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Guse B.,German Research Center for Geosciences | Guse B.,Center for Disaster Management and Risk Reduction Technology | Guse B.,University of Kiel | Hofherr T.H.,Center for Disaster Management and Risk Reduction Technology | And 3 more authors.
Hydrology and Earth System Sciences | Year: 2010

A novel approach to consider additional spatial information in flood frequency analyses, especially for the estimation of discharges with recurrence intervals larger than 100 years, is presented. For this purpose, large flood quantiles, i.e. pairs of a discharge and its corresponding recurrence interval, as well as an upper bound discharge, are combined within a mixed bounded distribution function. The large flood quantiles are derived using probabilistic regional envelope curves (PRECs) for all sites of a pooling group. These PREC flood quantiles are introduced into an at-site flood frequency analysis by assuming that they are representative for the range of recurrence intervals which is covered by PREC flood quantiles. For recurrence intervals above a certain inflection point, a Generalised Extreme Value (GEV) distribution function with a positive shape parameter is used. This GEV asymptotically approaches an upper bound derived from an empirical envelope curve. The resulting mixed distribution function is composed of two distribution functions which are connected at the inflection point. This method is applied to 83 streamflow gauges in Saxony/Germany. Our analysis illustrates that the presented mixed bounded distribution function adequately considers PREC flood quantiles as well as an upper bound discharge. The introduction of both into an at-site flood frequency analysis improves the quantile estimation. A sensitivity analysis reveals that, for the target recurrence interval of 1000 years, the flood quantile estimation is less sensitive to the selection of an empirical envelope curve than to the selection of PREC discharges and of the inflection point between the mixed bounded distribution function. © 2010 Author(s).

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 | Year: 2012

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.

Hofherr T.,Geo Risks Research | Hofherr T.,Karlsruhe Institute of Technology | Kunz M.,Karlsruhe Institute of Technology
Climate Research | Year: 2010

A method for the assessment of the local hazard caused by large-scale winter storms is described in detail and applied to all of Germany. Spatially highly resolved wind fields of severe storm events in the climatological period from 1971 to 2000 are modeled by a statistical-dynamical downscaling approach with the Karlsruhe Atmospheric Mesoscale Model KAMM, using both ERA-40 re-analysis and observation data. Hazard curves, including quantification of the uncertainties, are determined for all grid points with a distance of 1 km from the modeled wind fields by applying extreme value statistics. The hazard maps reveal critical regions with potentially extreme wind speeds depending on exposure, terrain height and land use. For an exceedance probability of 0.05 yr -1 that equals a return period of 20 yr, the maximum gusts range between 26 m s-1 in deep valleys and >45 m s-1 near the coast as well as over the crests of the low mountain ranges. Particularly saddles, edges, flanks and summits feature a higher hazard for extreme wind speeds. Comparisons of model data and observations confirm the applicability and the high precision of the method. © Inter-Research 2010.

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 | Year: 2015

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.

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 | Year: 2015

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.

Kron W.,Geo Risks Research
WasserWirtschaft | Year: 2010

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.

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 | Year: 2012

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.

Kron W.,Geo Risks Research | Steuer M.,Geo Risks Research | Low P.,Geo Risks Research | Wirtz A.,Geo Risks Research
Natural Hazards and Earth System Science | Year: 2012

Global reinsurer Munich Re has been collecting data on losses from natural disasters for almost four decades. Together with EM-Dat and sigma, Munich Re's NatCatSERVICE database is currently one of three global databases of its kind, with its more than 30 000 datasets. Although the database was originally designed for reinsurance business purposes, it contains a host of additional information on catastrophic events. Data collection poses difficulties such as not knowing the exact extent of human and material losses, biased reporting by interest groups, including governments, changes over time due to new findings, etc. Loss quantities are often not separable into different causes, e.g., windstorm and flood losses during a hurricane, or windstorm, hail and flooding during a severe storm event. These difficulties should be kept in mind when database figures are analysed statistically, and the results have to be treated with due regard for the characteristics of the underlying data. Comparing events at different locations and on different dates can only be done using normalised data. For most analyses, and in particular trend analyses, socio-economic changes such as inflation or growth in population and values must be considered. Problems encountered when analysing trends are discussed using the example of floods and flood losses. © 2012 Author(s) CC Attribution 3.0 License.

Wenk S.,Ludwig Maximilians University of Munich | Pelties C.,Ludwig Maximilians University of Munich | Igel H.,Ludwig Maximilians University of Munich | Kaser M.,Geo Risks Research
Solid Earth | Year: 2013

We present an application of the discontinuous Galerkin (DG) method to regional wave propagation. The method makes use of unstructured tetrahedral meshes, combined with a time integration scheme solving the arbitrary high-order derivative (ADER) Riemann problem. This ADER-DG method is high-order accurate in space and time, beneficial for reliable simulations of high-frequency wavefields over long propagation distances. Due to the ease with which tetrahedral grids can be adapted to complex geometries, undulating topography of the Earth's surface and interior interfaces can be readily implemented in the computational domain. The ADER-DG method is benchmarked for the accurate radiation of elastic waves excited by an explosive and a shear dislocation source. We compare real data measurements with synthetics of the 2009 L'Aquila event (central Italy). We take advantage of the geometrical flexibility of the approach to generate a European model composed of the 3-D EPcrust model, combined with the depth-dependent ak135 velocity model in the upper mantle. The results confirm the applicability of the ADER-DG method for regional scale earthquake simulations, which provides an alternative to existing methodologies. © 2013 Author(s).

News Article | January 4, 2016
Site: phys.org

Natural disasters claimed 23,000 lives last year, substantially more than the previous year's figure of 7,700. However, the number of victims was still less than half the annual average for the last 30 years of 54,000, Munich Re said in a statement. "2015 saw the lowest losses of any year since 2009," the statement said. "Overall losses totalled $90 billion, down from $110 billion the previous year." Of the total overall losses, roughly $27 billion was insured in 2015, compared with $31 billion in 2014. "In terms of financial losses, we were somewhat fortunate in 2015: Strong tropical cyclones frequently only hit sparsely populated areas or did not make landfall at all," said Peter Hoeppe, head of Munich Re's Geo Risks Research Unit. "However, the comparatively low losses are no reason to become complacent," he warned. The year's most devastating natural catastrophe was the earthquake in Nepal, which occurred on April 25, northwest of the capital Kathmandu and reached a magnitude of 7.8. Around 9,000 people were killed and 500,000 were made homeless as a result of the earthquake, Munich Re said. "As is so often the case in developing countries, only a fraction of the $4.8 billion in overall losses caused by the quake and the aftershocks was insured—just $210 million," it added. For the insurance industry, the costliest natural catastrophe in 2015 was the series of winter storms that struck the northeastern United States and Canada in February. Here, insured losses came to $2.1 billion and overall losses totalled $2.8 billion, Munich Re said. Some 94 percent of loss-relevant natural catastrophes in 2015 were weather-related events, Munich Re added.

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