Investigation of horizontal crustal movements in Iceland using a modulated light-beam device

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Celebration Schedule 2014 (Friday)

Full presentation schedule for Celebration, Friday, May 2, 201

Crustal deformation in extensional regimes: Iceland, Nevada and SW Turkey

In 1991 a 23-point, 30 x 25 km, GPS geodetic network was established in the Hengill ridge-ridge-transform triple junction, SW Iceland. The GPS data were processed using the Bernese V3.2 software. The ambiguity-fixed solution yielded scaled formal errors of less than 1 cm in the horizontal and about 1 cm in the vertical. The effect of ocean loading on the vertical component of the GPS measurements, a hither-to ignored effect in GPS data, was examined and found to be negligible for surveys of this type. Extensional deformation processes in the western Basin and Range province were studied by analysing the co- and postseismic deformation associated with the 1954 Rainbow Mountain - Fairview Peak - Dixie Valley sequence of M>6.0 earthquakes. Levelling and triangulation data which constrain the coseismic deformation are fitted well by modelling uniform slip on rectangular planar dislocations embedded in an elastic half-space. The best-fitting fault geometries dip at 50 to 80 and extend to depths of 8 to 14 km. A simultaneous inversion of the triangulation and levelling data which spanned the coseismic period reveals that slip determined geodetically tends to be equal to, or greater than, the surface offsets. Using the single value decomposition method to invert the data allowed determination of where the coseismic slip was resolvable given the data distribution. The static stresses changes induced by each earthquake in the 1954 sequence were calculated using the source models derived from the geodetic modelling. After the first earthquake each event in the 1954 sequence was preceded by a static stress increase of 104 to 105 Pa. Thus, it appears that static stresses may have played an important role in triggering the later earthquakes. The vertical postseismic deformation which followed the earthquakes was modelled assuming stress redistribution in the Earth's crust through viscous flow in the lower crust. Calculation of surface deformation caused by the analastic response to a normal faulting earthquake was performed using the finite element method. The viscosity which best fit the postseismic levelling data was 1x10(^20) Pa s at depths of 10 to 30 km. GPS measurements made between 1988 and 1992 show that north-south aseismic extension within SW Turkey is occurring at rates of 11.7+5 mm/yr. The deformation extension was modelled along 2-dimensional north-south profiles using the finite element method. These calculations show that the postseismic deformation created by eight earthquakes of Ms6.5 and greater within SW Turkey this century accounts for 10% of the north-south extension rate measured by GPS. The rest can be explained as postseismic deformation from earthquakes in earlier centuries. Modelling indicates that north-south extension rates decrease from west to east across the province. Reoccupation of the GPS network in the year 2000 will yield a clear regional strain signal, given the errors of the 1989 survey

Computational Sociolinguistics: A Survey

Language is a social phenomenon and variation is inherent to its social nature. Recently, there has been a surge of interest within the computational linguistics (CL) community in the social dimension of language. In this article we present a survey of the emerging field of "Computational Sociolinguistics" that reflects this increased interest. We aim to provide a comprehensive overview of CL research on sociolinguistic themes, featuring topics such as the relation between language and social identity, language use in social interaction and multilingual communication. Moreover, we demonstrate the potential for synergy between the research communities involved, by showing how the large-scale data-driven methods that are widely used in CL can complement existing sociolinguistic studies, and how sociolinguistics can inform and challenge the methods and assumptions employed in CL studies. We hope to convey the possible benefits of a closer collaboration between the two communities and conclude with a discussion of open challenges.Comment: To appear in Computational Linguistics. Accepted for publication: 18th February, 201

RRS Discovery Cruise 381, 28 Aug - 03 Oct 2012. Ocean Surface Mixing, Ocean Submesoscale Interaction Study (OSMOSIS)

Cruise D381 was made in support of NERC's Ocean Surface Boundary Layer theme action programme, OSMOSIS (Ocean Surface Mixing, Ocean Sub-mesoscale Interaction Study). The ocean surface boundary layer (OSBL) deepens in response to convective, wind and surface wave forcing, which produce three-dimensional turbulence that entrains denser water, deepening the layer. The OSBL shoals in response to solar heating and to mesoscale and sub-mesoscale motions that adjust lateral buoyancy gradients into vertical stratification. Recent and ongoing work is revolutionising our view of both the deepening and shoaling processes: new processes are coming into focus that are not currently recognised in model parameterisation schemes. In OSMOSIS we have a project which integrates observations, modelling studies and parameterisation development to deliver a step change in modelling of the OSBL. The OSMOSIS overall aim is to develop new, physically based and observationally supported, parameterisations of processes that deepen and shoal the OSBL, and to implement and evaluate these parameterisations in a state-of-the-art global coupled climate model, facilitating improved weather and climate predictions. Cruise D381 was split into two legs D381A and a process study cruise D381B. D381A partly deployed the OSMOSIS mooring array and two gliders for long term observations near the Porcupine Abyssal Plain Observatory. D381B firstly completed mooring and glider deployment work begun during the preceding D381A cruise. D381B then carried out several days of targetted turbulence profiling looking at changes in turbulent energy dissipation resulting from the interation of upper ocean fluid structures such as eddies, sub-mesoscale filaments and Langmuir cells with surface wind and current shear. Finally D381B conducted two spatial surveys with the towed SeaSoar vehicle to map and diagnose the mesoscale and sub-mesoscale flows, which, unusually, are the `large scale' background in which this study sits

