@article{EiblMuellerWalteretal.2021, author = {Eibl, Eva P. S. and M{\"u}ller, Daniel and Walter, Thomas R. and Allahbakhshi, Masoud and Jousset, Philippe and Hersir, Gylfi P{\´a}ll and Dahm, Torsten}, title = {Eruptive cycle and bubble trap of Strokkur Geyser, Iceland}, series = {Journal of geophysical research : JGR. B: Solid earth}, volume = {126}, journal = {Journal of geophysical research : JGR. B: Solid earth}, number = {4}, publisher = {Wiley}, address = {Hoboken, NJ}, issn = {2169-9313}, doi = {10.1029/2020JB020769}, pages = {20}, year = {2021}, abstract = {The eruption frequency of geysers can be studied easily on the surface. However, details of the internal structure including possible water and gas filled chambers feeding eruptions and the driving mechanisms often remain elusive. We used a multidisciplinary network of seismometers, video cameras, water pressure sensors and one tiltmeter to study the eruptive cycle, internal structure, and mechanisms driving the eruptive cycle of Strokkur geyser in June 2018. An eruptive cycle at Strokkur always consists of four phases: (1) Eruption, (2) post-eruptive conduit refilling, (3) gas filling of the bubble trap, and (4) regular bubble collapse at shallow depth in the conduit. For a typical single eruption 19 +/- 4 bubble collapses occur in Phase 3 and 8 +/- 2 collapses in Phase 4 at a mean spacing of 1.52 +/- 0.29 and 24.5 +/- 5.9 s, respectively. These collapses release latent heat to the fluid in the bubble trap (Phase 3) and later to the fluid in the conduit (Phase 4). The latter eventually reaches thermodynamic conditions for an eruption. Single to sextuple eruptions have similar spacings between bubble collapses and are likely fed from the same bubble trap at 23.7 +/- 4.4 m depth, 13-23 m west of the conduit. However, the duration of the eruption and recharging phase linearly increases likely due to a larger water, gas and heat loss from the system. Our tremor data provides documented evidence for a bubble trap beneath a pool geyser.}, language = {en} } @article{GreenfieldWinderRawlinsonetal.2022, author = {Greenfield, Tim and Winder, Tom and Rawlinson, Nicholas and Maclennan, John and White, Robert S. and {\´A}g{\´u}stsd{\´o}ttir, Thorbj{\"o}rg and Bacon, Conor Andrew and Brandsd{\´o}ttir, Bryndis and Eibl, Eva P. S. and Glastonbury-Southern, Esme and Gudnason, Egill {\´A}rni and Hersir, Gylfi P{\´a}ll and Hor{\´a}lek, Josef}, title = {Deep long period seismicity preceding and during the 2021 Fagradalsfjall eruption, Iceland}, series = {Bulletin of volcanology : official journal of the International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI)}, volume = {84}, journal = {Bulletin of volcanology : official journal of the International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI)}, number = {12}, publisher = {Springer}, address = {Berlin ; Heidelberg ; New York}, issn = {0258-8900}, doi = {10.1007/s00445-022-01603-2}, pages = {20}, year = {2022}, abstract = {We use a dense seismic network on the Reykjanes Peninsula, Iceland, to image a group of earthquakes at 10-12 km depth, 2 km north-east of 2021 Fagradalsfjall eruption site. These deep earthquakes have a lower frequency content compared to earthquakes located in the upper, brittle crust and are similar to deep long period (DLP) seismicity observed at other volcanoes in Iceland and around the world. We observed several swarms of DLP earthquakes between the start of the study period (June 2020) and the initiation of the 3-week-long dyke intrusion that preceded the eruption in March 2021. During the eruption, DLP earthquake swarms returned 1 km SW of their original location during periods when the discharge rate or fountaining style of the eruption changed. The DLP seismicity is therefore likely to be linked to the magma plumbing system beneath Fagradalsfjall. However, the DLP seismicity occurred similar to 5 km shallower than where petrological modelling places the near-Moho magma storage region in which the Fagradalsfjall lava was stored. We suggest that the DLP seismicity was triggered by the exsolution of CO2-rich fluids or the movement of magma at a barrier to the transport of melt in the lower crust. Increased flux through the magma plumbing system during the eruption likely adds to the complexity of the melt migration process, thus causing further DLP seismicity, despite a contemporaneous magma channel to the surface.}, language = {en} } @article{SudibyoEiblHainzletal.2022, author = {Sudibyo, Maria R. P. and Eibl, Eva P. S. and Hainzl, Sebastian and Hersir, Gylfi P{\´a}ll}, title = {Eruption Forecasting of Strokkur Geyser, Iceland, Using Permutation Entropy}, series = {Journal of geophysical research : Solid earth}, volume = {127}, journal = {Journal of geophysical research : Solid earth}, number = {10}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9313}, doi = {10.1029/2022JB024840}, pages = {15}, year = {2022}, abstract = {A volcanic eruption is usually preceded by seismic precursors, but their interpretation and use for forecasting the eruption onset time remain a challenge. A part of the eruptive processes in open conduits of volcanoes may be similar to those encountered in geysers. Since geysers erupt more often, they are useful sites for testing new forecasting methods. We tested the application of Permutation Entropy (PE) as a robust method to assess the complexity in seismic recordings of the Strokkur geyser, Iceland. Strokkur features several minute-long eruptive cycles, enabling us to verify in 63 recorded cycles whether PE behaves consistently from one eruption to the next one. We performed synthetic tests to understand the effect of different parameter settings in the PE calculation. Our application to Strokkur shows a distinct, repeating PE pattern consistent with previously identified phases in the eruptive cycle. We find a systematic increase in PE within the last 15 s before the eruption, indicating that an eruption will occur. We quantified the predictive power of PE, showing that PE performs better than seismic signal strength or quiescence when it comes to forecasting eruptions.}, language = {en} }