An improved glimpse into earthquake activity in northeastern Alaska

The northeastern Brooks Range is long known to be seismically active, but meaningful analysis of the earthquake activity has been limited by the lack of instrumentation. The seismic record in the area dates back to the mid-1970s, and shows a broad northeast-trending zone of earthquake activity. Improvements made in the past 20 years to the permanent seismic network along with new data collected by the temporary USArray network of seismometers located throughout northeastern Alaska have dramatically lowered the earthquake detection threshold in the area. It is now possible to identify patterns within the earthquake data including spatial distribution and occurrence rates, which indicate the presence of previously unrecognized active fault systems. I highlight several such features within the data: a 110 km (60 mi) line of recurring earthquakes near the village of Beaver that strongly suggest a singular fault system; a cluster of earthquakes near the village of Venetie that are likely occurring on a complex active fault system; a years-long mainshock-aftershock sequence of earthquakes near the Draanjik River that began in 2006; and two swarms separated by 50 km (30 mi) in distance and 7 years near the Hulahula River.Ye

A spatial exploratory model of rural land prices

The land market in the Netherlands seems to get much attention the last few years. Increasing land use pressure caused by a high population density and an increasing economic growth and prosperity result in competing land use claims from a range of sectors. Strict planning schemes segment the land market into sub markets and create an artificial scarcity of land for some land use types, which results in large price differences between the segments. Decisions of the government for designating housing areas, creating nature areas and expanding infrastructure aim at optimal land use with the least negative externalities, but result sometimes in speculation or unwanted situations on the land market. Additionally, the impact of European policies on the land market is still increasing. This raises discussions on the functioning of the land market. In order to get a better understanding of the land market, this study aims at developing a GIS-based explanatory model for rural land prices. Factors that affect rural land prices are collected, analysed, categorised, and used to explain spatial differences in prices of parcels of land in rural areas. Special attention is paid to modelling the effect of governmental policies like zoning and taxing can be analysed with the model. The current model is based on data for the province of Noord-Brabant in the southern part of the Netherlands. For this province data on parcel level is available. Using a geographical information system (GIS) this data can be combined with a rich set of spatial data. The resulting model can be used to carry out case studies like studying the effect of relocation of farmers or the effect of land purchases by the government.

Incentives and the Sorting of Altruistic Agents into Street-Level Bureaucracies

Many street-level bureaucrats (such as caseworkers) have the dual task of helping some clients, while sanctioning others. We develop a model of such a street-level bureaucracy and study the implications of its personnel policy on the self-selection and allocation decisions of agents who differ in altruism towards clients. When bureaucrats are paid flat wages, they do not sanction, and the most altruistic types sort into bureaucracy. Pay-for-performance induces some bureaucrats to sanction, but necessitates an increase in expected wage compensation, which can result in sorting from both the top and bottom of the altruism distribution. We also show how client composition affects sorting and why street-level bureaucrats often experience an overload of clients.street-level bureaucracy, sorting, altruism, personnel policy, pay-for-performance

Litter Quality of Populus Species as Affected by Free-Air CO2

The effect of elevated CO2 and nitrogen fertilization on the molecular chemistry of litter of three Populus species and associated soil organic matter (SOM) was investigated by pyrolysis-gas chromatography/mass spectrometry. The results are based on 147 quantified organic compounds in 24 litter samples. Litter of P. euramerica was clearly different from that of P. nigra and P. alba. The latter two had higher contents of proteins, polysaccharides, and cutin/cutan, while the former had higher contents of phenols and benzofurans/pyrans. The difference between replications was at least as large as the effect of treatments, so that no systematic chemical changes were attributable to CO2 effect or N-fertilization effect. The chemistry of SOM under the various species and treatments did not show significant changes either. The low number of available replicates that is two was clearly insufficient to overcome the effect of spatial variation on litter chemistry and detect small differences in molecular litter chemistry

Volcano Seismicity in Alaska

Thesis (Ph.D.) University of Alaska Fairbanks, 2013I examine the many facets of volcano seismicity in Alaska: from the short-lived eruption seismicity that is limited to only the few weeks during which a volcano is active, to the seismicity that occurs in the months following an eruption, and finally to the longterm volcano seismicity that occurs in the years in which volcanoes are dormant. I use the rich seismic dataset that was recorded during the 2009 eruption of Redoubt Volcano to examine eruptive volcano seismicity. I show that the progression of magma through the conduit system at Redoubt could be readily tracked by the seismicity. Many of my interpretations benefited greatly from the numerous other datasets collected during the eruption. Rarely was there volcanic activity that did not manifest itself in some way seismically, however, resulting in a remarkably complete chronology within the seismic record of the 2009 eruption. I also use the Redoubt seismic dataset to study post-eruptive seismicity. During the year following the eruption there were a number of unexplained bursts of shallow seismicity that did not culminate in eruptive activity despite closely mirroring seismic signals that had preceded explosions less than a year prior. I show that these episodes of shallow seismicity were in fact related to volcanic processes much deeper in the volcanic edifice by demonstrating that earthquakes that were related to magmatic activity during the eruption were also present during the renewed shallow unrest. These results show that magmatic processes can continue for many months after eruptions end, suggesting that volcanoes can stay active for much longer than previously thought. In the final chapter I characterize volcanic earthquakes on a much broader scale by analyzing a decade of continuous seismic data across 46 volcanoes in the Aleutian arc to search for regional-scale trends in volcano seismicity. I find that volcanic earthquakes below 20 km depth are much more common in the central region of the arc than they are in the eastern and western regions. I tie these observations to trends in magma geochemistry and regional tectonic features, and present two hypotheses to explain what could control volcanism in the Aleutian arc

