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  • Artikel  (2)
  • Seismological Society of America  (1)
  • Wiley  (1)
  • 2015-2019  (2)
  • Physik  (2)
  • 1
    Publikationsdatum: 2019
    Beschreibung: Abstract The ionized upper portion of the atmosphere, the ionosphere, affects radio signals traveling between satellites and the ground. This degrades the performance of satellite navigation, surveillance, and communication systems. Techniques to measure and mitigate ionospheric effects and in particular to measure the total electron content (TEC) are therefore required. TEC is usually determined by analyzing the differential delay experienced by dual‐frequency signals. Here we demonstrate a technique which enables TEC to be derived using single‐frequency signals passing between geostationary satellites and terrestrial Global Positioning System (GPS) receivers. Geostationary satellites offer the key advantage that the raypaths are not moving and hence are easier to interpret than standard GPS TEC. Daily TEC time series are derived for three ground receivers from Europe over the year 2015. The technique is validated by correlation analysis both between pairs of ground receiver observations and between ground receivers and independent ionosonde observations. The correlation between pairs of receivers over a year shows good agreement. Good agreement was also seen between the TEC time series and ionosonde data, suggesting the technique is reliable and routinely produces realistic ionospheric information. The technique is not suitable for use on every GPS receiver type because drift in derived TEC values was observed for profiles calculated using receivers without links to highly stable clocks. The demonstrated technique has the potential to become a routine method to derive TEC, helping to map the ionosphere in real time and to mitigate ionospheric effects on radio systems.
    Print ISSN: 0048-6604
    Digitale ISSN: 1944-799X
    Thema: Geologie und Paläontologie , Physik
    Publiziert von Wiley im Namen von American Geophysical Union (AGU).
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2019-11-19
    Beschreibung: Prominent scarps on Pinedale glacial surfaces along the eastern base of the Teton Range confirm latest Pleistocene to Holocene surface-faulting earthquakes on the Teton fault, but the timing of these events is only broadly constrained by a single previous paleoseismic study. We excavated two trenches at the Leigh Lake site near the center of the Teton fault to address open questions about earthquake timing and rupture length. Structural and stratigraphic evidence indicates two surface-faulting earthquakes at the site that postdate deglacial sediments dated by radiocarbon and optically stimulated luminescence to ∼10–11  ka. Earthquake LL2 occurred at ∼10.0  ka (9.7–10.4? ka; 95% confidence range) and LL1 at ∼5.9  ka (4.8–7.1? ka; 95%). LL2 predates an earthquake at ∼8  ka identified in the previous paleoseismic investigation at Granite Canyon. LL1 corresponds to the most recent Granite Canyon earthquake at ∼4.7–7.9  ka (95% confidence range). Our results are consistent with the previously documented long-elapsed time since the most recent Teton fault rupture and expand the fault’s earthquake history into the early Holocene.
    Print ISSN: 0037-1106
    Digitale ISSN: 1943-3573
    Thema: Geologie und Paläontologie , Physik
    Standort Signatur Erwartet Verfügbarkeit
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