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On the origin of the surname element Mág
Get PDFThis paper seeks to explain how Mac (gen. sg./nom. pl. Meic) became Mág (gen. sg./nom. pl. Méig) in some surnames. It is argued that the form Mág/Méig was already in existence in the Middle Irish period, though this is obscured by contemporary orthographical practice
Full-Waveform based methods for Microseismic Monitoring Operations: an Application to Natural and Induced Seismicity in the Hengill Geothermal Area, Iceland
Get PDFGeothermal systems in the Hengill volcanic area, SW Iceland, started to be exploited for electrical power and heat production since the late 1960s. Today the two largest operating geothermal power plants are located at Nesjavellir and Hellisheiði. This area is a complex tectonic and geothermal site, located at the triple junction between the Reykjanes Peninsula (RP), the Western Volcanic Zone (WVZ), and the South Iceland Seismic Zone (SISZ). The region is seismically highly active with several thousand earthquakes located yearly. The origin of such earthquakes may be either natural or anthropogenic. The analysis of microseismicity can provide useful information on natural active processes in tectonic, geothermal and volcanic environments as well as on physical mechanisms governing induced events. Here, we investigate the microseismicity occurring in Hengill area, using a very dense broadband seismic monitoring network deployed in Hellisheiði since November 2018, and apply sophisticated full-waveform based method for detection and
location. Improved locations and first characterization indicate that it is possible to identify different types of microseismic clusters, which are associated with either production/ injection or the tectonic setting of the geothermal area
Virtual sources of body waves from noise correlation in a mineral exploration context
Get PDFThe extraction of body waves from passive seismic recordings has great potential for monitoring and imaging applications. The low environmental impact, low cost, and high accessibility of passive techniques makes them especially attractive as replacement or complementary techniques to active-source exploration. There still, however, remain
many challenges with body-wave extraction, mainly the strong dependence on local seismic sources necessary to create high-frequency body-wave energy. Here, we present the Marathon dataset collected in September 2018, which consists of 30 days of continuous recordings from a dense surface array of 1020 single vertical-component geophones deployed over a mineral exploration block. First, we use a cross-correlation beamforming technique to evaluate the wavefield each minute and discover that the local highway and railroad traffic are the primary sources of high-frequency body-wave
energy. Next, we demonstrate how selective stacking of cross-correlation functions during periods where vehicles and trains are passing near the array reveals strong bodywave arrivals. Based on source station geometry and the estimated geologic structure,we interpret these arrivals as virtual refractions due to their high velocity and linear
moveout. Finally, we demonstrate how the apparent velocity of these arrivals along the array contains information about the local geologic structure, mainly the major dipping
layer. Although vehicle sources illuminating array in a narrow azimuth may not seem ideal for passive reflection imaging, we expect this case will be commonly encountered
and should serve as a good dataset for the development of new techniques in this domain
Review of Riggs, Pádraigín (ed.): Tadhg Dall Ó hUiginn: his historical and literary context (London, 2010).
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Review of Kailuweit, Rolf, Künkel, Lisann and Staudinger, Eva (eds), Applying and Expanding Role and Reference Grammar (Freiburg, 2018)
Get PDFThe dynamics of a long-lasting effusive eruption modulated by Earth tides
Get PDFDeciphering eruptive dynamics in near-real time is essential when dealing with hazard assessment and population evacuation. Recognition of specific patterns in time-series measured during volcanic activity may help decipher distinctive behavior at active volcanoes, providing insights into the underlying driving mechanisms. Multi-parameter data sets usually agree on the overall trend characterizing the temporal evolution of an eruption providing insights into the first-order eruptive dynamics. However, second-order variations detected in different data sets remain often poorly understood. The 2014-2015 Holuhraun eruption (Iceland) offers an excellent opportunity to investigate the dynamics of a long-lasting effusive eruption. We analyze the seismic tremor and the volcanic radiated power emitted by the lava field during the 6 months of the eruption using Singular Spectrum Analysis (SSA). In both geophysical time-series, we identify periods from ∼5 to ∼32 days coinciding with periods of Earth tides. Here we show that ∼50% of both signals are composed of tidal periods suggesting that magma movements follow frequencies imposed by lunisolar forces within the crust and at Earth’s surfac
Very high energy gamma-ray emission from two blazars of unknown redshift and upper limits on their distance
Get PDFWe report on the detection of very high energy (VHE; E > 100 GeV) gamma-ray emission from the BL Lac objects KUV 00311-1938 and PKS 1440-389 with the High Energy Stereoscopic System (H.E.S.S.). H.E.S.S. observations were accompanied or preceded by multiwavelength observations with Fermi/LAT, XRT and UVOT onboard the Swift satellite, and ATOM. Based on an extrapolation of the Fermi/LAT spectrum towards the VHE gamma-ray regime, we deduce a 95 per cent confidence level upper limit on the unknown redshift of KUV 00311-1938 of z < 0.98 and of PKS 1440-389 of z < 0.53. When combined with previous spectroscopy results, the redshift of KUV 00311-1938 is constrained to 0.51 <= z < 0.98 and of PKS 1440-389 to 0.14 <= z < 0.53
Simultaneous observations of the blazar PKS 2155−304 from ultra-violet to TeV energies
Get PDFHere we report the results of the first ever contemporaneous multi-wavelength observation campaign on the BL Lac object PKS 2155−304 involving Swift, NuSTAR, Fermi-LAT, and H.E.S.S. The use of these instruments allows us to cover a broad energy range, which is important for disentangling the different radiative mechanisms. The source, observed from June 2013 to October 2013, was found in a low flux state with respect to previous observations but exhibited highly significant flux variability in the X-rays. The high-energy end of the synchrotron spectrum can be traced up to 40 keV without significant contamination by high-energy emission. A one-zone synchrotron self-Compton model was used to reproduce the broadband flux of the source for all the observations presented here but failed for previous observations made in April 2013. A lepto-hadronic solution was then explored to explain these earlier observational results