Seismic Characteristics of the Largest Measured Subglacial Flood from the Eastern Skaftá cauldron, Iceland
Subglacial floods cause seismic tremors that can be located and tracked in space and time using a seismic array. Here, we shed light on the generating mechanisms of the seismic signals observed during the largest measured flood from the eastern Skaftá cauldron in the Vatnajökull ice cap, Iceland. We...
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ftcopernicus:oai:publications.copernicus.org:egusphere105149 2023-11-05T03:42:07+01:00 Seismic Characteristics of the Largest Measured Subglacial Flood from the Eastern Skaftá cauldron, Iceland Eibl, Eva P. S. Vogfjörd, Kristin S. Ófeigsson, Benedikt G. Roberts, Matthew J. Bean, Christopher J. Jones, Morgan T. Bergsson, Bergur H. 2023-10-05 application/pdf https://doi.org/10.5194/egusphere-2022-644 https://egusphere.copernicus.org/preprints/2022/egusphere-2022-644/ eng eng doi:10.5194/egusphere-2022-644 https://egusphere.copernicus.org/preprints/2022/egusphere-2022-644/ eISSN: Text 2023 ftcopernicus https://doi.org/10.5194/egusphere-2022-644 2023-10-09T16:24:16Z Subglacial floods cause seismic tremors that can be located and tracked in space and time using a seismic array. Here, we shed light on the generating mechanisms of the seismic signals observed during the largest measured flood from the eastern Skaftá cauldron in the Vatnajökull ice cap, Iceland. We track the propagation of the flood in 2015 using two seismic arrays and a local seismic network in combination with GPS, hydrological, and geochemical data. We find that as the water drained from the subglacial lake beneath the cauldron, families of icequakes were generated in the area around the cauldron, while the glacier surface gradually subsided by more than 100 m. We detected a several-hours-long, non-harmonic tremor and high-frequency transient events migrating downglacier, following the subglacial flood front. We suggest that this tremor is composed of repeating, closely spaced icequakes that were generated as the glacier was being lifted, cracked, and deformed, thus enabling the subglacial water flow. When the lake had largely drained, the pressure within the underlying hydrothermal system dropped. At this time, we recorded minute-long tremor bursts emanating from the cauldron area, followed by an hour-long harmonic tremor each. We interpret these as being caused by hydrothermal explosions in the geothermal system within the cauldron and as being vigorous boiling in the crustal rocks, respectively, which is an interpretation corroborated by floodwater geochemical signals. Finally, the flood also led to detectable tremor due to more energetic flow in the rapids near Sveinstindur in the Skaftá river. We conclude that the flood generated five different seismic signal types that can be associated with five different geophysical processes, including the wide spectrum from brittle failure and explosions to boiling and turbulent flow. Text glacier Ice cap Iceland Vatnajökull Copernicus Publications: E-Journals |
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English |
description |
Subglacial floods cause seismic tremors that can be located and tracked in space and time using a seismic array. Here, we shed light on the generating mechanisms of the seismic signals observed during the largest measured flood from the eastern Skaftá cauldron in the Vatnajökull ice cap, Iceland. We track the propagation of the flood in 2015 using two seismic arrays and a local seismic network in combination with GPS, hydrological, and geochemical data. We find that as the water drained from the subglacial lake beneath the cauldron, families of icequakes were generated in the area around the cauldron, while the glacier surface gradually subsided by more than 100 m. We detected a several-hours-long, non-harmonic tremor and high-frequency transient events migrating downglacier, following the subglacial flood front. We suggest that this tremor is composed of repeating, closely spaced icequakes that were generated as the glacier was being lifted, cracked, and deformed, thus enabling the subglacial water flow. When the lake had largely drained, the pressure within the underlying hydrothermal system dropped. At this time, we recorded minute-long tremor bursts emanating from the cauldron area, followed by an hour-long harmonic tremor each. We interpret these as being caused by hydrothermal explosions in the geothermal system within the cauldron and as being vigorous boiling in the crustal rocks, respectively, which is an interpretation corroborated by floodwater geochemical signals. Finally, the flood also led to detectable tremor due to more energetic flow in the rapids near Sveinstindur in the Skaftá river. We conclude that the flood generated five different seismic signal types that can be associated with five different geophysical processes, including the wide spectrum from brittle failure and explosions to boiling and turbulent flow. |
format |
Text |
author |
Eibl, Eva P. S. Vogfjörd, Kristin S. Ófeigsson, Benedikt G. Roberts, Matthew J. Bean, Christopher J. Jones, Morgan T. Bergsson, Bergur H. |
spellingShingle |
Eibl, Eva P. S. Vogfjörd, Kristin S. Ófeigsson, Benedikt G. Roberts, Matthew J. Bean, Christopher J. Jones, Morgan T. Bergsson, Bergur H. Seismic Characteristics of the Largest Measured Subglacial Flood from the Eastern Skaftá cauldron, Iceland |
author_facet |
Eibl, Eva P. S. Vogfjörd, Kristin S. Ófeigsson, Benedikt G. Roberts, Matthew J. Bean, Christopher J. Jones, Morgan T. Bergsson, Bergur H. |
author_sort |
Eibl, Eva P. S. |
title |
Seismic Characteristics of the Largest Measured Subglacial Flood from the Eastern Skaftá cauldron, Iceland |
title_short |
Seismic Characteristics of the Largest Measured Subglacial Flood from the Eastern Skaftá cauldron, Iceland |
title_full |
Seismic Characteristics of the Largest Measured Subglacial Flood from the Eastern Skaftá cauldron, Iceland |
title_fullStr |
Seismic Characteristics of the Largest Measured Subglacial Flood from the Eastern Skaftá cauldron, Iceland |
title_full_unstemmed |
Seismic Characteristics of the Largest Measured Subglacial Flood from the Eastern Skaftá cauldron, Iceland |
title_sort |
seismic characteristics of the largest measured subglacial flood from the eastern skaftá cauldron, iceland |
publishDate |
2023 |
url |
https://doi.org/10.5194/egusphere-2022-644 https://egusphere.copernicus.org/preprints/2022/egusphere-2022-644/ |
genre |
glacier Ice cap Iceland Vatnajökull |
genre_facet |
glacier Ice cap Iceland Vatnajökull |
op_source |
eISSN: |
op_relation |
doi:10.5194/egusphere-2022-644 https://egusphere.copernicus.org/preprints/2022/egusphere-2022-644/ |
op_doi |
https://doi.org/10.5194/egusphere-2022-644 |
_version_ |
1781699004768190464 |