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Papers by K. Fleming

Risk analysis for natural hazards is usually carried out separately for the various pertinent haz... more Risk analysis for natural hazards is usually carried out separately for the various pertinent hazards in the considered regions or cities, often without attempting to combine these studies into a holistic risk assessment. However, effective decision making requires comprehensive information that includes all relevant hazard types within a region. In addition to the existing multi-risk approaches, this report aims to compare the single-type risk approaches and to identify their commonalities and differences and to identify existing or potential interfaces. Therefore, a literature review on single-type risk analysis rocedures considering earthquakes, meteorological extremes, wildfires, precipitation, iver floods, storm surges, landslides and volcanic risks has been undertaken. In articular, the scope of the reviews has been narrowed to the spatial scale of cities, to direct damages (economic and loss of life) and to state-of-the-art approaches with a strong focus on quantitative risk ...

Journal of Geophysical Research, 2010

We analyze 2006-2009 data from four continuous Global Positioning System (GPS) receivers located ... more We analyze 2006-2009 data from four continuous Global Positioning System (GPS) receivers located between 5 and 150 km from the glacier Jakobshavn Isbrae, West Greenland. The GPS stations were established on bedrock to determine the vertical crustal motion due to the unloading of ice from Jakobshavn Isbrae. All stations experienced uplift, but the uplift rate at Kangia North, only 5 km from the glacier front, was about 10 mm yr −1 larger than the rate at Ilulissat, located only ∼45 km further away. This suggests that most of the uplift is due to the unloading of the Earth's surface as Jakobshavn thins and loses mass. Our estimate of Jakobshavn's contribution to uplift rates at Kangia North and Ilulissat are 14.6 ± 1.7 mm yr −1 and 4.9 ± 1.1 mm yr −1 , respectively. The observed rates are consistent with a glacier thinning model based on repeat altimeter surveys from NASA's Airborne Topographic Mapper (ATM), which shows that Jakobshavn lost mass at an average rate of 22 ± 2 km 3 yr −1 between 2006 and 2009. At Kangia North and Ilulissat, the predicted uplift rates computed using thinning estimates from the ATM laser altimetry are 12.1 ± 0.9 mm yr −1 and 3.2 ± 0.3 mm yr −1 , respectively. The observed rates are slightly larger than the predicted rates. The fact that the GPS uplift rates are much larger closer to Jakobshavn than further away, and are consistent with rates inferred using the ATM-based glacier thinning model, shows that GPS measurements of crustal motion are a potentially useful method for assessing ice-mass change models.

The Gravity Recovery and Climate Experiment (GRACE) has so far seen around 4 years worth of month... more The Gravity Recovery and Climate Experiment (GRACE) has so far seen around 4 years worth of monthly gravity-field solutions being released to the scientific community. These are provided in the form of Stokes potential coefficients by the GRACE Science Data Service centers; the Center for Space Research, University of Texas (CSR), the GeoForschungsZentrum Potsdam (GFZ) and the Jet Propulsion Laboratory

We estimate the ice-mass loss in West Antarctica from the Gravity Recovery and Climate Experiment... more We estimate the ice-mass loss in West Antarctica from the Gravity Recovery and Climate Experiment (GRACE) using the following approach. First, we predict the gravity-field change over Antarctica arising from present-day ice-mass changes, mainly derived from satellite altimetry, and the ongoing glacial-isostatic adjustment (GIA), which is computed by subjecting a viscoelastic earth model to a thermomechanical reconstruction of Antarctica's late-Pleistocene

ABSTRACT The distribution and amount of potential losses due natural hazards are continuously, an... more ABSTRACT The distribution and amount of potential losses due natural hazards are continuously, and sometimes abruptly varying, spatially and temporally. Changes in damage distribution are dependent both on the specific natural hazard (for instance flood hazard can depend on the season and on the weather) and on the evolution of vulnerability (in terms of variation in size and composition of the exposed assets). Considering space and time, moreover, the most appropriate scales at which the changes occur have to be taken into account. Furthermore, spatio-temporal variability of multi-risk assessment is depending on the distribution and quality of the information upon which the assessment is made. This information is subject to uncertainties that also vary over time, for instance as new data are collected and integrated. Multi-risk assessment is therefore a dynamical process aiming for a continuous monitoring of the expected consequences of the occurring of one or more natural events, given an uncertain and incomplete description of both the involved hazards and the composition and vulnerability of the exposed assets. A novel multi-resolution, adaptive data collection approach is explored, which is of particular interest in countries where multi-scale, multi-risk assessment is sought but limited resources are available for intensive exposure and vulnerability data collection. In this case a suitable prioritisation of data collection is proposed as an adaptive sampling scheme optimized to trade off between data collection cost and loss estimation uncertainty. Preliminary test cases will be presented and discussed.

The Self-Organizing Seismic Early Warning Information Network (SOSEWIN) represents a new approach... more The Self-Organizing Seismic Early Warning Information Network (SOSEWIN) represents a new approach for Earthquake Early Warning Systems (EEWS), consisting in taking advantage of novel wireless communications technologies. It also sets out to overcome problems of insufficient node density, which typically affects present existing early warning systems, by having the SOSEWIN seismological sensing units being comprised of low-cost components (generally bought

gfz-potsdam.de

Throughout the ages, earthquakes have been among the most disastrous natural phenomena, destroyin... more Throughout the ages, earthquakes have been among the most disastrous natural phenomena, destroying cities, killing human beings, and today threatening millions of people all over the world. Due to the rapid growth and development of urban settlements, ...

