions. We present a dynamic rupture example to illustrate how to apply both patterns. The patterns can foster a more productive requirements engineering process and sharing software development knowledge within the domain. © 2012 IEEE. Source

Ngwira C.M.,Catholic University of America | Ngwira C.M.,NASA | Pulkkinen A.A.,NASA | Bernabeu E.,PJM Interconnection LLC | And 3 more authors.
Geophysical Research Letters

One of the major challenges pertaining to extreme geomagnetic storms is to understand the basic processes associated with the development of dynamic magnetosphere-ionosphere currents, which generate large induced surface geoelectric fields. Previous studies point out the existence of localized peak geoelectric field enhancements during extreme storms. We examined induced global geoelectric fields derived from ground-based magnetometer recordings for 12 extreme geomagnetic storms between the years 1982 and 2005. For the present study two important extreme storms, 29 October 2003 and 13 March 1989, are shown. The primary purpose of this paper is to provide further evidence on the existence of localized peak geoelectric field enhancements and to show that the structure of the geoelectric field during these localized extremes at single sites can differ greatly from globally and regionally averaged fields. Although the physical processes that govern the development of these localized extremes are still not clear, we discuss some possible causes. ©2015. American Geophysical Union. All Rights Reserved. Source

Coasts attract people and businesses but are also subject to numerous threats from nature. Most of the great natural catastrophes in the last few years happened on coasts. Nowhere else is the potential for huge losses as high as here. The high level of risk is the result not only of an extreme natural hazard situation, but also mainly determined by the enormous concentrations of people and values in coastal regions. The vulnerability of modern complex societies amplifies the risk further. Source

Pulkkinen A.,NASA | Bernabeu E.,PJM Interconnection LLC | Eichner J.,Geo Risks Research | Viljanen A.,Finnish Meteorological Institute | And 2 more authors.
Earth, Planets and Space

Motivated by the needs of the high-voltage power transmission industry, we use data from the high-latitude IMAGE magnetometer array to study characteristics of extreme geoelectric fields at regional scales. We use 10-s resolution data for years 1993-2013, and the fields are characterized using average horizontal geoelectric field amplitudes taken over station groups that span about 500-km distance. We show that geoelectric field structures associated with localized extremes at single stations can be greatly different from structures associated with regionally uniform geoelectric fields, which are well represented by spatial averages over single stations. Visual extrapolation and rigorous extreme value analysis of spatially averaged fields indicate that the expected range for 1-in-100-year extreme events are 3-8 V/km and 3.4-7.1 V/km, respectively. The Quebec reference ground model is used in the calculations. © 2015 Pulkkinen et al.; licensee Springer. Source

Pelties C.,Ludwig Maximilians University of Munich | De La Puente J.,Barcelona Supercomputing Center | Ampuero J.-P.,California Institute of Technology | Brietzke G.B.,German Research Center for Geosciences | Kaser M.,Geo Risks Research
Journal of Geophysical Research: Solid Earth

Accurate and efficient numerical methods to simulate dynamic earthquake rupture and wave propagation in complex media and complex fault geometries are needed to address fundamental questions in earthquake dynamics, to integrate seismic and geodetic data into emerging approaches for dynamic source inversion, and to generate realistic physics-based earthquake scenarios for hazard assessment. Modeling of spontaneous earthquake rupture and seismic wave propagation by a high-order discontinuous Galerkin (DG) method combined with an arbitrarily high-order derivatives (ADER) time integration method was introduced in two dimensions by de la Puente et al. (2009). The ADER-DG method enables high accuracy in space and time and discretization by unstructured meshes. Here we extend this method to three-dimensional dynamic rupture problems. The high geometrical flexibility provided by the usage of tetrahedral elements and the lack of spurious mesh reflections in the ADER-DG method allows the refinement of the mesh close to the fault to model the rupture dynamics adequately while concentrating computational resources only where needed. Moreover, ADER-DG does not generate spurious high-frequency perturbations on the fault and hence does not require artificial Kelvin-Voigt damping. We verify our three-dimensional implementation by comparing results of the SCEC TPV3 test problem with two well-established numerical methods, finite differences, and spectral boundary integral. Furthermore, a convergence study is presented to demonstrate the systematic consistency of the method. To illustrate the capabilities of the high-order accurate ADER-DG scheme on unstructured meshes, we simulate an earthquake scenario, inspired by the 1992 Landers earthquake, that includes curved faults, fault branches, and surface topography. Copyright 2012 by the American Geophysical Union. Source

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