RRS Discovery Cruise 381, 28 Aug - 03 Oct 2012. Ocean Surface Mixing, Ocean Submesoscale Interaction Study (OSMOSIS)

Cruise D381 was made in support of NERC's Ocean Surface Boundary Layer theme action programme, OSMOSIS (Ocean Surface Mixing, Ocean Sub-mesoscale Interaction Study). The ocean surface boundary layer (OSBL) deepens in response to convective, wind and surface wave forcing, which produce three-dimensional turbulence that entrains denser water, deepening the layer. The OSBL shoals in response to solar heating and to mesoscale and sub-mesoscale motions that adjust lateral buoyancy gradients into vertical stratification. Recent and ongoing work is revolutionising our view of both the deepening and shoaling processes: new processes are coming into focus that are not currently recognised in model parameterisation schemes. In OSMOSIS we have a project which integrates observations, modelling studies and parameterisation development to deliver a step change in modelling of the OSBL. The OSMOSIS overall aim is to develop new, physically based and observationally supported, parameterisations of processes that deepen and shoal the OSBL, and to implement and evaluate these parameterisations in a state-of-the-art global coupled climate model, facilitating improved weather and climate predictions. Cruise D381 was split into two legs D381A and a process study cruise D381B. D381A partly deployed the OSMOSIS mooring array and two gliders for long term observations near the Porcupine Abyssal Plain Observatory. D381B firstly completed mooring and glider deployment work begun during the preceding D381A cruise. D381B then carried out several days of targetted turbulence profiling looking at changes in turbulent energy dissipation resulting from the interation of upper ocean fluid structures such as eddies, sub-mesoscale filaments and Langmuir cells with surface wind and current shear. Finally D381B conducted two spatial surveys with the towed SeaSoar vehicle to map and diagnose the mesoscale and sub-mesoscale flows, which, unusually, are the `large scale' background in which this study sits

Detection of Tephra Layers in Antarctic Sediment Cores with Hyperspectral Imaging

Tephrochronology uses recognizable volcanic ash layers (from airborne pyroclastic deposits, or tephras) in geological strata to set unique time references for paleoenvironmental events across wide geographic areas. This involves the detection of tephra layers which sometimes are not evident to the naked eye, including the so-called cryptotephras. Tests that are expensive, time-consuming, and/or destructive are often required. Destructive testing for tephra layers of cores from difficult regions, such as Antarctica, which are useful sources of other kinds of information beyond tephras, is always undesirable. Here we propose hyperspectral imaging of cores, Self-Organizing Map (SOM) clustering of the preprocessed spectral signatures, and spatial analysis of the classified images as a convenient, fast, non-destructive method for tephra detection. We test the method in five sediment cores from three Antarctic lakes, and show its potential for detection of tephras and cryptotephras.info:eu-repo/semantics/publishedVersio

Quantitative analysis of web content in support of qualitative research: examples from the study of post-Soviet de facto states

In recent years, the internet has been increasingly adopted as a key means of communication by local authorities, organisations and news media throughout the post-Soviet context. This has led to the creation and on-line publication of content that is routinely consulted and quoted by scholars of area studies, who, however, seemingly approach the web as an inordinate mass of content that can be superficially explored thanks to search engines and meaningful keywords. Structured analysis of content is still uncommon in area studies for a few reasons: it is considered to be time consuming, difficult to learn and, fundamentally, relevant datasets are usually not readily available. This paper briefly presents how to overcome these obstacles by introducing an open source package developed by the author that facilitates the creation of structured textual datasets from web content, and allows for basic word frequency analysis in a straightforward web interface. This article argues in favour of a wider use of quantitative methods based on the analysis of word frequency in textual datasets extracted from the internet as a starting point for in depth research with established qualitative methods. The examples presented in this paper relate to the study of post-Soviet de facto states

ATS-5 trilateration support

The development of an L-band trilateration network capable of locating the ATS-5 satellite, determining the satellite's orbital elements, and predicting the satellite position was investigated. An automatic tone-code ranging transponder was used to compare ranging measurements and communications reliability for the VHF and L-band. The L-band transponder network, analytical techniques, and the determination of the Kepler orbit parameters are described along with the calibration procedures, operation procedures, and verification of trilateration position