An assessment of Sn-W-Nb-Ta oxide minerals from the Bugesera district of Rwanda and geological context

The Sn‐W‐Nb‐Ta oxide minerals of Rwanda are rarely found in the same area and predominantly occur in different deposits. Gatumba is known for its pegmatite related Nb‐Ta, and Sn mineralisation, Nyakabingo for its hydrothermal vein type W mineralisation, and Rutongo for its hydrothermal vein type Sn mineralisation. Very little geological research has been performed on the Bugesera district in Rwanda. Therefore, the aim of this study is to enhance the knowledge base on the Bugesera district by studying four mining areas (Nyagasagara, Gakurazo, Kageyo and Kageyo Extension) on the Hard Metal Rwanda (HMR) license, their locations relative to regional structures and G4 granites, and the mineral grade at each of the deposits. The mineralogy and mineral chemistry were only studied on the concentrate material from Nyagasagara, for comparison with literature and to determine whether the mineralisation was primary or secondary. The HMR license is located in between the Bugesera granite and the Bugesera syncline fold. Nyagasagara and Kageyo occur adjacent (< 4km) to known large scale structures, granites and/or pegmatites, Gakurazo is located in between Nyagasagara and Kageyo, and the Kageyo Extension is located on the rim of the Bugesera granite. No outcrops of granite and/or pegmatite were observed at any of the sites. The highest mineral grade was recorded at Nyagasagara Tunnel 1 (5.56% cassiterite) with the lowest grade recorded at Kageyo and Kageyo Extension (0.01% coltan). Around 60% of the cassiterite grains from Nyagasagara, reports to the coarser size fraction of +4 mm and +2 mm, with the shape of the grains ranging from angular to very angular. Cassiterite is the only oxide mineral of interest present at Nyagasagara, as confirmed by the whole rock chemistry and optical microscopy on the concentrate samples from Nyagasagara. The mineral chemistry of the cassiterite plots in the rare element granite and pegmatite field on the binary Nb + Ta and Fe + Mn diagram. Most of the cassiterite contains more Nb compared to Ta (Nb>Ta) and minor Fe2O3. The cassiterite also contained numerous coltan inclusions and exsolution products. This study concludes that the HMR license area is situated in a suitable regional geological setting for Sn‐ W‐Ta‐Nb oxide minerals to be found. However, the Nyagasagara deposit is an eluvial deposit consisting of only cassiterite minerals, which have a magmatic origin, believed to be related to rare element granites.MT 201

An assessment of Sn-W-Nb-Ta oxide minerals from the Bugesera district of Rwanda and geological context

The Sn‐W‐Nb‐Ta oxide minerals of Rwanda are rarely found in the same area and predominantly occur in different deposits. Gatumba is known for its pegmatite related Nb‐Ta, and Sn mineralisation, Nyakabingo for its hydrothermal vein type W mineralisation, and Rutongo for its hydrothermal vein type Sn mineralisation. Very little geological research has been performed on the Bugesera district in Rwanda. Therefore, the aim of this study is to enhance the knowledge base on the Bugesera district by studying four mining areas (Nyagasagara, Gakurazo, Kageyo and Kageyo Extension) on the Hard Metal Rwanda (HMR) license, their locations relative to regional structures and G4 granites, and the mineral grade at each of the deposits. The mineralogy and mineral chemistry were only studied on the concentrate material from Nyagasagara, for comparison with literature and to determine whether the mineralisation was primary or secondary. The HMR license is located in between the Bugesera granite and the Bugesera syncline fold. Nyagasagara and Kageyo occur adjacent (< 4km) to known large scale structures, granites and/or pegmatites, Gakurazo is located in between Nyagasagara and Kageyo, and the Kageyo Extension is located on the rim of the Bugesera granite. No outcrops of granite and/or pegmatite were observed at any of the sites. The highest mineral grade was recorded at Nyagasagara Tunnel 1 (5.56% cassiterite) with the lowest grade recorded at Kageyo and Kageyo Extension (0.01% coltan). Around 60% of the cassiterite grains from Nyagasagara, reports to the coarser size fraction of +4 mm and +2 mm, with the shape of the grains ranging from angular to very angular. Cassiterite is the only oxide mineral of interest present at Nyagasagara, as confirmed by the whole rock chemistry and optical microscopy on the concentrate samples from Nyagasagara. The mineral chemistry of the cassiterite plots in the rare element granite and pegmatite field on the binary Nb + Ta and Fe + Mn diagram. Most of the cassiterite contains more Nb compared to Ta (Nb>Ta) and minor Fe2O3. The cassiterite also contained numerous coltan inclusions and exsolution products. This study concludes that the HMR license area is situated in a suitable regional geological setting for Sn‐ W‐Ta‐Nb oxide minerals to be found. However, the Nyagasagara deposit is an eluvial deposit consisting of only cassiterite minerals, which have a magmatic origin, believed to be related to rare element granites.MT 201