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  • 1
    Publication Date: 2020-02-12
    Description: [1] We compare observations of long-period seismic surface waves and free oscillations recorded by high-resolution long-base fluid tube tiltmeters and by nearby broadband seismometers after large earthquakes. The quality of the tiltmeter data is comparable to that of the best horizontal component seismic data, recording some of the gravest free oscillations of the Earth, as well as successive passages of seismic surface waves circling the globe. We compare the observations with theoretical seismograms and with theoretical tilt. The predicted and observed surface wave tilt waveforms are very similar provided that we take into account horizontal acceleration effects on the tiltmeter. Phase and amplitude anomalies between the waveforms are well explained by the theoretical transfer function of the instrument. Likewise, observed horizontal seismograms converted into tilt match the tiltmeter data very well. Long-base fluid tube tiltmeters could potentially contribute to obtain high-quality measurements of the long-period seismic spectrum.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 2
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    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Publication Date: 2023-05-23
    Description: During eruptions, volcanoes produce air-pressure waves inaudible for the human ear called infrasound, which are very helpful for detecting early signs of magma at the surface. Compared to violent ash-rich explosions, recording more discreet atmospheric disturbances from effusive eruptions remains a practical challenge. Wind and human activity are other powerful sources of unwanted infrasound noise masking volcanic ones. At Nyiragongo volcano (D.R. Congo), close to a one-million urban area, the drainage of the world’s largest lava lake concomitant with short-duration lava flows on its flank and the renewal of an effusive eruption within its crater a few months later were a series of major volcanic events in 2021, all monitored with infrasound sensors. First, we explore these records for characterizing the temporal and spatial evolution of the flank eruption on May 22, 2021. In a second step, we show evidence of the infrasonic rumbling of a nascent lava lake starting a few months later detected up to the volcano observatory facilities in Goma city center about 17 km from Nyiragongo’s crater. These results show remarkable local recordings of eruptive infrasound from rural and city-based stations and have significant implication for optimizing future monitoring efforts in a harsh field environment.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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