Journal of Geophysical Research, 2006

We analyze the Venusian geoid and topography to determine the relative importance of isostatic, e... more We analyze the Venusian geoid and topography to determine the relative importance of isostatic, elastic and dynamic compensation mechanisms over different degree ranges. The geoid power spectrum plotted on a log-log scale shows a significant change in its slope at about degree 40, suggesting a transition from a predominantly dynamic compensation mechanism at lower degrees to an isostatic and/or elastic mechanism at higher degrees. We focus on the dynamic compensation in the lower-degree interval. We assume that (1) the flow is whole mantle in style, (2) the long-wavelength geoid and topography are of purely dynamic origin, and (3) the density structure of Venus' mantle can be approximated by a model in which the mass anomaly distribution does not vary with depth. Solving the inverse problem for viscosity within the framework of internal loading theory, we determine the families of viscosity models that are consistent with the observed geoid and topography between degrees 2 and 40. We find that a good fit to the data can be obtained not only for an isoviscous mantle without a pronounced lithosphere, as suggested in some previous studies, but also for models with a high-viscosity lithosphere and a gradual increase in viscosity with depth in the mantle. The overall viscosity increase across the mantle found for the latter group of models is only partially resolved, but profiles with a $100-km-thick lithosphere and a viscosity increasing with depth by a factor of 10-80, hence similar to viscosity profiles expected in the Earth's mantle, are among the best fitting models.

Mass changes in the polar regions are inferred by making use of about 4 years of Gravity Recovery... more Mass changes in the polar regions are inferred by making use of about 4 years of Gravity Recovery and Climate Experiment (GRACE) gravity fields. The time series of each of the Stokes coefficients are decomposed into their linear, annual and semi-annual components, and we apply the Student's t-test to assess the statistical significance of the linear temporal trends in the Stokes potential coefficients. We solve the inverse-gravimetric problem by adjusting forward models describing the prominent geoid-height changes arising from ice-mass changes in Antarctica, Greenland, Alaska and Patagonia, and of the glacial-isostatic adjustment (GIA) due to the last glacial-interglacial transition. We show that, although all used data sets (GFZ, CSR; JPL and CNES) consistently reflect the prominent mass changes, differences in the mass-change estimates are considerably larger than the uncertainties estimated by the propagation of the GRACE errors. We then use the bootstrapping method based o...

Journal of Geophysical Research, 2012

Journal of Geophysical Research: Earth Surface, 2011

Geophysical Research Letters, 2012

Geophysical Research Letters, 2004

Bulletin of Earthquake Engineering, 2010

Abstract Rapid improvements in telemetry technology and the general decrease in communication cos... more Abstract Rapid improvements in telemetry technology and the general decrease in communication costs have raised a growing interest in low-cost wireless sensing units. This is especially the case for structural monitoring purposes, where they are becoming a more ...

Natural Hazards and Earth System Sciences Discussions, 2013

Both aleatory and epistemic uncertainties associated with different sources and components of ris... more Both aleatory and epistemic uncertainties associated with different sources and components of risk (hazard, exposure, vulnerability) are present at each step of seismic risk assessments. All individual sources of uncertainty contribute to the total uncertainty, which might be very high and, within the decision-making context, may therefore lead to either very conservative and expensive decisions or the perception of considerable risk. When anatomizing the structure of the total uncertainty, it is therefore important to propagate the different individual uncertainties through the computational chain and to quantify their contribution to the total value of risk. The present study analyses different uncertainties associated with the hazard, vulnerability and loss components by the use of logic trees. The emphasis is on the analysis of epistemic uncertainties, which represent the reducible part of the total uncertainty, including a sensitivity analysis of the resulting seismic risk assessments with regard to the different uncertainty sources. This investigation, being a part of the EU FP7 project MATRIX (New Multi-Hazard and Multi-Risk Assessment Methods for Europe), is carried out for the example of, and with reference to, the conditions of the city of Cologne, Germany, which is one of the MATRIX test cases. At the same time, this particular study does not aim to revise nor to refine the hazard and risk level for Cologne; it is rather to show how large are the existing uncertainties and how they can influence seismic risk estimates, especially in less wellstudied areas, if hazard and risk models adapted from other regions are used.

The number of people affected by natural hazards is growing, as many regions of the world become ... more The number of people affected by natural hazards is growing, as many regions of the world become subject to multiple hazards. Although volume of geophysical, sociological and economic knowledge is increasing, so are the losses from natural catastrophes. The slow transfer from theory to practice might lay in the difficulties of the communication process from science to policy-making, including perceptions by stakeholders from disaster mitigation practice regarding the usability of developed tools. As scientific evidence shows, decision-makers are faced with the challenge of not only mitigating against single hazards and risks, but also multiple risks, which must include the consideration of their interrelations. As the multi-hazard and risk concept is a relatively young area of natural risk governance, there are only a few multi-risk models and the experience of practitioners as to how to use these models is limited. To our knowledge, scientific literature on stakeholders 0 perceptions of multi-risk models is lacking. In this article we identify perceptions of two decision-making tools, which involve multi-hazard and multi-risk. The first one is a generic, multi-risk framework based on the sequential Monte Carlo method to allow for a straightforward and flexible implementation of hazard interactions, which may occur in a complex system. The second is a decision-making tool that integrates direct input from stakeholders by attributing weights to different components and constructing risks ratings. Based on the feedback from stakeholders, we found that interest in multi-risk assessment is high but that its application remains hampered by the complexity of processes involved.