Research ArticleGEOPHYSICS

Gravitational collapse of Mount Etna’s southeastern flank

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Science Advances  10 Oct 2018:
Vol. 4, no. 10, eaat9700
DOI: 10.1126/sciadv.aat9700
  • Fig. 1 Morphologic map of Mount Etna including tectonic features of the southeastern flank.

    Onshore topography in gray and offshore bathymetry in green to blue colors. Contour line interval is 300 m. Main features are shown as dashed (24) and solid (38) black lines. The thick gray line delineates the coastline. The orange rectangle marks the location of the seafloor geodetic network.

  • Fig. 2 Seafloor deformation across the fault that marks the offshore southern boundary of Mount Etna’s unstable flank, as recorded by the network of five autonomous monitoring transponders.

    (A and B) Relative changes in distances between transponder pairs (blue and green colors indicate active interrogation and passive response of acoustic signals, respectively) and relative vertical displacement between transponder pairs (gray line, 3-day moving average). Time series for all other transponder pairs are shown in figs. S2 and S3. (C) Map view of relative distance changes within the array during the observation period plotted on gray-shaded bathymetry (see Fig. 1 for location). Black numbers indicate transponder numbers.

  • Fig. 3 Eastward displacement of the southeastern flank of Mount Etna from April 2016 to July 2017.

    The map is obtained by integrating GPS and InSAR analysis using the SISTEM method (28). White dashed lines show principal faults. Dots show locations of the seafloor geodetic transponders.

  • Fig. 4 Shoreline-crossing fault slip representation of Mount Etna’s southeastern flank movement.

    Populated areas are obtained from a Landsat-8 classification on a 30 m by 30 m grid (Landsat-8 image courtesy of the U.S. Geological Survey). Bold lines represent main active features during the observation period.

  • Table 1 Characteristics of the May 2017 event for all fault crossing baselines.

    The 1 − σ value is based on the pre-event signal. Fault slip is calculated for three possible fault traces and the corresponding angle α of the baselines to the fault. The resulting mean slip from all baselines is 3.93 cm.

    Crossing
    baseline
    Baseline
    length
    Length
    change
    1 − σα1α2αmeanSlip1Slip2Mean slip
    (m)(cm)(cm)(°)(°)(°)(cm)(cm)(cm)
    1–2368.357−1.090.5567.272.269.72.823.573.15
    2–4804.192−3.320.8334.439.436.94.024.304.15
    4–5688.623−2.880.6643.648.646.13.984.364.16
    1–5350.7190.620.5194.999.997.47.223.594.79
    3–41253.642−3.461.545.510.58.03.473.513.49
    1–3699.045−3.861.610.55.53.03.863.873.86
    Mean slip:4.233.873.93

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/10/eaat9700/DC1

    Supplementary Text

    Fig. S1. Close-up bathymetric map and seismic image of the area with the seafloor geodetic network.

    Fig. S2. Relative changes in distances for all 10 baselines during the entire observation period from April 2016 to July 2017.

    Fig. S3. Cosine relationship between the relative distance shortening and lengthening during the May 2017 event and the angle at which the baselines cut the fault trace.

    Fig. S4. Relative pressure differences for the entire observation period (10-day moving average) between individual transponder pairs.

    Fig. S5. GPS displacements referring to the April 2016 to July 2017 comparison.

    Fig. S6. Ascending 31 March 2016 to 30 July 2017 and descending 6 April 2016 to 30 July 2017 Sentinel-1 phase interferograms.

    Fig. S7. East, north, and up displacement components resulting from the SISTEM integration.

    Fig. S8. Ground displacements along the LOS across the study area measured by both Sentinel 1A and 1B satellites with a 6-day interval.

    Reference (40)

  • Supplementary Materials

    This PDF file includes:

    • Supplementary Text
    • Fig. S1. Close-up bathymetric map and seismic image of the area with the seafloor geodetic network.
    • Fig. S2. Relative changes in distances for all 10 baselines during the entire observation period from April 2016 to July 2017.
    • Fig. S3. Cosine relationship between the relative distance shortening and lengthening during the May 2017 event and the angle at which the baselines cut the fault trace.
    • Fig. S4. Relative pressure differences for the entire observation period (10-day moving average) between individual transponder pairs.
    • Fig. S5. GPS displacements referring to the April 2016 to July 2017 comparison.
    • Fig. S6. Ascending 31 March 2016 to 30 July 2017 and descending 6 April 2016 to 30 July 2017 Sentinel-1 phase interferograms.
    • Fig. S7. East, north, and up displacement components resulting from the SISTEM integration.
    • Fig. S8. Ground displacements along the LOS across the study area measured by both Sentinel 1A and 1B satellites with a 6-day interval.
    • Reference (40)

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