• Looking back at the Tonga eruption

    From ScienceDaily@1:317/3 to All on Fri Jan 27 21:30:34 2023
    Looking back at the Tonga eruption

    Date:
    January 27, 2023
    Source:
    Hokkaido University
    Summary:
    A 'back-projection' technique reveals new details of the volcanic
    eruption in Tonga that literally shook the world.


    Facebook Twitter Pinterest LinkedIN Email
    FULL STORY ==========================================================================
    A new analysis of seismic data recorded after the massively violent
    eruption of the underwater volcano Hunga Tonga-Hunga Ha'apai, on January
    15, 2022, has revealed new and useful information on the sequence of
    events. Kotaro Tarumi and Kazunori Yoshizawa at Hokkaido University
    discuss their methods and findings in an article in Earth and Planetary
    Science Letters.


    ==========================================================================
    "We showed that the eruption consisted of two distinct sequences
    of events, some of which occurred quasi-periodically in the first
    sequence. It will be worthwhile to investigate the mechanisms involved
    in such eruption cycles further," says seismologist and geophysicist
    Yoshizawa.

    The volcano generated seismic, tsunami and atmospheric waves that were
    recorded worldwide. Recent studies have estimated that it was one of
    the most energetic eruptions recorded by modern instruments.

    "Eruption episodes are difficult to analyse fully from seismic surface
    waves, but we have teased out more details using what are called
    teleseismic-P waves," says PhD student Tarumi. These are seismic waves
    that have travelled through the planet to locations distant from the
    eruption site. In this case, the team used seismic data collected from
    sites as far as at a 93-degree angle around the circumference of the
    planet.

    The team's "back-projection" analysis successfully detected the locations
    and timing of multiple explosions, even though P-waves from each eruption overlapped and were masked by other seismic signals and noises.

    The back-projection technique reverses the transmission of seismic
    signals to reveal details of a potential source that radiated seismic
    waves. It was originally developed and applied for imaging the source
    processes of large earthquakes, but is now proving equally applicable
    to large scale volcanic events.

    The results revealed that the sequence of eruptions occurred in two
    main parts.

    The first sequence began at 04:02 UTC on January 15, then escalated into
    major explosions at 04:15 UTC and 200 to 300 seconds after. The entire
    sequence lasted at least until 04:35 UTC. A second sequence of eruptions
    began about four hours later and continued from six to seven minutes,
    including a massive eruption at 08:31. Satellite imagery recorded the
    resulting dramatic ash cloud from the first eruption sequence, but until
    now the precise details of the underwater events have remained elusive.

    One interesting finding was that significant explosive eruptions
    intermittently occurred at 270 to 280 second intervals, a frequency
    suggesting a resonance effect with the atmosphere and the Earth. "This
    apparent agreement of the eruption cycle and the atmospheric resonant oscillation with the Earth could be coincidental, but it certainly
    deserves further exploration," Yoshizawa concludes.

    * RELATED_TOPICS
    o Matter_&_Energy
    # Albert_Einstein # Physics # Optics
    o Earth_&_Climate
    # Natural_Disasters # Volcanoes # Earthquakes
    o Fossils_&_Ruins
    # Early_Climate # Lost_Treasures
    * RELATED_TERMS
    o Caldera o Krakatoa o Volcanic_cone o Toba_catastrophe_theory
    o Volcanic_ash o Mount_St._Helens o Decade_Volcanoes o
    Volcanic_rock

    ========================================================================== Story Source: Materials provided by Hokkaido_University. Note: Content
    may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Kotaro Tarumi, Kazunori Yoshizawa. Eruption sequence of the
    2022 Hunga
    Tonga-Hunga Ha'apai explosion from back-projection of teleseismic
    P waves. Earth and Planetary Science Letters, 2023; 602: 117966
    DOI: 10.1016/j.epsl.2022.117966 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2023/01/230127131154.htm

    --- up 47 weeks, 4 days, 10 hours, 50 minutes
    * Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)