Summary
Speeded-up magnetic tape recordings of earthquake signals can be analyzed by means of an electronic sound spectrograph. The time-dependent spectrum of body waves obtained through transient analysis provides some insight into the physical properties of the earth's interior. In the short-period arrivals traveling through the outer core and inner core dispersion has been observed. A group velocity maximum has been found forP′ at periods between 1 and 2 seconds. The direct rayP′and the surface reflected phasePP convey more energy than the arrivalsP′ 2 andPcPP′ which, firstly, enter the outer core at incidence far from vertical, and secondly spend more time in the outer part of the fluid core.
Zusammenfassung
Magnetbandaufzeichnungen von Erdbebensignalen können, mit vervielfachter Geschwindigkeit wiedergegeben, mittels eines elektronischen Schallspektrographen analysiert werden. Das zeitabhängige Raumwellenspektrum, das man aus einer solchen Analyse nichtstationärer Vorgänge erhält, gibt einen gewissen Einblick in die physikalischen Eigenschaften des Erdinnern. So wurde im kurzperiodischen Anteil der Raumwellen, die durch den äusseren und inneren Erdkern gelaufen sind, Dispersion beobachtet. BeiP′ wurde im Periodenbereich zwischen 1 und 2 Sekunden ein Gruppengeschwindigkeitsmaximum gefunden. Der direkte StrahlP′ und die einmal an der Erdoberfläche reflektiertePP-Welle transportieren mehr Energie als die WellenphasenP′ 2 undPcPP′, die erstens in den äusseren Erdkern unter einem sehr grossen Inzidenzwinkel eindringen und zweitens eine längere Zeit benötigen, um den äusseren Teil des flüssigkeitsähnlichen Kerns zu durchlaufen.
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Lamont Geological Observatory Contribution No. 558.
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Landisman, M., Mueller, S., Bolt, B. et al. Transient analysis of seismic core phases. Geofisica Pura e Applicata 52, 41–52 (1962). https://doi.org/10.1007/BF01995998
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DOI: https://doi.org/10.1007/BF01995998